A method for corrosion protection and life recovery of marine salt spray environment service turboshaft engine overhaul system

Abstract

The application discloses a marine salt spray environment service turboshaft engine overhaul systematic corrosion protection and life recovery method, and relates to the technical field of aero-engine overhaul and remanufacturing, and comprises the following steps: corrosion damage detection is performed on a marine salt spray environment service turboshaft engine, a four-grade grading evaluation system of corrosion damage is established, macroscopic detection, microscopic detection and internal damage detection are adopted to realize quantitative characterization of corrosion damage, and corresponding grading disposal results are formed. The application constructs a marine environment engine overhaul systematic corrosion protection system, realizes integration of corrosion accurate evaluation, grading repair and gradient protection, cooperates with a chlorine ion whole-process management and control and a life prediction model, recovers the service life of the engine to the level of a new piece, reduces spare part cost and improves the reuse rate, simultaneously realizes data traceability through a consortium chain, meets airworthiness requirements and has industry popularization value.

Description

Technical Field

[0001] This invention relates to the field of aero-engine overhaul and remanufacturing technology, specifically to a method for systematic corrosion protection and life recovery of turboshaft engines operating in marine salt spray environments during overhaul. Background Technology

[0002] As the core power system of shipborne helicopters, maritime search and rescue helicopters, and general aviation helicopters on marine platforms, turboshaft engines operate for extended periods in the high-salt-spray, high-humidity, and high-chloride-ion-concentration marine atmospheric environment, making their corrosion failure risk significantly higher than in inland environments. Relevant statistics show that approximately 73% of failures in aviation equipment at coastal bases are related to corrosion and mold growth caused by the marine environment, with corrosion-related repair costs accounting for nearly 50% of total maintenance costs. Meanwhile, operational data from domestic shipborne helicopters indicates that the corrosion-related failure return rate for turboshaft engines operating in marine environments reaches as high as 42% within 1000 hours after a major overhaul. Among these failures, compressor blade pitting, hot-end component thermal corrosion, magnesium / aluminum alloy casing crevice corrosion, and stress corrosion cracking of bearings and transmission components are the main failure modes affecting engine reliability, service life, and overhaul costs. Therefore, conducting systematic technical research on corrosion protection and life recovery during engine overhauls in marine salt-spray environments is of great significance.

[0003] Currently, the industry generally adopts a discrete technical model of single-point repair + end-of-line protection for corrosion protection of turboshaft engines in marine environments during overhauls. This lacks a systematic, end-to-end management system that spans the entire process from incoming assessment to disassembly and cleaning, repair, protection, assembly, testing, and delivery. In terms of corrosion detection, methods such as fluorescent penetrant testing and visual inspection are insufficient for quantitative assessment of early micro-corrosion and internal damage. Regarding repair and protection, these are independent processes, making it difficult to simultaneously restore substrate performance and corrosion resistance, and resulting in insufficient durability of the protective layer. In terms of cleanliness control, inland environmental standards are still used, without establishing specific control mechanisms for chloride ion residue and secondary corrosion, leading to re-corrosion failure shortly after overhaul. Furthermore, the lack of a marine-specific remaining service life prediction model and a full-process data traceability system fails to meet the recordable and verifiable requirements for airworthiness certification. These problems result in an engine overhaul interval of only about 60% of that of a new part, with high spare parts costs and poor reliability, severely restricting the safety and economy of aviation equipment in marine environments.

[0004] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a method for systematic corrosion protection and life recovery of turboshaft engines operating in marine salt spray environments during overhaul, in order to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for systemic corrosion protection and life recovery of a turboshaft engine operating in a marine salt spray environment during overhaul, comprising the following steps: Corrosion damage detection was carried out on turboshaft engines operating in marine salt spray environment. A four-level classification assessment system for corrosion damage was established. Macroscopic detection, microscopic detection and internal damage detection were used to achieve quantitative characterization of corrosion damage and generate corresponding graded treatment results. Based on the classification and treatment results obtained from the four-level corrosion damage assessment system, graded and targeted repair processes are carried out on parts with different levels of corrosion damage. Surface passivation treatment, laser micro-melting repair or laser cladding repair are performed accordingly to restore the geometric dimensions and mechanical properties of the parts and improve corrosion resistance. After the graded and directional repair process is completed, a three-layer gradient composite anti-corrosion structure consisting of a substrate transition layer, a functional anti-corrosion layer and a surface sealing layer is constructed on the surface of the part according to the service conditions of the part. Continuous protection treatment is carried out on the repair area to achieve the integration of the repair area and the protection area. For parts treated with a three-layer gradient composite anti-corrosion structure, a special clean control process for chloride ions is implemented throughout the entire overhaul process. Chloride ion content control thresholds are set for the decomposition, cleaning, repair, assembly and commissioning processes, and step-by-step testing is carried out to achieve closed-loop management of the entire process. Using corrosion detection data, repair parameters, and protection parameters of parts treated by a chloride ion-specific clean control process, a marine environment corrosion-fatigue coupled remaining life prediction model was constructed. The remaining life of the parts was calculated and the performance was verified through bench tests. After completing the remaining service life prediction and performance verification, the corrosion detection data, repair process parameters, protective treatment parameters, clean control data and service life prediction results generated throughout the overhaul process are stored on the blockchain to establish a full-process airworthiness data traceability mechanism, so as to achieve data immutability and full node traceability.

[0007] The four-level corrosion damage assessment system includes Level I (slight corrosion), Level II (moderate corrosion), Level III (severe corrosion), and Level IV (scrap level). It targets three types of parts: cold-end moving parts, structural casing parts, and hot-end parts of the compressor. It adopts a three-level detection method consisting of macroscopic white light interferometry, microscopic scanning electron microscopy and energy dispersive spectroscopy analysis, and internal ultrasonic phased array detection to achieve quantitative characterization of corrosion damage.

[0008] The graded and targeted repair process includes: For parts with Class I slight corrosion, an integrated process of ultrasonic cleaning, composite passivation and nano-sealing is adopted; For Class II moderately corroded parts, a nanosecond pulsed laser micro-melting repair process is adopted, with the heat-affected zone not exceeding 50μm and the base deformation not exceeding 0.01mm; For Class III severely corroded parts, an ultra-high-speed laser cladding repair process is adopted, along with nano-reinforced corrosion-resistant cladding powder. The cladding layer forms a metallurgical bond with the substrate with a bonding strength of not less than 400 MPa. After cladding, laser remelting and homogenization treatment is carried out.

[0009] The three-layer gradient composite anti-corrosion structure includes: For the cold-end moving parts of the compressor, a three-layer structure consisting of a laser shock strengthening transition layer, a nano-composite ceramic anti-corrosion layer, and a hydrophobic sealing layer is adopted. After laser shock strengthening, the peak value of the residual compressive stress on the surface is not less than ≥-600MPa, and the influence depth is not less than ≥1mm. For magnesium alloy or aluminum alloy structural casings, a three-layer structure consisting of a micro-arc oxidation transition layer, an organic-inorganic composite anti-corrosion layer, and a weather-resistant topcoat layer is adopted, with a salt spray test life of not less than ≥3000h. For turbine hot-end components, a three-layer structure consisting of an MCrAlY bonding layer, a YSZ ceramic thermal barrier layer, and a heat corrosion resistant sealing layer is adopted, which improves the heat corrosion resistance performance by more than 60%.

[0010] The chloride ion-specific cleanroom control process includes five levels of control standards for the decomposition, cleaning, repair, assembly, and commissioning processes. During the cleaning process, the residual chloride ion concentration on the surface of parts and in internal cavities must not exceed [a certain value]. The amount of chloride ion deposition in the environment during the assembly process is not greater than [amount missing]. Each process is controlled according to a step-by-step inspection method.

[0011] The corrosion-fatigue coupled remaining life prediction model satisfies the following relationship: in, This represents the fatigue crack propagation rate. This represents the stress intensity factor amplitude. and For material fatigue performance parameters, For corrosion damage degree, The coefficient is the corrosion-fatigue coupling coefficient. The input parameters include the marine service load spectrum of the part throughout its entire life cycle, corrosion damage detection data, and material performance parameters. The output parameters are the remaining fatigue life and safe service life of the part.

[0012] The data from the entire overhaul process includes corrosion detection data, repair process parameters, protective treatment parameters, cleanliness control data, and life prediction results. The above data is stored on the blockchain using consortium blockchain technology, and the data retention period covers the entire life cycle of the engine. A multi-node authorized access mechanism is established to achieve data sharing and airworthiness review.

[0013] In the nanosecond pulsed laser micro-melting repair process, the average laser power is 50W-150W, the pulse width is 20ns-100ns, the scanning speed is 10mm / s-30mm / s, the spot diameter is 0.5mm-1.0mm, the overlap rate is 30%-50%, and the process is carried out in a high-purity inert gas protective environment.

[0014] The nanocomposite ceramic anti-corrosion layer is a multi-layered alternating structure coating, including a Ti layer, a TiN layer, and a TiAlN layer, with each layer having a thickness of [missing information]. The total thickness is The coating hardness is not less than 2000 HV, and the coating bonding strength is not less than 80 MPa.

[0015] The cleaning process employs a multi-stage cleaning method, including ultrasonic cleaning with deionized water, alkaline degreasing treatment, rinsing with deionized water, and hot air drying. The resistivity of the deionized water is no less than [value missing]. After cleaning, the residual chloride ion content was detected by ion chromatography.

[0016] The technical effects and advantages provided by the present invention in the above technical solution are as follows: This invention constructs a systematic corrosion protection system covering the entire engine overhaul process, integrating traditional decentralized single-point protection methods into a closed-loop control mode. It achieves synergistic optimization from corrosion source control to full-process management, effectively eliminating chloride ion residue and secondary corrosion risks. Through this system, the overhaul interval for engines in marine salt spray environments after overhaul has increased from approximately 60% of the parts being new to nearly 100% of the parts being new. Simultaneously, the corrosion-related fault return rate has significantly decreased from 42% to less than 3%, significantly improving the overall engine operational reliability and flight safety assurance capabilities.

[0017] This invention establishes a four-level corrosion damage grading and assessment system tailored to the characteristics of marine environments. It achieves precise quantification of corrosion damage through multi-scale detection methods and avoids errors arising from traditional experience-based judgments by combining grading treatment strategies. This system effectively solves the problem of excessive scrapping and unreasonable reuse, increasing the reuse rate of repairable parts from approximately 55% to over 90%, while significantly reducing spare parts consumption. The cost of spare parts for a single engine overhaul is reduced by more than 40%, demonstrating significant economic benefits and resource utilization advantages.

[0018] This invention achieves integrated design of repair and protection by constructing a graded directional repair process and a gradient composite protection system. This allows parts to restore their geometric dimensions while simultaneously improving the mechanical properties and corrosion resistance of the substrate. The substrate properties of the repaired parts can be restored to more than 95% of those of new parts, and the protection system achieves a service life of over 3000 hours in salt spray environments. Simultaneously, the hot-end components exhibit a more than 60% improvement in thermal corrosion resistance, meeting the stringent material performance requirements for long-term service in marine environments.

[0019] This invention establishes a specialized cleanroom control system for chloride ions throughout the entire process of disassembly, cleaning, repair, assembly, and commissioning. By setting tiered control thresholds and detection standards, closed-loop management is achieved between each process. Through this system, the residual chloride ion content of parts can be stably controlled within a specified range. Within this range, it effectively blocks the introduction of corrosive media during the overhaul process, fundamentally eliminating the conditions for secondary corrosion and significantly reducing the risk of early corrosion failure after the overhaul.

[0020] This invention establishes a full-process data storage and traceability system based on consortium blockchain technology. It stores key data such as testing data, process parameters, and verification results in an immutable manner, achieving full-process information transparency and traceability management. This system fully complies with the requirements for data authenticity and completeness in aviation airworthiness certification, enabling airworthiness reviews to be conducted efficiently based on real data, achieving a 100% first-time pass rate. Simultaneously, it provides data support for the quality management and continuous optimization of engines throughout their entire lifecycle.

[0021] The technical system constructed by this invention has good versatility and scalability. It is not only applicable to shipborne and maritime general aviation turboshaft engines, but can also be extended to turboprop engines, small turbofan engines, and other aviation power equipment serving in marine environments. Through modular technology combination and parameter adaptation, it can meet the overhaul requirements of different models and operating conditions, and also has the ability to extend to fields such as ship gas turbines, thus possessing high industry promotion value and application prospects. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0023] Figure 1 This is a flowchart of a method for systematic corrosion protection and life recovery of a turboshaft engine operating in a marine salt spray environment during overhaul, according to the present invention. Detailed Implementation

[0024] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that the description of this disclosure will be more complete and fully convey the concept of the exemplary embodiments to those skilled in the art.

[0025] This invention provides, for example Figure 1 The method for systemic corrosion protection and life recovery of a turboshaft engine operating in a marine salt spray environment during overhaul is shown below, with the specific steps as follows: To address the complex corrosion failure characteristics caused by the long-term coupling of high salinity, high humidity, and high chloride ion concentration in marine salt spray environments, a four-level corrosion damage grading and assessment system is constructed. This system provides a systematic, quantitative, and standardized analysis of corrosion damage, clarifying the quantitative indicators, detection methods, and treatment paths for different damage levels. This enables accurate identification and scientific grading of corrosion states, providing a reliable quantitative basis for decisions regarding part reuse, repair, or scrapping during engine overhauls. The assessment scope covers all engine system components. Based on the service environment, stress state, and corrosion sensitivity of different components, they are divided into three categories: cold-end moving components, including compressor rotor blades, stator blades, impellers, and intake casings, whose main corrosion forms are chloride ion-induced pitting and stress corrosion; structural casing components, including magnesium alloy or aluminum alloy intermediate casings, accessory casings, and gearbox housings, mainly facing crevice corrosion, general corrosion, and pitting; and hot-end components, including turbine blades, guide vanes, and combustion chamber flame tubes, which are exposed to the long-term coupling of high-temperature combustion gases and salt spray, making them prone to thermal corrosion and high-temperature oxidation corrosion. For the aforementioned different types of parts, a three-level detection system employing macroscopic, microscopic, and internal multi-scale collaborative methods is used to comprehensively identify and quantify corrosion damage. Macroscopic detection utilizes fluorescence penetrant detection and white light interferometry three-dimensional morphology scanning to measure surface corrosion pits, cracks, and wall thinning, with detection accuracy controlled within ±0.005 mm, achieving high-precision characterization of surface damage. Microscopic detection uses metallographic microscopy to observe changes in microstructure, combined with scanning electron microscopy and energy dispersive spectroscopy to identify intergranular corrosion, hydrogen embrittlement damage, and the composition of corrosion products, while also performing qualitative and quantitative analysis of chloride ion residues. Internal damage detection employs ultrasonic phased array and industrial CT technology to detect hidden defects such as corrosion cracks and interlayer damage within the matrix, achieving a detection resolution of 5 μm, thus enabling high-precision assessment of the material's internal structural integrity. This multi-scale, multi-method collaborative detection approach effectively avoids the limitations of single detection methods, achieving comprehensive corrosion damage identification from the surface to the interior.

[0026] Based on the above testing, a four-level corrosion damage classification standard and corresponding treatment plan were further established. Level I, slight corrosion, is characterized by a uniform surface corrosion depth not exceeding 0.02 mm, no pitting, no chloride ion components in the corrosion products, no intergranular corrosion or hydrogen embrittlement damage in the matrix, and a wall thickness reduction rate not exceeding 1%. The overall appearance is slight surface oxidation discoloration or loss of gloss, without localized corrosion defects, and the matrix mechanical properties remain stable. These parts can have their protective capabilities restored by ultrasonic cleaning to remove corrosion products, followed by surface passivation and sealing treatment, and can be directly reused. Level II, moderate corrosion, is characterized by localized pitting depth not exceeding 0.1 mm and a pitting density not exceeding 5 pits per minute. Meanwhile, the uniform corrosion depth does not exceed 0.05 mm, no intergranular corrosion or cracks appear inside the matrix, the wall thickness reduction rate does not exceed 5%, and the remaining wall thickness meets the design strength requirements. Typical characteristics are localized pitting corrosion and slight crevice corrosion. The mechanical properties of the matrix decrease by no more than 10%. Such parts can eliminate corrosion defects through directional repair methods such as laser micro-melting or micro-arc oxidation, and be reinforced with a gradient anti-corrosion coating. After passing performance verification, they can continue to be used. Class III severe corrosion is characterized by pitting depth between 0.1 mm and 0.3 mm, and pitting density not exceeding 10. Meanwhile, the uniform corrosion depth does not exceed 0.1 mm, local intergranular corrosion exists but the depth does not exceed 0.05 mm, no through cracks are formed, the wall thickness reduction rate does not exceed 10%, and the service requirements are still met after strength verification. Typical characteristics are dense pitting corrosion and deep crevice corrosion, and the mechanical properties of the matrix decrease by no more than 20%. Such parts need to be repaired by laser cladding or friction stir welding to restore the geometric dimensions and mechanical properties. The corrosion resistance is improved by integrating composite anti-corrosion coating with laser shock strengthening. After repair, full-size performance verification is required, and it can be reused only after passing the verification. Class IV scrap-level corrosion is characterized by pitting corrosion depth exceeding 0.3 mm or through corrosion cracks, wall thickness reduction rate exceeding 10% and the remaining wall thickness cannot meet the strength requirements. At the same time, there is deep intergranular corrosion, hydrogen embrittlement cracking or hot corrosion layer depth exceeding 0.1 mm, or the corrosion location is in a critical load-bearing area. It is difficult to guarantee the structural safety after repair. Such parts must be scrapped and replaced with new parts. The new parts need to undergo anti-corrosion pretreatment adapted to marine environment to avoid similar corrosion failures in subsequent service.

[0027] By establishing the aforementioned grading standards and treatment pathways, a closed-loop control system can be achieved from corrosion identification and quantitative assessment to treatment decision-making. This not only improves the objectivity and consistency of assessment results but also significantly reduces errors caused by human experience-based judgments, making parts handling during engine overhauls more scientific and rational. Simultaneously, the clear quantitative boundaries distinguishing different grades avoid over-scrapping or improper reuse, improving parts utilization and reducing overhaul costs while ensuring structural safety. Furthermore, the multi-scale detection system and grading standards form a mutually supportive relationship. Detection data directly serves grading determination, while grading results in turn guide subsequent repair and protection strategies, achieving synergistic unity between detection, assessment, and treatment. This constructs a systematic assessment mechanism applicable to the complex corrosion characteristics of marine salt spray environments.

[0028] For parts suffering from corrosion damage levels I-III, a graded and targeted repair process system is constructed based on a thorough identification of corrosion type, damage degree, and changes in matrix properties. Through differentiated process paths, this system simultaneously restores the part's geometric dimensions, optimizes the matrix microstructure, and enhances corrosion resistance, thus addressing the shortcomings of traditional repair processes that focus solely on dimensional restoration while neglecting material properties and environmental adaptability. This graded repair strategy uses corrosion damage levels as the main guideline, matching repair methods with damage mechanisms. This ensures the repair process is not only targeted but also considers the regulation of material microstructure and the improvement of surface protection capabilities, guaranteeing the reliability and stability of repaired parts for future service.

[0029] For Class I slightly corroded parts, including casings, blades, and other components without significant structural damage, an integrated ultrasonic cleaning-composite passivation-sealing process is employed for gentle yet efficient surface repair. First, ultrasonic cleaning removes corrosion products and contaminants adhering to the part surface. A mixture of anhydrous ethanol and deionized water is used as the cleaning medium, and cleaning is performed continuously at 40kHz for 10 minutes, utilizing cavitation to remove residual substances within micropores. High-purity nitrogen is then used for drying to prevent residual moisture from causing secondary corrosion. After cleaning, a composite passivation stage is initiated, with differentiated passivation methods for different substrates: titanium alloys undergo micro-arc oxidation to form a dense ceramic film with a thickness controlled between 5μm and 10μm, significantly improving surface hardness and corrosion resistance; aluminum alloys form a stable protective layer through rare earth conversion coating; and magnesium alloys are treated with a chromium-free, environmentally friendly passivation method to generate a protective film layer with a thickness of 3μm to 8μm, avoiding the environmental and health problems associated with traditional chromate processes. After the passivation film is formed, further nano-sealing is performed using nano-... The sealing agent fills the microporous structure of the film layer, through Curing for 30 minutes forms a tightly sealed layer, effectively blocking the chloride ion penetration path and thus significantly improving overall protective performance. This process restores and strengthens surface protection capabilities without altering the component's substrate structure, making it suitable for components with low damage levels and good structural integrity.

[0030] For Class II moderately corroded parts, mainly exhibiting localized pitting corrosion and slight crevice corrosion, a nanosecond pulsed laser micro-melting and directional repair process is employed to achieve precise repair of pitting defects and refinement of the substrate microstructure. Pre-treatment is required before repair. A fiber laser removes corrosion products and oxide layers from the corrosion pits, exposing the fresh metal substrate in the defect area. This is followed by ultrasonic cleaning with anhydrous ethanol and drying to ensure the cleanliness of the repair area. During the laser micro-melting and solidification process, a nanosecond pulsed fiber laser is selected. By controlling the average laser power within the range of 50W to 150W, the pulse width between 20ns and 100ns, the scanning speed between 10mm / s and 30mm / s, and the spot diameter between 0.5mm and 1.0mm, and setting an overlap rate of 30% to 50%, the energy input is precisely applied to the defect area, achieving localized melting and rapid solidification. High-purity argon gas is used for protection throughout the process, with the gas flow rate controlled within the range of 10L / min to 15L / min to prevent substrate oxidation at high temperatures. This process can form a dense, fused layer with a thickness of 0.1 mm to 0.2 mm on the surface of the part, while controlling the heat-affected zone to within 50 μm, significantly reducing the risk of microstructure coarsening caused by heat input, and controlling the matrix deformation to within 0.01 mm. The rapid solidification process is conducive to grain refinement, enabling the repaired area to obtain better mechanical properties and corrosion resistance, thereby achieving a balance between eliminating local defects and restoring performance.

[0031] For Class III severely corroded parts, typically load-bearing structural components such as casings, blades, and rotors, the corrosion is deep and accompanied by a certain degree of material loss. A combined process approach of ultra-high-speed laser cladding repair and microstructure homogenization is required. Before repair, a spatial geometric model of the corrosion defects is obtained using 3D blue light scanning technology. The defect area is digitally reconstructed, and the cladding path is planned. Simultaneously, the corrosion layer and fatigue damage layer are removed by machining to ensure that the subsequent cladding substrate is a complete and clean metal structure. Following this, ultrasonic cleaning with anhydrous ethanol and drying are performed. In the material preparation stage, a nano-reinforced cladding powder system is designed according to the corrosion resistance requirements of different substrates and marine environments: for TC4 titanium alloy, 88% to 92% matrix powder is used, with the addition of 3% to 6% nano-WC particles and 2% to 4% nano-... Rare earth particles and 0.5% to 2% nano-graphene are used to improve strength and corrosion resistance; for aluminum alloys, 90% to 95% Al-Si matrix powder is used with the addition of 2% to 5% nano-SiC particles and 1% to 3% nano-rare earth particles to enhance hardness and corrosion resistance; for nickel-based superalloys, 88% to 93% GH4169 matrix powder is used with the addition of 3% to 6% nano-TiC particles and 2% to 4% nano-rare earth particles. The powder contains 0.5% to 2% nano-graphene to enhance its high-temperature strength and antioxidant properties. The powder particle size is controlled within the range of 15μm to 53μm, with a sphericity of not less than 95%, and it is vacuum dried at 120℃ for 2 hours before use to remove adsorbed moisture.

[0032] During the cladding process, a five-axis linkage ultra-high-speed laser cladding system is employed. The laser power is controlled within the range of 800W to 1500W, the scanning speed between 40m / min and 80m / min, the powder feed rate between 15g / min and 25g / min, and the spot diameter between 0.6mm and 1.0mm. An overlap rate of 30% to 40% is set, and cladding deposition is completed under the protection of high-purity argon gas. The thickness of a single cladding layer is controlled between 0.1mm and 0.3mm, the heat-affected zone is controlled within 50μm, and the overall deformation of the substrate does not exceed 0.02mm. The cladding layer and the substrate form a metallurgical bond with a bonding strength of not less than 400MPa, thus achieving highly reliable structural restoration. After cladding, laser remelting is performed directly using the same laser system without transferring the workpiece. This further refines the grain size of the cladding layer, eliminates metallurgical defects such as porosity and cracks, and effectively reduces residual stress levels, thereby significantly improving the corrosion resistance and overall mechanical properties of the repaired area.

[0033] By establishing differentiated, targeted repair paths for Class I, II, and III corrosion damage, a multi-layered repair system is formed, encompassing surface treatment, local reconstruction, and structural rebuilding. This ensures that parts with varying degrees of damage can receive appropriate repair strategies, maximizing resource utilization while guaranteeing structural safety. Furthermore, each repair stage is collaboratively designed to control heat input, optimize microstructure, and enhance surface protection capabilities. This not only restores the original performance of the repaired area but also improves its corrosion resistance to a certain extent, making it more suitable for long-term service in marine salt spray environments.

[0034] For repaired parts, a three-layer gradient composite anti-corrosion protection system is constructed based on the different service conditions of various components in marine salt spray environments. This system consists of a substrate transition layer, a functional anti-corrosion layer, and a surface sealing layer. Through a progressively stronger structure from the inside out, the system achieves a synergistic effect of substrate performance transition, enhanced corrosion protection, and environmental isolation, forming an integrated structure between the repaired area and the protection system. This effectively solves the problems of insufficient adhesion between the coating and the substrate, easy peeling, and insufficient long-term service durability in traditional protection processes. This gradient system, through the matching design between different materials and processes, ensures that each layer maintains consistency in mechanical properties, thermal expansion characteristics, and interfacial bonding, avoiding interfacial failure. Simultaneously, the multi-layered structure provides multiple barriers against chloride ions, moisture, and high-temperature corrosive media.

[0035] 1. Cold-end moving parts protection system For cold-end moving parts (such as compressor blades and disks and other high-speed rotating parts), a gradient system of laser shock reinforced transition layer-nanocomposite ceramic anti-corrosion layer-hydrophobic sealing layer is constructed under the combined action of high flow rate salt spray erosion and high frequency alternating load.

[0036] 2. Structural casing protection system For structural casing components (such as magnesium alloy or aluminum alloy casings and gearbox housings), crevice corrosion and general corrosion are prone to occur in normal temperature, high humidity and high salt spray environments. A gradient system of micro-arc oxidation transition layer - organic-inorganic composite anti-corrosion layer - weather-resistant topcoat layer is constructed.

[0037] 3. Hot-end component protection system For hot-end components (such as turbine blades and combustion chamber components), which are prone to thermal corrosion and high-temperature oxidation in the combined environment of high-temperature gas and marine salt spray, a gradient system of MCrAlY bonding layer-YSZ ceramic thermal barrier layer-anti-thermal corrosion sealing layer is constructed.

[0038] By constructing differentiated three-layer gradient composite protection systems for cold-end moving parts, structural casings, and hot-end components, a comprehensive improvement in material strengthening, corrosion protection, and environmental adaptability is achieved. Stable interfaces are formed between each layer through optimized process parameters and material matching, ensuring the protection system maintains structural integrity and functional stability under complex loads and corrosive environments. Simultaneously, the gradient structural design allows stress to transition gradually between layers, reducing the risk of stress concentration at interfaces and thus improving overall service reliability. This system not only enhances the protection capabilities of the repaired area but also integrates repair and protection, enabling components to have a longer service life and higher safety and reliability when re-deployed to the marine environment.

[0039] To address the common issue of chloride ion residue and the resulting secondary corrosion risks associated with engines used in marine environments during overhauls, a comprehensive chloride ion-specific cleanliness control system has been established. This system identifies and controls pollution sources in each key process, blocking chloride ion introduction pathways at the source and suppressing corrosion risks throughout the entire process. Using quantitative indicators as its core and process control as its means, the system clarifies chloride ion residue thresholds and detection methods for each process, transforming cleanliness control from experience-based management to standardized and quantifiable management. Furthermore, a closed-loop mechanism is formed through inter-process control, ensuring that any step failing to meet standards prevents the next step from proceeding, thereby completely eliminating the hidden corrosion risks caused by control deficiencies in traditional processes.

[0040] For the five core processes of disassembly, cleaning, repair, assembly and commissioning, a five-level chloride ion control standard was established to form a control system that tightens step by step from low to high. By implementing the above five-level standards for step-by-step control, a transition from coarse to fine control is achieved. The principle of "if the previous process is unqualified, the next process will not accept it" is adopted to build a closed-loop management system for the entire process.

[0041] Detailed control measures for each process 1. Decomposition process: To prevent external salt spray crystals from penetrating the interior of the parts, a high-pressure rinse with deionized water is required before disassembly to thoroughly remove salt and contaminants adhering to the outer surface. During disassembly, all oil ports and cavity openings are immediately sealed using specialized dust plugs to prevent external contaminants from entering, and covered transport boxes are used to avoid cross-contamination between different parts. Chloride ion residue testing is immediately conducted after disassembly; only parts meeting the L1 level control standard are allowed to proceed to the next process, thus ensuring that subsequent cleaning steps are carried out under controlled contamination levels.

[0042] 2. Cleaning process: The parts undergo a four-stage cleaning process: ultrasonic cleaning with deionized water, alkaline degreasing, rinsing with deionized water, and hot air drying. Ultrasonic cleaning: Utilizes the cavitation effect to remove attached contaminants.

[0043] Alkaline degreasing: Used to remove oil stains and organic residues.

[0044] Rinsing process: Use a rinsing agent with a resistivity of not less than High-purity deionized water is used to avoid introducing new ion contamination.

[0045] Hot air drying: eliminates residual moisture.

[0046] After cleaning, the residual chloride ions on the parts are detected by ion chromatography. Once the L2 standard is met, the parts are immediately individually sealed in vacuum bags and stored in a constant temperature and humidity clean cabinet to prevent moisture and salt from adhering to them again.

[0047] 3. Repair process: To avoid introducing new sources of contamination during the repair process, all non-repair areas of the parts must be fully encased and protected before repair to prevent particles or liquids generated during processing from entering the internal structure. Simultaneously, the use of coolants or cleaning agents containing chloride ions is strictly prohibited, ensuring the entire repair environment remains low-chlorine. After repair, a second cleaning process and chloride ion testing are required. Only parts meeting the L3 standard can proceed to subsequent protection and assembly stages, thus guaranteeing that the repair process will not become a source of contamination.

[0048] 4. Assembly process: By establishing a dedicated clean assembly room for marine-environment engines, environmental level control can be achieved. Environmental parameters: Cleanliness reaches ISO 7 level, temperature is controlled at... to Between, relative humidity is controlled at to between.

[0049] Monitoring mechanism: The amount of chloride ion deposition in the environment is continuously monitored 24 hours a day through an online monitoring system to ensure that it does not exceed the limit. .

[0050] Material control: All tools, fixtures and auxiliary materials entering the assembly room must be cleaned and tested for chloride ions, and can only be used after they are confirmed to meet the standards.

[0051] Operating procedures: Parts should only be unsealed before assembly. When assembly is interrupted, dust covers should be used for full coverage to prevent airborne pollutants from settling.

[0052] All openings are immediately sealed after assembly, and the equipment is stored using vacuum sealing to avoid the risk of contamination from subsequent environmental exposure.

[0053] 5. Trial run procedure: Chloride ion testing is performed on lubricating oil and fuel to ensure they meet L5 level control standards. The test bench intake system is equipped with a salt spray filter with a filtration efficiency of no less than [percentage missing]. This effectively prevents external salt spray from entering the engine. After the test run, the lubrication system and intake passage are inspected again to confirm the absence of chloride ion residue. The engine is then sealed with oil and stored using vacuum moisture-proof packaging suitable for marine environments to ensure it is not affected by the environment during transportation and storage.

[0054] The establishment of the aforementioned end-to-end chloride ion cleanliness control system enables pollution control and risk isolation throughout the entire process, from decomposition, cleaning, repair, assembly to test runs. Each process is closely linked through quantitative indicators and testing methods, forming a complete closed loop. This system not only effectively reduces chloride ion residue levels but also fundamentally eliminates the conditions for secondary corrosion, giving the engine higher environmental adaptability and long-term service reliability after overhaul. It also provides a stable and reliable foundation for subsequent performance evaluation and lifespan prediction.

[0055] To address the significant impact of corrosion damage on the fatigue performance of engine components in marine environments, a marine-specific residual fatigue life prediction model was established. This model enables a quantitative description and accurate assessment of component life status, providing a scientific basis for decisions regarding component reuse, repair, and replacement during overhauls. The model focuses on the coupling effect of corrosion damage and fatigue crack propagation behavior. By introducing corrosion influencing factors, it extends traditional fatigue life analysis methods to the complex service conditions of marine salt spray environments, making life assessment results more consistent with actual operating conditions. Corrosion not only alters the surface state of materials but also induces microstructural deterioration and stress concentration effects, thereby accelerating fatigue crack initiation and propagation. Therefore, in the life prediction process, corrosion factors and fatigue behavior must be modeled in a unified manner to improve the accuracy and engineering applicability of the prediction results.

[0056] Regarding model construction, a corrosion-fatigue coupled life prediction model is established based on the theories of continuous damage mechanics and fracture mechanics, and its expression is as follows: This expression introduces a corrosion damage effect term based on the classic Paris formula, by multiplying by... To correct the corrosion acceleration effect, among which, Indicates the fatigue crack propagation rate. Indicates the magnitude of the stress intensity factor. and These are fatigue performance parameters of materials, reflecting the crack propagation characteristics of materials under non-corrosion conditions; The degree of corrosion damage is indicated by quantitative calculations of pitting depth, intergranular corrosion depth, and residual chloride ion content. This parameter comprehensively reflects the extent to which corrosion weakens the material's properties. The corrosion-fatigue coupling coefficient is determined through accelerated corrosion-fatigue tests in a marine environment. Different values ​​are assigned to different material types and service conditions to ensure the model is applicable to various material systems and operating conditions. By introducing corrosion damage degree and coupling coefficient, the amplification effect of corrosion on crack propagation rate can be effectively described, enabling the model to reflect the complex mechanism of mutual promotion between corrosion and fatigue in actual marine environments.

[0057] During model application, input parameters include the marine environmental service load spectrum of the component throughout its entire service life, corrosion damage detection data, material mechanical property attenuation coefficients, and corrosion resistance performance parameters of the protection system. The load spectrum reflects the stress cycle characteristics of the component during actual service and is the fundamental data for fatigue analysis; the corrosion damage detection data comes from previous detection results, including information on pitting corrosion, intergranular corrosion, and chloride ion residue, providing... The calculations provide the basis for the model; the material mechanical property attenuation coefficient describes the impact of corrosion and repair processes on material properties; and the corrosion resistance parameters of the protection system reflect the inhibitory effect of protective measures on the corrosion rate. Through comprehensive analysis of the above multi-source data, the model outputs the remaining fatigue life of components, the safe service life after overhaul, and the critical corrosion damage threshold, thus providing a quantitative basis for subsequent maintenance strategy formulation. This model can not only assess the remaining life under the current condition but also predict the life change trend under different service conditions and maintenance strategies, possessing strong engineering guidance significance.

[0058] In terms of life verification and compliance assessment, a combination of testing and simulation is used to verify and correct the model prediction results. In the accelerated performance verification phase, furnace-mounted test pieces and simulated parts are extracted from the same batch of repaired components for neutral salt spray accelerated corrosion tests and high- and low-cycle fatigue tests. By simulating corrosion and load effects in actual service through accelerated environmental testing, the corrosion resistance and fatigue strength of the materials are comprehensively evaluated, thereby verifying the rationality of the model prediction results and confirming whether the remaining life meets the overhaul interval requirements. In the full-condition bench verification phase, after the engine assembly is completed, a marine environment simulation bench test is conducted. A quantitative amount of salt spray is introduced into the intake system to simulate the real marine service environment. Simultaneously, key parameters such as vibration, temperature, and performance are collected to monitor and analyze the engine's operating status under complex conditions, verifying its corrosion resistance reliability and performance stability. This process not only verifies the performance of individual components but also assesses the reliability of the coordinated operation of various components at the overall engine level.

[0059] In the life compliance assessment phase, model predictions are comprehensively compared and analyzed with accelerated and bench test data to confirm the consistency between predicted life and actual performance. Based on this, the safe service life of the engine after overhaul is determined, and quantitative recommendations for reuse, periodic inspection, or replacement of different parts are proposed, forming a complete life assessment report. This report includes not only remaining life calculation results but also experimental verification data and analysis conclusions, serving as an important basis for airworthiness certification. By establishing an assessment system combining model prediction and experimental verification, life assessment shifts from experience-based judgment to data-driven approaches, improving the scientific rigor and reliability of the assessment results. Simultaneously, by determining the critical corrosion damage threshold, early warning information can be provided for subsequent operational monitoring, enabling timely identification and maintenance measures before parts approach failure, thereby effectively improving the overall operational safety of the engine.

[0060] By constructing a corrosion-fatigue coupled life prediction model and combining it with multi-level verification methods, a closed-loop control system is achieved from damage identification and life prediction to verification and evaluation, making the life management of engine components in marine environments more precise and controllable. Under the combined effects of complex corrosive environments and alternating loads, this method can comprehensively reflect the evolution of material properties, providing reliable support for overhaul decisions and further improving the long-term service capability and safety assurance level of engines in marine environments.

[0061] To address the stringent requirements for data authenticity, completeness, and traceability during the airworthiness certification process for civil and military aviation equipment, a corrosion protection data storage and traceability system covering the entire engine overhaul process is constructed by introducing consortium blockchain technology. This system provides unified management and secure storage of key data generated at each stage, achieving data immutability, end-to-end traceability, and multi-party collaborative supervision. Based on a distributed ledger, the system uses inter-node data synchronization and consensus mechanisms to structurally record information related to testing, repair, protection, and verification during the overhaul process. This ensures that each operation has a verifiable source, thus meeting the mandatory requirements for data authenticity and completeness during airworthiness certification. Furthermore, by linking data in a chain, the system achieves seamless data flow from single-process data to full lifecycle data, transforming overhaul quality control from traditional paper-based or single-point recording methods to a digital, networked, and traceable management model.

[0062] Regarding the on-chain storage of data throughout the entire process, an independent electronic file for marine environmental overhaul corrosion protection is established for each engine. Consortium blockchain technology is used to process the relevant data on the blockchain, ensuring that the data is tamper-proof once entered and that its retention period covers the entire engine lifecycle. The electronic file contains multiple key data dimensions: including incoming corrosion damage assessment data, test reports, and graded treatment plans, which record the initial state of parts and the basis for treatment; including full-process parameters of part repair and protection processes, as well as information on corresponding operators and inspectors, enabling dual traceability of the process and responsible parties; including full-process chloride ion cleanliness control test data and environmental monitoring data, reflecting the cleanliness control level of each process; including remaining service life prediction reports, performance verification test data, and bench test data, proving that the repaired parts and the overall engine performance meet usage requirements; and also including metrological calibration certificates for testing equipment, operator qualification certificates, and airworthiness compliance declarations, ensuring the legality and standardization of the testing and operation processes. Through the unified on-chain storage of the above multi-dimensional data, various types of information form a linked data chain, allowing traceability to the original record at any node, thereby achieving transparent management throughout the entire process.

[0063] Regarding multi-node authorized access and airworthiness control, a consortium blockchain multi-node authorization mechanism is constructed, setting overhaul units, airlines, civil aviation airworthiness departments, and manufacturing units as core nodes. Different data access permissions are assigned according to the responsibilities of each participant, achieving a balance between data sharing and secure isolation. Overhaul units are mainly responsible for data entry and maintenance, airlines focus on querying operational status and maintenance records, airworthiness departments are responsible for review and supervision, and manufacturing units are used for product improvement and quality traceability. Through hierarchical access control, data security is ensured while enabling multi-party collaborative supervision. During the airworthiness review process, the "Engine Overhaul Corrosion Protection Report," "Parts Repair and Performance Verification Report," and "Declaration of Airworthiness Compliance" can be automatically generated based on the on-chain stored data. All report content originates from on-chain data, possessing traceability and verifiability characteristics, thereby significantly improving review efficiency and reducing the risk of human intervention, ensuring that airworthiness reviews are passed on the first attempt.

[0064] Regarding the construction of a closed-loop data system throughout the entire engine lifecycle, corrosion data generated during engine field service is continuously fed back to the on-chain system, enabling the connection between operational and overhaul data. This ensures that data is no longer limited to a single overhaul cycle but spans the entire service life. Corrosion types, development trends, and environmental parameters detected in the field can be fed back as input data to the overhaul process system to optimize repair strategies, protection schemes, and cleanliness control standards, thus forming a continuously iterative technical optimization mechanism. Through this closed-loop feedback model, the targeting and effectiveness of corrosion protection processes can be gradually improved, enabling the overhaul technology system to possess dynamic optimization capabilities.

[0065] By establishing a consortium blockchain-based end-to-end data storage and traceability system, the entire chain of management—from data collection, storage, and sharing to application—is achieved, ensuring that every critical operation during engine overhaul has complete data support and a clear path for accountability. This not only meets the airworthiness certification requirements for data integrity and authenticity but also provides a reliable data foundation for subsequent quality analysis, fault tracing, and process optimization. This system not only improves the standardization of the overhaul process but also significantly enhances the safety assurance capabilities of aviation equipment in complex marine environments, providing crucial support for achieving high reliability and long service life.

[0066] Example: This embodiment focuses on a 1000kW turboshaft engine used in a domestic shipborne helicopter. This engine has been operating for a long time in the high-salt spray, high-humidity, and high-chloride-ion environment of the South China Sea, accumulating 1200 hours of service. During the initial inspection before the overhaul, various key components showed varying degrees of corrosion damage. The compressor titanium alloy blades exhibited moderate pitting corrosion, the aluminum alloy accessory housing showed significant crevice corrosion accompanied by some wall thinning, and the turbine guide vanes showed slight hot corrosion. Traditional overhaul methods would require replacing all 12 compressor blades and the entire accessory housing, significantly increasing spare parts costs. Furthermore, the overhaul interval in the marine environment would only be approximately 700 hours, insufficient for long-term service. Therefore, a systematic corrosion protection and life recovery technology approach was introduced to perform a full-process overhaul of this engine.

[0067] During the incoming inspection phase, the engine undergoes a comprehensive disassembly and is categorized into three types of components based on their service characteristics: Category A cold-end moving parts, Category B structural casing parts, and Category C hot-end parts. Based on this, a comprehensive inspection is conducted using macroscopic, microscopic, and internal multi-scale testing methods. This includes acquiring surface corrosion morphology characteristics through white light interferometry, identifying corrosion product composition and chloride ion residue using scanning electron microscopy combined with energy dispersive spectroscopy, and detecting internal defects in the substrate using ultrasonic phased array technology. Based on the inspection results, each type of component is graded and evaluated: the pitting depth of the 12 first-stage moving blades of the compressor is 0.08 mm, and the pitting density is 3. No intergranular corrosion or internal cracks were found, classifying it as Level II moderate corrosion. The aluminum alloy accessory casing showed 0.25mm deep crevice corrosion at the mounting edge, with a wall thickness reduction rate of 8%, but the remaining wall thickness still met strength requirements, classifying it as Level III severe corrosion. The turbine guide vane had a corrosion layer depth of 0.02mm, with no cracks or pitting found, classifying it as Level I slight corrosion. All other parts were in a Level I slight corrosion state, and no Level IV scrapping conditions were observed. Based on the above assessment results, a graded treatment plan was formulated, and the test data and assessment report were uniformly entered into an electronic archiving system for record-keeping.

[0068] During the repair phase, differentiated repair approaches were implemented for parts with different corrosion levels. Level I corrosion parts, including turbine guide vanes and other slightly corroded components, underwent ultrasonic cleaning, composite passivation, and nano-sealing processes. Specifically, the titanium alloy guide vanes underwent micro-arc oxidation to form a dense ceramic film approximately 8 μm thick, followed by nano-sealing. After sealing, the residual chloride ion content was controlled below 5 μg / cm², meeting the cleanliness control requirements. The compressor blades with Class II corrosion were repaired using a nanosecond pulsed laser micro-melting process. The process was completed under conditions of an average laser power of 100W, a pulse width of 50ns, a scanning speed of 20mm / s, a spot diameter of 0.8mm, and an overlap rate of 40%. Complete elimination of pitting defects was achieved in a high-purity argon protective environment, forming a dense melting layer approximately 0.15mm thick. The heat-affected zone was controlled below 42μm, and the deformation was less than 0.01mm. After repair, the mechanical properties of the substrate were restored to 98% of those of a new part. The aluminum alloy accessory housing with Class III corrosion was repaired using ultra-high-speed laser cladding. A nano-reinforced powder system based on Al-Si was used, and cladding was completed under conditions of 1200W laser power, 60m / min scanning speed, and 20g / min powder feed. Subsequent laser remelting was used to homogenize the microstructure, ultimately forming a metallurgical bond with the substrate with a strength of no less than 400MPa. Simultaneously, the heat-affected zone was controlled to be no more than 50μm, and the deformation was less than 0.02mm. All repaired parts underwent further cleaning and chloride ion testing. Only after meeting the specified standards did they proceed to the subsequent protective treatment stage.

[0069] During the protection system construction phase, targeted gradient protection schemes are implemented based on the service environment characteristics of different components. The compressor blades employ a three-layer structure consisting of laser shock peening, a nano-composite ceramic coating, and a hydrophobic sealing layer, utilizing energy density... A reinforced layer with a residual compressive stress peak of -650MPa and an influence depth of 1.2mm is formed through a 15ns pulse width and two impact treatments. A 15μm thick multilayer ceramic coating is then formed via magnetron sputtering, followed by a 2μm thick hydrophobic sealing layer with a water contact angle of 128° via vapor deposition. The aluminum alloy accessory housing employs a combination of micro-arc oxidation, a composite anti-corrosion coating, and a weather-resistant topcoat. The micro-arc oxidation layer is 25μm thick, the composite coating is 40μm thick, and the topcoat is 25μm thick, achieving an overall salt spray test life exceeding 3000 hours. The turbine guide vanes utilize an MCrAlY bonding layer, a YSZ ceramic layer, and a sealing layer structure. A high-performance thermal barrier system is formed using HVOF and EB-PVD technologies. The sealing layer is approximately 8μm thick, improving hot corrosion resistance by about 65%. After protection, the corrosion resistance and bonding strength of each component are tested, and they are uniformly packaged and stored.

[0070] Throughout the overhaul, strict adherence to chloride ion cleanliness control requirements was enforced, with full-process monitoring of decomposition, cleaning, repair, and assembly to ensure compliance with corresponding control standards at each stage. During the assembly phase, an ISO 7 clean environment was employed, with temperature controlled at [temperature range missing]. Humidity is controlled at 45%, and chloride ion deposition is continuously monitored to ensure it does not exceed [a certain value]. During the test run, chlorine-free lubricating oil and fuel were used, and a high-efficiency filtration system was used to prevent salt spray from entering the engine. After the test run, the chloride ion content of the lubricating oil was tested and found to be no more than 0.5 mg / L. All test data and environmental parameters were recorded and managed in an electronic filing system.

[0071] In terms of life assessment and verification, the remaining engine life was calculated using a corrosion-fatigue coupling model. After inputting the actual service load spectrum and test data, the remaining life was found to be no less than 1500 hours, meeting the design requirement of 1200 hours. Simultaneously, the repair effect was verified through salt spray accelerated testing and fatigue testing. The results showed that the fatigue strength recovered to 96% of that of a new part, and the corrosion resistance improved by more than 60%. During the full-engine bench test, all performance parameters met the design requirements, and no abnormal vibrations or malfunctions occurred.

[0072] During the data management and delivery phase, all data from the overhaul process is stored and authenticated via a consortium blockchain, ensuring data immutability and full traceability, and automatically generating relevant airworthiness documents. Finally, after oil sealing and vacuum moisture-proof sealing, the data is delivered to the user unit, and data access permissions are granted to support subsequent operation and management.

[0073] The results show that under this technical approach, no engine parts were scrapped, the reuse rate reached 100%, and spare parts costs were saved by about 180,000 yuan compared with the traditional method. At the same time, the service life after the overhaul was restored to 1,200 hours, the corrosion-related failure repair rate was reduced to less than 2%, and the overall performance and airworthiness requirements fully met the usage requirements.

[0074] Modified embodiment: This embodiment focuses on another typical marine environment service scenario: a 600kW turboshaft engine used in a domestic maritime search and rescue helicopter. This type of engine operates long-term in near-shore areas, characterized by a persistent combination of high salt spray and high humidity, coupled with the inhalation of high salt spray and particulate erosion effects from low-altitude flight. After 1000 hours of cumulative service, the engine entered its overhaul phase. Inspection revealed significant severe corrosion damage to the magnesium alloy gearbox housing, characterized by a deep corrosion layer and reduced local structural integrity; the compressor blades exhibited a combination of minor erosion and pitting corrosion. To address these corrosion characteristics, adaptations were made to the existing technology system to meet the specific service requirements of the near-shore environment.

[0075] To address the Class III corrosion issue in magnesium alloy gearbox housings, an environmentally friendly chromium-free passivation pretreatment process was introduced during the repair procedure. This process forms a stable surface conversion film, providing a good interface foundation for subsequent cladding, while avoiding the environmental and safety issues associated with traditional chromium-containing processes. In the subsequent repair stage, ultra-high-speed laser cladding technology was employed, and a specialized cladding powder system was developed specifically for the characteristics of magnesium alloys. By controlling the heat input and protective atmosphere during the cladding process, burn-off or oxidation of the magnesium alloy under high-temperature conditions was prevented, thus ensuring the integrity of the microstructure and the restoration of mechanical properties in the repaired area. This adjustment enables reliable repair of magnesium alloy structural components even in complex corrosive environments, avoiding the high costs associated with complete replacement.

[0076] To address the increased demands on structural component protection in the high-humidity nearshore environment, the protective layer of the structural casing components was functionally enhanced based on the existing gradient protection system. By introducing anti-mildew additives into the weather-resistant topcoat, the coating acquires resistance to microbial erosion, achieving a mildew resistance level of 0. In high-humidity environments, microbial attachment and reproduction often accelerate the corrosion process. This improvement effectively inhibits mold growth and, in conjunction with salt spray and moisture-proof properties, ensures the structural components remain stable during long-term service, meeting the NBC (nuclear, biological, chemical) protection requirements of the marine environment.

[0077] To address the erosion problem of compressor blades caused by high salt spray and particulate inhalation under near-shore low-altitude flight conditions, an anti-erosion phase design was introduced into the blade protection system. This was achieved by adding anti-erosion components to the nanocomposite ceramic protective layer, enhancing the coating's resistance to sand and dust particles and salt spray erosion, thereby reducing the rate of buffer erosion and wear. This optimization allows the coating to maintain its original corrosion resistance while also possessing excellent impact and wear resistance, meeting the long-term operational requirements of the complex aerodynamic environment in near-shore areas.

[0078] Apart from the targeted adjustments mentioned above, the remaining process flows, including corrosion damage classification and assessment, graded and targeted repair, gradient protection construction, chloride ion cleanroom control, life prediction, and data storage, remain consistent with the preferred implementation method, thereby ensuring the integrity and stability of the overall technical route. Through adjustments to local parameters and processes, adaptability to different environmental conditions is achieved, demonstrating strong engineering adaptability.

[0079] The implementation results show that, under this modified implementation method, the magnesium alloy gearbox housing was successfully repaired and reused, avoiding the resource waste of a complete replacement and saving approximately 120,000 yuan in spare parts costs. Simultaneously, after the overhaul, the engine's service life in the near-shore environment was restored to the level of a new part, with its anti-mildew, moisture-proof, and salt spray resistance all meeting design requirements, and operational stability significantly improved. During the airworthiness review process, due to the complete and traceable data throughout the entire process and the sufficient relevant testing and verification results, it successfully passed the review on the first attempt, verifying the applicability and reliability of this technical approach under different marine environmental conditions.

[0080] The comparative example used the same engine model and parts from the same batch as the preferred embodiment, and was treated according to the standard single-point repair plus end-of-line protection process used in the domestic overhaul industry. Upon arrival at the factory, parts were evaluated solely through visual inspection and fluorescent penetrant testing, directly identifying 12 compressor blades and the accessory casing as exceeding standards and scrapping them entirely, resulting in spare parts costs of 220,000 yuan. The remaining parts were manually washed with kerosene without in-depth testing before entering the assembly stage; no chloride ion residue testing was performed throughout the process, posing a significant safety hazard. Regarding protective treatment, newly replaced parts only underwent conventional anodizing and painting processes, without establishing a tiered protection system specific to the marine environment. During assembly, a standard workshop environment was used, without specific chloride ion control; cleanliness standards were based on inland environmental requirements, without considering the unique characteristics of the marine environment. After the entire engine was assembled, it was only put into use after verifying its performance through routine bench testing.

[0081] The results showed that after approximately 650 hours of service in the marine environment, the engine developed multiple corrosion-related failures, including recurrence of pitting corrosion on the compressor blades, crevice corrosion at the accessory housing mounting edge, and clogging of the lubricating oil nozzles. Disassembly and inspection upon return to the factory revealed a large amount of residual chloride ions in the internal cavities of the parts, resulting in typical secondary corrosion. The repair rate for corrosion-related failures reached 100%. Furthermore, due to the frequent occurrence of failures, the overhaul cycle was extended by approximately 10 days compared to the preferred implementation method, and the overall cost increased by approximately 65%. More seriously, the structural safety hazards caused by corrosion damage failed to meet the civil aviation airworthiness certification requirements, posing a significant risk.

[0082] The comparison shows that adopting a systematic corrosion protection and life recovery technology approach has significant advantages in reducing costs, improving reliability, and meeting seaworthiness requirements. In contrast, traditional processes, due to the lack of systematic control and environmental adaptability design, are difficult to meet the long-term service requirements in marine environments.

[0083] This invention constructs a systematic corrosion protection system covering the entire engine overhaul process, integrating traditional decentralized single-point protection methods into a closed-loop control mode. It achieves synergistic optimization from corrosion source control to full-process management, effectively eliminating chloride ion residue and secondary corrosion risks. Through this system, the overhaul interval for engines in marine salt spray environments after overhaul has increased from approximately 60% of the parts being new to nearly 100% of the parts being new. Simultaneously, the corrosion-related fault return rate has significantly decreased from 42% to less than 3%, significantly improving the overall engine operational reliability and flight safety assurance capabilities.

[0084] This invention establishes a four-level corrosion damage grading and assessment system tailored to the characteristics of marine environments. It achieves precise quantification of corrosion damage through multi-scale detection methods and avoids errors arising from traditional experience-based judgments by combining grading treatment strategies. This system effectively solves the problem of excessive scrapping and unreasonable reuse, increasing the reuse rate of repairable parts from approximately 55% to over 90%, while significantly reducing spare parts consumption. The cost of spare parts for a single engine overhaul is reduced by more than 40%, demonstrating significant economic benefits and resource utilization advantages.

[0085] This invention achieves integrated design of repair and protection by constructing a graded directional repair process and a gradient composite protection system. This allows parts to restore their geometric dimensions while simultaneously improving the mechanical properties and corrosion resistance of the substrate. The substrate properties of the repaired parts can be restored to more than 95% of those of new parts, and the protection system achieves a service life of over 3000 hours in salt spray environments. Simultaneously, the hot-end components exhibit a more than 60% improvement in thermal corrosion resistance, meeting the stringent material performance requirements for long-term service in marine environments.

[0086] This invention establishes a specialized cleanroom control system for chloride ions throughout the entire process of disassembly, cleaning, repair, assembly, and commissioning. By setting tiered control thresholds and detection standards, closed-loop management is achieved between each process. Through this system, the residual chloride ion content of parts can be stably controlled within a specified range. Within this range, it effectively blocks the introduction of corrosive media during the overhaul process, fundamentally eliminating the conditions for secondary corrosion and significantly reducing the risk of early corrosion failure after the overhaul.

[0087] This invention establishes a full-process data storage and traceability system based on consortium blockchain technology. It stores key data such as testing data, process parameters, and verification results in an immutable manner, achieving full-process information transparency and traceability management. This system fully complies with the requirements for data authenticity and completeness in aviation airworthiness certification, enabling airworthiness reviews to be conducted efficiently based on real data, achieving a 100% first-time pass rate. Simultaneously, it provides data support for the quality management and continuous optimization of engines throughout their entire lifecycle.

[0088] The technical system constructed by this invention has good versatility and scalability. It is not only applicable to shipborne and maritime general aviation turboshaft engines, but can also be extended to turboprop engines, small turbofan engines, and other aviation power equipment serving in marine environments. Through modular technology combination and parameter adaptation, it can meet the overhaul requirements of different models and operating conditions, and also has the ability to extend to fields such as ship gas turbines, thus possessing high industry promotion value and application prospects.

[0089] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for systemic corrosion protection and life recovery during the overhaul of a turboshaft engine operating in a marine salt spray environment, characterized in that, Includes the following steps: Corrosion damage detection was carried out on turboshaft engines operating in marine salt spray environment. A four-level classification assessment system for corrosion damage was established. Macroscopic detection, microscopic detection and internal damage detection were used to achieve quantitative characterization of corrosion damage and generate corresponding graded treatment results. Based on the classification and treatment results obtained from the four-level corrosion damage assessment system, graded and targeted repair processes are carried out on parts with different levels of corrosion damage. Surface passivation treatment, laser micro-melting repair or laser cladding repair are performed accordingly to restore the geometric dimensions and mechanical properties of the parts and improve corrosion resistance. After the graded and directional repair process is completed, a three-layer gradient composite anti-corrosion structure consisting of a substrate transition layer, a functional anti-corrosion layer and a surface sealing layer is constructed on the surface of the part according to the service conditions of the part. Continuous protection treatment is carried out on the repair area to achieve the integration of the repair area and the protection area. For parts treated with a three-layer gradient composite anti-corrosion structure, a special clean control process for chloride ions is implemented throughout the entire overhaul process. Chloride ion content control thresholds are set for the decomposition, cleaning, repair, assembly and commissioning processes, and step-by-step testing is carried out to achieve closed-loop management of the entire process. Using corrosion detection data, repair parameters, and protection parameters of parts treated by a chloride ion-specific clean control process, a marine environment corrosion-fatigue coupled remaining life prediction model was constructed. The remaining life of the parts was calculated and the performance was verified through bench tests. After completing the remaining service life prediction and performance verification, the corrosion detection data, repair process parameters, protection treatment parameters, clean control data and service life prediction results generated throughout the overhaul process are stored on the blockchain to establish a full-process airworthiness data traceability mechanism, so as to achieve data immutability and full node traceability.

2. The method for systemic corrosion protection and life recovery of a turboshaft engine operating in a marine salt spray environment during overhaul, as described in claim 1, is characterized in that... The four-level corrosion damage assessment system includes Level I (slight corrosion), Level II (moderate corrosion), Level III (severe corrosion), and Level IV (scrap level). It targets three types of parts: cold-end moving parts, structural casing parts, and hot-end parts of the compressor. It adopts a three-level detection method consisting of macroscopic white light interferometry, microscopic scanning electron microscopy and energy dispersive spectroscopy analysis, and internal ultrasonic phased array detection to achieve quantitative characterization of corrosion damage.

3. The method for systemic corrosion protection and life recovery of a turboshaft engine operating in a marine salt spray environment during overhaul, as described in claim 2, is characterized in that... The graded and targeted repair process includes: For parts with Class I slight corrosion, an integrated process of ultrasonic cleaning, composite passivation and nano-sealing is adopted; For Class II moderately corroded parts, a nanosecond pulsed laser micro-melting repair process is adopted, with the heat-affected zone not exceeding 50μm and the base deformation not exceeding 0.01mm; For Class III severely corroded parts, an ultra-high-speed laser cladding repair process is adopted, along with nano-reinforced corrosion-resistant cladding powder. The cladding layer forms a metallurgical bond with the substrate with a bonding strength of not less than 400 MPa. After cladding, laser remelting and homogenization treatment is carried out.

4. The method for systemic corrosion protection and life recovery of a turboshaft engine operating in a marine salt spray environment during overhaul, as described in claim 1, is characterized in that... The three-layer gradient composite anti-corrosion structure includes: For the cold-end moving parts of the compressor, a three-layer structure consisting of a laser shock strengthening transition layer, a nano-composite ceramic anti-corrosion layer, and a hydrophobic sealing layer is adopted. After laser shock strengthening, the peak value of the residual compressive stress on the surface is not less than ≥-600MPa, and the influence depth is not less than ≥1mm. For magnesium alloy or aluminum alloy structural casings, a three-layer structure consisting of a micro-arc oxidation transition layer, an organic-inorganic composite anti-corrosion layer, and a weather-resistant topcoat layer is adopted, with a salt spray test life of not less than ≥3000h. For turbine hot-end components, a three-layer structure consisting of an MCrAlY bonding layer, a YSZ ceramic thermal barrier layer, and a heat corrosion resistant sealing layer is adopted, which improves the heat corrosion resistance performance by more than 60%.

5. The method for systemic corrosion protection and life recovery of a turboshaft engine operating in a marine salt spray environment during overhaul, as described in claim 1, is characterized in that... The chloride ion-specific cleanroom control process includes five levels of control standards for the decomposition, cleaning, repair, assembly, and commissioning processes. During the cleaning process, the residual chloride ion concentration on the surface of parts and in internal cavities must not exceed [a certain value]. The amount of chloride ion deposition in the environment during the assembly process is not greater than [amount missing]. Each process is controlled according to a step-by-step inspection method.

6. The method for systemic corrosion protection and life recovery of a turboshaft engine operating in a marine salt spray environment during overhaul, as described in claim 1, is characterized in that... The corrosion-fatigue coupled remaining life prediction model satisfies the following relationship: in, This represents the fatigue crack propagation rate. This represents the stress intensity factor amplitude. and These are the fatigue performance parameters of the material. For corrosion damage degree, The coefficient is the corrosion-fatigue coupling coefficient. The input parameters include the marine service load spectrum of the part throughout its entire life cycle, corrosion damage detection data, and material performance parameters. The output parameters are the remaining fatigue life and safe service life of the part.

7. The method for systemic corrosion protection and life recovery of a turboshaft engine operating in a marine salt spray environment as described in claim 1, characterized in that, The data from the entire overhaul process includes corrosion detection data, repair process parameters, protective treatment parameters, cleanliness control data, and life prediction results. The above data is stored on the blockchain using consortium blockchain technology, and the data retention period covers the entire life cycle of the engine. A multi-node authorized access mechanism is established to achieve data sharing and airworthiness review.

8. The method for systemic corrosion protection and life recovery of a turboshaft engine operating in a marine salt spray environment according to claim 1, characterized in that, In the nanosecond pulsed laser micro-melting repair process, the average laser power is 50W-150W, the pulse width is 20ns-100ns, the scanning speed is 10mm / s-30mm / s, the spot diameter is 0.5mm-1.0mm, the overlap rate is 30%-50%, and the process is carried out in a high-purity inert gas protective environment.

9. The method for systemic corrosion protection and life recovery of a turboshaft engine operating in a marine salt spray environment during overhaul, as described in claim 1, is characterized in that... The nanocomposite ceramic anti-corrosion layer is a multi-layered alternating structure coating, including a Ti layer, a TiN layer, and a TiAlN layer, with each layer having a thickness of [missing information]. The total thickness is The coating hardness is not less than 2000 HV, and the coating bonding strength is not less than 80 MPa.

10. The method for systemic corrosion protection and life recovery of a turboshaft engine operating in a marine salt spray environment during overhaul, as described in claim 1, is characterized in that... The cleaning process employs a multi-stage cleaning method, including ultrasonic cleaning with deionized water, alkaline degreasing treatment, rinsing with deionized water, and hot air drying. The resistivity of the deionized water is no less than [value missing]. After cleaning, the residual chloride ion content was detected by ion chromatography.

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