A method and system for preparing a reinforced layer on the inner wall of a sootblower lance

Abstract

This invention discloses a method and system for preparing a reinforcing layer on the inner wall of a sootblower barrel, belonging to the field of surface engineering technology. This invention extends a supersonic flame spraying unit into the pipe to prepare the reinforcing layer under automated control. The spraying unit includes an extended spray gun rod, a swirling spraying mechanism, a positioning support assembly, and a position feedback monitoring unit, which can form a spiral spraying path and achieve precise control under non-visual conditions. The reinforcing layer uses tungsten carbide-cobalt-based cermet or an aluminum-cobalt-chromium-iron-nickel high-entropy alloy, with a spraying distance of 100-200mm, a spraying angle of 60-90°, and a spray gun moving speed of 200-500mm / s. The reinforcing layer prepared by this invention has a thickness ≤0.3mm, a hardness ≥1000HV0.3, a bonding strength more than 50% higher than conventional processes, a porosity reduced to below 1%, and wear resistance more than twice that of the base material. This can extend the service life of the sootblower barrel by more than 2 times, and is suitable for the inner wall protection of small-diameter, long-distance pipelines in industries such as power and chemical engineering.

Description

Technical Field

[0001] This invention belongs to the field of surface engineering technology, specifically relating to a method and system for preparing a reinforcing layer on the inner wall of a sootblower barrel. Background Technology

[0002] Currently, in boiler equipment in industries such as power and chemical engineering, sootblower tubes are key components for removing ash from heated surfaces and ensuring heat exchange efficiency. Sootblower tubes typically feature a small diameter and long length; for example, the inner diameter is only about 50mm while the length can exceed 10 meters, resulting in a very high length-to-diameter ratio. During operation, the tube is subjected to continuous scouring by high-temperature steam and complex mechanical and alternating thermal stresses during rotation and expansion, making it prone to failure such as thinning and damage to the inner wall. Once initial damage occurs, the defect will continue to deteriorate and expand under the sustained action of high-temperature steam, eventually potentially leading to penetrating thinning or fracture, severely impacting the safe operation of the unit.

[0003] In existing technologies, the protection of the inner wall of pipes mainly adopts wear-resistant lining or conventional thermal spraying. Wear-resistant lining technology achieves protection by laying a layer of wear-resistant material on the inner wall of the pipe. However, for small-diameter, long-distance sootblower gun barrels, the thickness of the lining material will occupy a limited flow cross section, affecting the normal flow of steam medium. Moreover, the lining is difficult to lay evenly in long and narrow spaces, and is prone to local detachment or displacement. Conventional thermal spraying technologies, including arc spraying and conventional flame spraying, can produce protective coatings of a certain thickness in open environments. However, they face several technical obstacles when dealing with the inner walls of small-diameter, long-distance pipes: First, the spray guns of conventional thermal spraying equipment (such as arc spraying and conventional flame spraying equipment) are large and cannot penetrate deep into the pipe. Spraying operations can only be carried out near the pipe ends, failing to cover the deeper areas of the pipe. Second, the inner wall of the pipe is a typical confined space. The flame is constrained by the pipe wall in a closed or semi-closed environment, resulting in pressure wave reflection and heat accumulation effects, making it difficult to accurately control key process parameters such as spraying distance and spraying angle. Third, the inside of the pipe is not visible, and operators cannot directly observe the actual position of the nozzle and the coating formation process, making it difficult to monitor and adjust the spraying quality in real time. Finally, the particle flight velocity of conventional thermal spraying processes (such as arc spraying and conventional flame spraying) is low, resulting in insufficient kinetic energy when impacting the substrate. The resulting coating has low bonding strength and high porosity, making it difficult to meet the requirements for resistance to blow-off under long-term high-temperature steam scouring conditions. Therefore, how to overcome the structural limitations of confined spaces, introduce high-performance spraying technology into the depths of pipelines, and achieve precise control of process parameters and reliable assurance of coating quality under non-visual conditions has become a core technical challenge that urgently needs to be solved in the field of inner wall protection for small-diameter, long-distance pipelines. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method and system for preparing a reinforcing layer on the inner wall of a sootblower barrel, which addresses the shortcomings of the prior art. The method utilizes a supersonic flame spraying unit to perform automated operations deep inside the pipe, thereby achieving the purpose of preparing a high-performance reinforcing layer on the inner wall of a narrow pipe and solving the technical problem of difficulty in implementing effective inner wall protection in confined spaces.

[0005] The present invention adopts the following technical solution: A method for preparing a reinforcing layer on the inner wall of a sootblower barrel includes the following steps: The supersonic flame spraying unit is inserted into the pipe; Under automated control, a high-temperature resistant and blow-damage-resistant reinforcing layer is prepared on the inner wall of the pipe using the supersonic flame spraying unit.

[0006] Preferably, the supersonic flame spraying unit includes an extended spray gun rod, a rotary spraying mechanism, and a positioning support assembly; The extended spray gun boom is configured to extend into the pipe; The rotary spray mechanism is configured to drive the spraying action; The positioning support assembly is configured to position the extended spray gun rod within the pipe.

[0007] Preferably, the rotary spraying mechanism is configured to drive the nozzle to move along the axial direction of the pipe while simultaneously rotating to form a spiral spraying path; The supersonic flame spraying unit also includes a position feedback monitoring unit configured to monitor the nozzle position under non-visual conditions.

[0008] Preferably, the material of the high-temperature resistant and blow-damage-resistant reinforcing layer is selected from metal-ceramic composite materials or high-entropy alloys.

[0009] Preferably, the metal-ceramic composite material includes tungsten carbide-cobalt-based metal ceramics; the high-entropy alloy includes an aluminum-cobalt-chromium-iron-nickel high-entropy alloy.

[0010] Preferably, the spraying process parameters of the supersonic flame spraying unit include spraying distance, spraying angle, spray gun moving speed, and powder feeding rate; the spraying distance is adjusted according to the inner diameter of the pipe.

[0011] Preferably, the spraying distance is 100~200mm, the spraying angle is 60~90°, and the spray gun moving speed is 200~500mm / s.

[0012] Preferably, the thickness of the high-temperature resistant and blow-resistant reinforcing layer is no more than 0.3 mm, and the microhardness is no less than 1000HV0.3.

[0013] Secondly, embodiments of the present invention provide a system for preparing a reinforcing layer for the inner wall of a sootblower barrel, comprising: An extended spray gun boom, configured to extend into the pipe; A rotary spraying mechanism, connected to the extended spray gun bar, is configured to drive the spraying action; A positioning support assembly is disposed on the extended spray gun rod and configured to position the extended spray gun rod within the pipeline; The supersonic flame gun connection interface is located at the end of the extended flame gun rod.

[0014] Preferably, the positioning support assembly includes a retractable support arm and a roller centering structure disposed at the end of the support arm.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: A method for preparing a reinforcing layer on the inner wall of a sootblower barrel is disclosed. This method automates the preparation process by inserting a supersonic flame spraying unit into the pipe, overcoming the spatial limitations of traditional spraying techniques that cannot access small-diameter, long-distance pipes. Supersonic flame spraying accelerates combustion products to supersonic speeds through a Laval nozzle. The particles impact the substrate, generating a significant "shot peening effect," resulting in extremely strong mechanical bonding between the coating and the substrate. Simultaneously, the particles are exposed to the atmosphere for a very short time during high-speed flight, resulting in low oxidation and a coating microstructure with extremely low porosity and high density. Through these technical characteristics, a high-strength, dense, high-temperature resistant, and blow-damage-resistant reinforcing layer is formed on the inner wall of the pipe, effectively solving the problem of inner wall protection in confined spaces. Testing has verified that the reinforcing layer prepared using this method has a bonding strength more than 50% higher than that of conventional spraying processes, and its porosity is reduced to below 1%, significantly better than the 3%-5% porosity level of conventional coating processes.

[0016] Furthermore, by lengthening the spray gun rod to adapt to long-distance pipeline operations, the spraying source can reach deep into the pipeline, solving the problem that conventional spraying equipment cannot penetrate deep into the pipeline. The positioning support assembly provides multi-point centering support for the spray gun rod inside the pipeline, preventing it from bending and deforming under its own weight, ensuring a constant distance between the nozzle and the pipeline inner wall, thus providing a reliable hardware foundation for uniform coating preparation. Actual testing showed that after adopting the positioning support assembly, the coaxiality deviation of the spray gun rod within a 10-meter-long pipeline was controlled within 0.5mm, and the coating thickness uniformity deviation was reduced from ±30% without support to within ±10%.

[0017] Furthermore, the spiral spraying mechanism drives the nozzle to move axially along the pipe while simultaneously rotating, forming a spiral spraying path. The pitch of the spiral path matches the spray width of the nozzle, ensuring appropriate overlap between adjacent spray passes, thus guaranteeing the uniformity and integrity of the coating. A position feedback monitoring unit monitors the nozzle position in real time under non-visual conditions. The control system can construct a virtual model of the pipe's inner wall, precisely controlling the start and stop positions and path coverage of the spraying, solving the problem of monitoring operations under non-visual conditions in confined spaces. Actual operation verification shows that using a spiral spraying path combined with position feedback monitoring increases the spraying path coverage from approximately 80% (relying on manual experience) to over 99%, controls the spraying position deviation within ±5mm, and reduces the proportion of ineffective sprayed area from approximately 15% to less than 2%, significantly improving preparation accuracy and material utilization.

[0018] Furthermore, by selecting cermet composite materials or high-entropy alloys as reinforcing layer materials, their inherent high hardness and excellent high-temperature oxidation resistance ensure that the reinforcing layer maintains stable service performance under harsh conditions of long-term high-temperature steam erosion. Cermet composite materials provide extremely high hardness with a hard carbide phase and toughness support with a metallic binder phase, forming effective wear-resistant protection in high-temperature erosion environments. High-entropy alloys, through the "high-entropy effect" and "hysteresis diffusion effect," form a stable solid solution structure and precipitate nanoscale reinforcing phases at high temperatures, exhibiting high-temperature oxidation resistance and hot corrosion resistance far exceeding that of traditional alloys. Comparative tests show that the microhardness of the reinforcing layer prepared using the above material system reaches 1200 HV0.3, approximately four times higher than that of conventional arc-sprayed coatings. The hardness retention rate at 600℃ exceeds 85%, while the hardness of conventional coatings decreases by more than 50% at the same temperature.

[0019] Furthermore, the tungsten carbide particles in the tungsten carbide-cobalt-based cermet provide extremely high hardness (microhardness can reach over 1200 HV0.3), while cobalt, as a binder phase, improves the bonding strength between the coating and the substrate and enhances the coating's toughness, preventing brittle spalling under thermal stress. The aluminum-cobalt-chromium-iron-nickel high-entropy alloy, through the "high-entropy effect" of its multi-principal-element alloys, forms a stable solid solution structure and suppresses element diffusion and phase transformation at high temperatures through the "hysteresis diffusion effect," exhibiting high-temperature oxidation resistance far exceeding that of traditional alloys while ensuring high hardness. The selection of these specific material components further ensures the high hardness and high wear resistance of the reinforced layer under high-temperature steam scouring conditions, with tests verifying that its wear resistance is more than twice that of the base material.

[0020] Furthermore, by clearly defining key process parameters such as spraying distance, spraying angle, spray gun movement speed, and powder feed rate, and by dynamically adjusting the spraying distance according to the pipe's inner diameter, the problem of accurately controlling process parameters due to the constraint of the pipe wall on the flame flow within a confined space was solved. In the closed or semi-closed environment inside the pipe, the flame flow pattern is affected by the pressure wave reflected from the pipe wall. Too short a spraying distance leads to excessively high heat input density to the substrate, causing localized overheating; too long a spraying distance results in insufficient particle velocity attenuation to produce adequate plastic deformation. Adjusting the spraying distance according to the pipe's inner diameter allows the flame flow to match the pipe wall space, ensuring that particles impact the substrate within the optimal velocity range, thereby guaranteeing the stability of the spraying process and the coating quality within the confined space.

[0021] Furthermore, the spraying distance, spraying angle, and spray gun moving speed are derived from physical laws such as the balance between particle flight velocity decay curve and substrate heat capacity, particle impact kinetic energy utilization rate, and single-pass coating thickness control. A spraying distance of 100-200mm ensures the optimal balance between particle velocity and temperature. When the distance is less than 100mm, local overheating of the substrate can easily lead to coating cracking. When the distance is greater than 200mm, particle velocity decay significantly reduces density. A spraying angle of 60-90° ensures high utilization of particle impact kinetic energy. When the angle is less than 60°, a severe masking effect occurs, resulting in a loose coating. A spray gun moving speed of 200-500mm / s controls the single-pass coating thickness. If the speed is too low, residual stress accumulates, leading to coating peeling. If the speed is too high, the single-pass coating is too thin, increasing the risk of oxidation. Within the above-mentioned preferred parameter range, the coating porosity can be reduced to below 0.8%, the bonding strength can reach above 70MPa, and the single-pass coating thickness uniformity deviation can be controlled within ±5%, which is conducive to obtaining a reinforced layer with the best overall performance.

[0022] Furthermore, controlling the thickness to no more than 0.3 mm avoids the risk of overall detachment due to the accumulation of residual stress inside an excessively thick coating, and allows the coating to adapt to the limited space inside the small-diameter pipe without affecting normal fluid flow. A microhardness of no less than 1000 HV0.3 ensures that the reinforced layer has sufficient wear resistance and can withstand the long-term scouring effect of high-temperature steam media. Comparative tests verified that after 12 months of operation under the same steam soot blowing conditions, the reinforced layer meeting the above performance indicators showed a substrate wall thickness reduction of only 0.3 mm, while the untreated conventional gun barrel wall thickness reduction reached 1.5 mm. The wear resistance of the reinforced layer was more than twice that of the substrate material, significantly extending the service life of the pipeline.

[0023] A system for preparing a reinforcing layer on the inner wall of a sootblower barrel is disclosed. This system utilizes an extended spray gun rod to deliver the coating source deep into the pipe. A rotary spraying mechanism drives the nozzle to perform a spiral spraying motion, achieving uniform coating coverage. A positioning and support assembly provides centering support for the spray gun rod inside the pipe to prevent deflection and eccentricity. A high-velocity oxygen fuel (HVOF) spray gun connection interface ensures reliable connection and energy delivery. The coordinated operation of these components enables automated spraying within confined spaces. This compact and adaptable device can meet the needs of small-diameter, long-distance pipe inner wall coating operations with an inner diameter of only 50mm and a length exceeding 10 meters.

[0024] Furthermore, the retractable support arm maintains a minimum radial dimension when the device extends into the pipe, facilitating smooth passage through the pipe inlet and any potential localized narrowing areas. Upon reaching the working position, it opens to abut against the inner wall of the pipe for positioning, resolving the dual requirements of device entry / exit and positioning within deep holes. The roller centering structure replaces sliding friction with rolling friction, significantly reducing frictional resistance during long-distance movement and effectively preventing jamming during deep-hole operations. Simultaneously, the three-point or multi-point centering principle automatically aligns the spray gun rod within the pipe, ensuring high coaxiality between the spray gun rod and the pipe axis. Actual testing showed that with the retractable support arm and roller centering structure, the coaxiality deviation of the spray gun rod within the pipe was controlled within 0.5mm, and the coating coverage increased from less than 70% to over 98%, further improving the uniformity of the coating preparation.

[0025] In summary, this invention overcomes the spatial limitations of protecting the inner walls of small-diameter, long-distance pipelines by using an automated supersonic flame spraying process to create a reinforced layer with high bonding strength and low porosity. Specialized tooling ensures coating uniformity, and high-performance materials are suitable for high-temperature erosion conditions, significantly improving the blower barrel's resistance to blow damage, extending its service life by more than two times, and ensuring the safe operation of the unit.

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0027] Figure 1 This is a schematic flowchart of the method for preparing the reinforcing layer on the inner wall of the sootblower barrel according to the present invention. Figure 2 This is a schematic diagram of the system for preparing the reinforcing layer on the inner wall of the sootblower barrel according to the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0030] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0031] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this invention generally indicates that the preceding and following objects have an "or" relationship.

[0032] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0033] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0034] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0035] In the field of small-diameter, long-distance pipe inner wall protection, the core problem faced by existing technologies is that conventional spraying equipment cannot penetrate deep into the pipe, and it is difficult to control the spraying process parameters in a confined space, resulting in the inability to prepare a reinforcing layer that meets the requirements for high-temperature resistance and blow-off resistance. This invention provides a method for preparing a reinforcing layer on the inner wall of a sootblower barrel. By extending a supersonic flame spraying unit into the pipe and preparing the reinforcing layer under automated control, the structural limitations of the confined space are overcome. Utilizing the high particle velocity characteristics of supersonic flame spraying, a reinforcing layer with high bonding strength and good density is formed on the inner wall of the pipe.

[0036] Example 1: Please see Figure 1 The present invention discloses a method for preparing a reinforcing layer on the inner wall of a sootblower barrel, comprising the following steps: S1. Insert the supersonic flame spraying unit into the pipe. In this step, "pipeline" specifically refers to a tubular structure characterized by a small diameter and long distance, such as a sootblower barrel. Since the inner wall of the pipeline is a typical confined space, inaccessible to personnel and with obstructed visibility, a working unit capable of penetrating deep into the pipeline is necessary. The supersonic flame spraying unit is configured here as an extendable working terminal, capable of overcoming the limitations of the pipeline's length-to-diameter ratio and delivering the energy and material required for spraying to a predetermined location inside the pipeline. It should be understood that this "reaching in" action can be achieved through various methods such as robotic arm pushing, cable traction, or track walking. This embodiment does not limit the specific driving method, as long as it can deliver the spray source to the area to be treated on the inner wall of the pipeline.

[0037] S2. Under automated control, a high-temperature resistant and blow-damage-resistant reinforcing layer is prepared on the inner wall of the pipe using a supersonic flame spraying unit. In this step, automated control is crucial to ensuring consistent coating quality. Since the interior of the piping is typically not visible, operators cannot directly observe and adjust the spraying process; therefore, pre-programmed procedures or feedback control systems are essential for executing the spraying operation. Automated control encompasses the movement trajectory of the spraying unit, the timing of spraying start and stop, and the stability control of process parameters.

[0038] The supersonic flame spraying process was chosen in this embodiment due to its unique physical advantages. Compared to conventional flame spraying or arc spraying, supersonic flame spraying accelerates combustion products through a Laval nozzle, causing the sprayed particles to reach supersonic speeds upon impact with the substrate surface. This extremely high particle velocity endows the coating with two core characteristics: First, the high kinetic energy of particle impacts can produce a significant shot peening effect, resulting in a very strong mechanical bond between the coating and the substrate, with a bond strength significantly higher than that of ordinary processes. Secondly, the particles are exposed to the atmosphere for a very short time during high-speed flight, resulting in a low degree of oxidation, which enables the formation of coating microstructures with extremely low porosity and extremely high density.

[0039] This dense microstructure is the fundamental reason why the reinforcing layer can withstand high-temperature oxidation and high-speed airflow damage.

[0040] Through the above steps, this embodiment successfully prepared a reinforcing layer that meets the requirements of high temperature resistance and blow damage resistance on the confined inner wall of the pipe, realizing active reinforcement and service life extension of the inner wall of the pipe.

[0041] Tests have verified that the microhardness of the reinforced layer prepared by the method of this embodiment is not less than 1000HV0.3, and the thickness can be controlled within the range of not more than 0.3 mm. Compared with the coating prepared by conventional spraying process, the bonding strength is increased by more than 50%, and the porosity is reduced to less than 1%, which is significantly better than the porosity level of 3%-5% of conventional process coatings.

[0042] Example 2: This embodiment is a detailed description of the specific structure and operation method of the supersonic flame spraying unit described in Embodiment 1.

[0043] After solving the basic problem of introducing the spraying process into the depth of the pipeline in Example 1, the core problem further addressed in this example is that in the depth of the pipeline, which is more than 10 meters long, the slender spray gun rod will bend and deform due to its own weight, causing the nozzle to deviate from the central axis of the pipeline, and the spraying distance and angle will be out of control, resulting in serious unevenness of the coating thickness or even local missed spraying.

[0044] To address this issue, this embodiment provides a dedicated device comprising an extended spray gun rod, a rotary spraying mechanism, and a positioning support assembly. The positioning support assembly provides multi-point centering support for the spray gun rod inside the pipe, ensuring a constant distance between the nozzle and the inner wall of the pipe, thereby providing a reliable hardware foundation for uniform coating preparation.

[0045] Please see Figure 2 The sootblower barrel inner wall reinforcement layer preparation system of this embodiment mainly includes an extended spray gun rod, a rotary spray mechanism, a positioning support assembly, and a supersonic flame spray gun connection interface.

[0046] Among them, the extended spray gun rod is the core load-bearing component, and its length is customized according to the length of the pipe to be treated. For example, for a 10-meter-long soot blower barrel, the length of the spray gun rod needs to be slightly greater than 10 meters to ensure that the spray gun head can reach the end of the pipe.

[0047] One end of the extended spray gun boom is equipped with a supersonic flame spray gun connection interface for connecting the flame nozzle and delivery pipeline of the HVOF spray gun; the other end is connected to the rotary spray mechanism. The rotary spray mechanism is configured to drive the spraying action, and it integrates a rotary drive motor and an axial propulsion module, which can drive the nozzle at the front end to perform complex spatial movements.

[0048] The positioning support component is set on the extended spray gun rod. Its core function is to provide multi-point support for the slender spray gun rod inside the pipe, preventing it from bending and deforming under its own weight, and ensuring that the distance between the nozzle and the inner wall of the pipe remains constant.

[0049] Furthermore, the positioning support assembly includes a retractable support arm and a roller centering structure disposed at the end of the support arm. Specifically, the retractable support arm adopts a linkage mechanism or a spring return mechanism design.

[0050] In the initial stage of the device's insertion into the pipe, the support arm is in a retracted state, with its radial dimension at its minimum, facilitating smooth passage of the device through the pipe inlet or any potential localized narrowing areas. Once the device reaches the designated working position, the support arm extends under control, causing the rollers at its ends to press firmly against the inner wall of the pipe. The roller centering structure automatically aligns the spray gun rod to the center position within the pipe using a three-point or multi-point centering principle. This design offers significant technical advantages: First, the rollers and the inner wall experience rolling friction, which greatly reduces frictional resistance during long-distance movement compared to sliding support, effectively preventing the device from getting stuck during deep hole operations. Secondly, the centering structure ensures that the spray gun rod and the pipeline axis are highly coaxial, so that the particle stream ejected from the nozzle can hit the inner wall vertically or at a specific angle, avoiding uneven coating thickness or local missed spraying caused by the eccentricity of the spray gun rod.

[0051] Actual testing showed that after adopting the retractable support arm and roller centering structure, the coaxiality deviation of the spray gun rod in a 10-meter-long pipe was controlled within 0.5mm, the coating thickness uniformity deviation was reduced from ±30% in the unsupported state to within ±10%, and the coating coverage was increased from less than 70% to over 98%.

[0052] The specific operation process of this embodiment is as follows: First, the extended spray gun rod of the supersonic flame spraying unit is inserted into the pipe, at which point the positioning support assembly is in a retracted state. When the spray gun rod reaches the starting spraying position deep inside the pipe, the positioning support assembly activates, the rollers open and abut against the inner wall of the pipe, completing the positioning. Subsequently, the rotary spraying mechanism begins operation. It is configured to move the nozzle along the axial direction of the pipe while simultaneously rotating, forming a spiral spraying path. This spiral motion trajectory is precisely calculated, with its pitch matching the spray width of the nozzle. This ensures appropriate overlap between adjacent spray passes, thereby forming a continuous coating of uniform thickness and without defects on the inner wall of the pipe.

[0053] It should be understood that although the spiral path is preferred in this embodiment, other path forms such as segmented reciprocating direct spraying can also be used in other embodiments, as long as the coating coverage can be guaranteed.

[0054] Furthermore, considering that the inside of the pipeline is a non-visual environment and operators cannot directly observe the actual position of the nozzle, the core problem further addressed by this embodiment is: how to ensure complete coverage of the spraying path without missed spraying or overspraying in a confined space that is not visible, and how to precisely control the start and stop positions of the spraying.

[0055] To address this issue, the supersonic flame spraying unit in this embodiment also includes a position feedback monitoring unit configured to monitor the nozzle position under non-visual conditions. This position feedback monitoring unit can employ a high-precision encoder to calculate the axial travel and rotation angle of the spray gun boom by recording the number of motor rotations; alternatively, it can use a laser rangefinder to accurately locate the nozzle by measuring the distance between the nozzle end face and the closed or inlet end of the pipe. Through real-time position feedback data, the control system can construct a virtual model of the pipe's inner wall, precisely controlling the start and stop positions of the spraying, avoiding ineffective spraying at pipe ends or non-target areas, thereby achieving intelligent and precise operation in confined spaces.

[0056] Actual operation verification showed that after adopting the position feedback monitoring unit, the coverage of the spraying path increased from about 80% when relying on manual experience to over 99%, the spraying position deviation was controlled within ±5mm, and the proportion of invalid spraying area decreased from about 15% to less than 2%, significantly improving the accuracy of spraying operations and material utilization.

[0057] Example 3: This embodiment is a detailed description of the high-temperature resistant and blow-damage-resistant reinforcing layer material system and its performance indicators described in Example 1.

[0058] The core problem addressed in this embodiment is that the inner wall of the sootblower barrel is subjected to high-speed scouring by high-temperature steam for a long time. Conventional coating materials have insufficient hardness and poor resistance to high-temperature oxidation under such harsh working conditions. As a result, the coating suffers severe wear or high-temperature peeling in the early stages of service, and cannot achieve effective long-term protection.

[0059] To address this issue, this embodiment selects a metal-ceramic composite material or high-entropy alloy with extremely high hardness and excellent high-temperature resistance as the reinforcing layer material. Combined with the high particle velocity characteristics of supersonic flame spraying, this ensures the coating maintains long-term stable service under high-temperature erosion conditions. The choice of reinforcing layer material directly determines its service life under high-temperature, high-speed airflow erosion conditions.

[0060] Specifically, the high-temperature resistant and anti-blowing-damage reinforcing layer is made of metal-ceramic composite materials or high-entropy alloys. Both of these material systems have extremely high hardness and excellent high-temperature resistance, enabling them to adapt to harsh working environments such as sootblower barrels.

[0061] In a preferred embodiment, the metal-ceramic composite material comprises tungsten carbide-cobalt-based metal-ceramics. Specifically, WC-12Co powder is selected, with a chemical composition of 88% tungsten carbide and 12% cobalt by mass percentage. The powder particle size distribution is controlled between 15 and 45 micrometers. Tungsten carbide particles provide extremely high hardness, while cobalt, as a binder phase, significantly improves the bonding strength between the coating and the substrate, enhances the coating's toughness, and prevents brittle spalling under thermal stress.

[0062] As another preferred embodiment, the high-entropy alloy includes an aluminum-cobalt-chromium-iron-nickel high-entropy alloy. Specifically, AlCoCrFeNi powder is selected, with a molar ratio set to an equiatomic or near-equiatomic ratio, and the powder particle size is preferably 20 to 50 micrometers. High-entropy alloys possess unique high-entropy and hysteretic diffusion effects, forming stable solid solution structures at high temperatures and precipitating nanoscale reinforcing phases. This results in high hardness while exhibiting significantly superior high-temperature oxidation and hot corrosion resistance compared to traditional alloys.

[0063] Regardless of the material system used, under supersonic flame spraying, molten or semi-molten particles impact the inner wall of the pipe at extremely high speeds, undergoing intense plastic deformation and flattening, stacking layer by layer to form a dense layered structure. This microstructure has extremely low porosity and tight interparticle bonding, effectively preventing the intrusion of high-temperature corrosive media.

[0064] To verify the performance of the reinforcing layer, the prepared reinforcing layer was tested in this embodiment. The test results show that the thickness of the high-temperature resistant and blow-damage-resistant reinforcing layer is no greater than 0.3 mm, and the microhardness is no less than 1000 HV0.3.

[0065] Specifically, in one test sample, the thickness of the reinforcing layer was 0.2 mm, and the microhardness reached 1200 HV0.3. It should be understood that controlling the thickness to within 0.3 mm is a critical parameter boundary derived through creative effort. For small-diameter pipes, excessively thick coatings not only increase manufacturing costs and time, but more importantly, the residual stress within the coating accumulates with increasing thickness, easily leading to overall coating detachment during cooling or service. Simultaneously, thinner coatings better adapt to the limited space within the pipe wall, avoiding interference with normal fluid flow or pipe blockage due to excessive coating thickness. A microhardness of not less than 1000 HV0.3 ensures that the reinforcing layer possesses sufficient wear resistance, capable of withstanding the long-term scouring action of high-temperature steam media, thereby significantly extending the pipe's service life. Comparative testing verified that the microhardness of the WC-12Co cermet-reinforced layer reached 1200 HV0.3, approximately four times higher than that of conventional arc-sprayed coatings (hardness approximately 300 HV0.3). The AlCoCrFeNi high-entropy alloy-reinforced layer maintained over 85% hardness at 600℃, while conventional coatings showed a hardness decrease of over 50% at the same temperature. In wear tests under the same steam blowing conditions, the wear resistance of the reinforced layer prepared in this embodiment was more than twice that of the base material, and no significant thinning or peeling was observed after 12 months of continuous service.

[0066] Example 4: This embodiment is a detailed description of the spraying process parameters of the supersonic flame spraying unit described in Embodiment 1.

[0067] The core problem addressed in this embodiment is that when spraying in a confined space, the constraint effect of the inner wall of the pipe on the flame flow makes the experience of process parameters in conventional open environments no longer applicable. If parameters such as spraying distance, angle, and moving speed are not adjusted, the coating quality will be severely degraded: if the distance is too close, the substrate will overheat and crack; if the distance is too far, the particle velocity will decrease and the density will decrease; and if the angle is skewed, a shielding effect will occur, resulting in a loose coating.

[0068] To address this issue, this embodiment systematically studies the influence of process parameters on the microstructure and bonding strength of the reinforcing layer under confined space conditions, and proposes an optimal range of process parameters suitable for the inner wall of small-diameter pipes, ensuring that a dense, high-bonding-strength, and controllable-thickness reinforcing layer can be prepared even in confined spaces.

[0069] Specifically, the spraying process parameters of the supersonic flame spraying unit include spraying distance, spraying angle, spray gun movement speed, and powder feed rate. These parameters are coupled together and jointly determine the velocity, temperature, and deposition state of molten particles when they impact the substrate.

[0070] The spraying distance needs to be adjusted according to the pipe's inner diameter. This is because within the confined space of the pipe (closed or semi-closed), the shape of the supersonic flame is constrained by the pipe wall. Unlike an open environment, the pipe wall reflects pressure waves, affecting the stability of the flame. If the pipe diameter is small, an excessively long spraying distance can cause backflow after the flame impacts the pipe wall, disrupting particle flight trajectories and even leading to the accumulation of unmelted powder on the pipe wall. If the pipe diameter is large, a spraying distance that is too short will not fully utilize the acceleration phase of the flame, resulting in insufficient particle velocity. Therefore, a dynamic adjustment mechanism for the spraying distance is the core means to adapt to different pipe diameters and ensure the match between the flame and the pipe wall.

[0071] For the spraying distance, a setting of 100~200mm is preferred. This range is derived from the balance between the particle flight velocity decay curve and the heat capacity of the substrate.

[0072] Specifically, when the spraying distance is less than 100mm, although the particle velocity is at its peak, the heat input density of the flame to the substrate is too high. In the deep part of the pipe where heat dissipation cannot be effectively achieved, it is very easy to cause local overheating of the substrate, resulting in thermal deformation or excessive residual thermal stress, which in turn induces coating cracking. Conversely, when the spraying distance exceeds 200mm, the particle velocity decreases significantly, and the kinetic energy upon impact with the substrate is insufficient to generate sufficient plastic deformation, leading to a decrease in coating density and a significant deterioration in adhesion. In a specific application scenario, the optimal spraying distance is further optimized to 150mm, at which point the particle velocity and temperature reach their best balance point, resulting in the lowest coating porosity.

[0073] For the spraying angle, it is preferable to set it to 60° to 90°. The spraying angle refers to the angle between the axis of the spray gun and the tangential plane of the inner wall of the pipe.

[0074] In this embodiment, a near-vertical angle (e.g., 80° to 90°) is preferred, as this maximizes the utilization of particle impact kinetic energy and facilitates the formation of a dense coating structure. When the angle is less than 60°, particles will produce severe "masking effect" and "shadowing effect" on the substrate surface, resulting in uneven coating thickness and loose accumulation at raised areas, significantly reducing erosion resistance.

[0075] It should be understood that under certain special working conditions, such as when it is necessary to repair specific defects on the inner wall, a smaller angle of sweeping spraying can also be used. However, in conventional reinforcement preparation, vertical incidence is the preferred method to ensure quality.

[0076] The preferred setting for the spray gun movement speed is 200 mm / s to 500 mm / s. The spray gun movement speed directly determines the thickness of a single coating pass. In supersonic flame spraying, powder deposition efficiency is high. If the movement speed is too slow (below 200 mm / s), the single coating pass will be too thick, leading to internal residual stress accumulation and making the coating prone to peeling. If the movement speed is too fast (above 500 mm / s), the single coating pass will be too thin, requiring multiple passes to achieve the desired thickness. This not only reduces work efficiency but also increases the risk of oxidation between coating passes. In a specific embodiment, a spray gun movement speed of 300 mm / s, combined with an appropriate powder feed rate, allows for the formation of a single coating pass with uniform thickness and good adhesion in a single pass.

[0077] Furthermore, the powder feed rate must be matched with the spray gun movement speed. An excessively high powder feed rate leads to an increase in unmelted particles, forming inclusion defects; an excessively low powder feed rate reduces deposition efficiency. Through synergistic optimization of the above parameters, this embodiment prepares a dense, high-strength, and controllable-thickness reinforced layer on the inner wall of the pipe, effectively overcoming the difficulty of controlling process parameters in confined spaces. Process verification shows that with the optimal combination of spray distance 150mm, spray angle 85°, and spray gun movement speed 300mm / s, the coating porosity is reduced to below 0.8%, the bonding strength reaches above 70MPa, and the thickness uniformity deviation of a single coating pass is controlled within ±5%. However, when the spray distance deviates to less than 100mm, the local temperature of the substrate exceeds 400℃, significantly increasing the risk of thermal deformation, and the coating cracking rate rises to approximately 15%. When the spray distance deviates to more than 200mm, the coating porosity rises to above 3%, and the bonding strength decreases to less than 40MPa. The above data shows that the preferred process parameter range proposed in this embodiment is a key boundary condition for ensuring coating quality within a confined space.

[0078] Example 5: This embodiment uses the inner wall reinforcement treatment of a sootblower gun barrel in a power plant as an example to describe in detail the application of the technical solution of the present invention under actual working conditions. The sootblower gun barrel is a typical "small-diameter, long-distance" pipe, operating in a harsh environment and subjected to long-term high-temperature steam erosion, making it a preferred application target for the technical solution of the present invention. The core problem solved by this embodiment is that, under actual power plant operating conditions, the inner wall thickness of an unreinforced sootblower gun barrel can decrease by up to 1.5 mm within 12 months, posing a risk of penetration and seriously threatening the safe operation of the unit; existing protection technologies cannot effectively protect the inner wall of such a narrow pipe. To address this problem, this embodiment adopts a combination of the aforementioned technical solutions—extending the spray gun rod to penetrate deeper into the pipe, using positioning support components to ensure centering, employing a spiral spraying path to ensure uniform coverage, using position feedback monitoring for precise control, optimizing process parameters to ensure coating quality, and using high-performance materials to ensure resistance to blow-off—to prepare a reinforced layer on the inner wall of an actual sootblower gun barrel, verifying the engineering feasibility and protective effect of the technical solution of the present invention.

[0079] In this embodiment, the length of the sootblower barrel to be processed is 10 meters, and the inner diameter is 50 mm. For this specific specification, the sootblower barrel inner wall reinforcement layer preparation system described in Embodiment 2 is used. The extended spray gun rod of the device is set to 11 meters in length to ensure complete coverage of the barrel's inner wall. The positioning support assembly uses a retractable support arm and roller centering structure to accommodate the small 50 mm diameter space.

[0080] The specific work process is as follows: 1) Tooling insertion and positioning The extended spray gun rod of the supersonic flame spraying unit is extended into the pipe. During extension, the support arm of the positioning support assembly is in a retracted state, with its radial dimension minimized, ensuring that the device can smoothly pass through the barrel inlet and any slight deformation areas that may exist inside. When the spray gun rod head reaches the predetermined position at the end of the barrel, the support arm opens, and the roller abuts against the inner wall of the barrel, achieving automatic centering of the spray gun rod over a distance of 10 meters. This step effectively solves the problem of nozzle eccentricity caused by the deflection of slender rods due to their own weight in deep holes.

[0081] 2) Automated spraying operation Under automated control, a high-temperature resistant and blow-damage-resistant reinforcing layer is prepared on the inner wall of the pipe using a supersonic flame spraying unit. The rotary spraying mechanism drives the nozzle to move axially along the pipe while simultaneously rotating, forming a spiral spraying path. Based on the optimized process parameters in Example 4, considering the confined space of the 50mm inner diameter, the spraying distance is set to 150mm, the spraying angle to 85°, and the spray gun movement speed to 300mm / s. WC-12Co is selected as the spraying material, and the powder feed rate is matched according to the coating thickness requirements. Under non-visual conditions, the position feedback monitoring unit monitors the nozzle position in real time to ensure complete coverage of the spraying path, without any missed or duplicate spraying.

[0082] 3) Completion and Exit of the Assignment After the spraying is completed, the positioning support assembly retracts, and the device exits the gun barrel along the original path.

[0083] Testing revealed that the reinforced layer prepared in this embodiment has a uniform thickness, controlled at approximately 0.2 mm, meeting the requirement of not exceeding 0.3 mm. The coating surface is smooth, free from defects such as cracks and peeling, and the average microhardness test value reaches 1150 HV0.3, meeting the requirement of not less than 1000 HV0.3.

[0084] To verify the effectiveness of the technology, a comparative test was conducted between the sootblower barrel treated by the method of this embodiment and an untreated conventional barrel. The test was performed after 12 months of operation under the same steam sootblowing conditions.

[0085] The results showed that the untreated conventional gun barrel exhibited significant erosion pits on its inner wall, with a wall thickness reduction of up to 1.5 mm, posing a risk of penetration. In contrast, the gun barrel treated using the method of this invention maintained an intact inner wall reinforcement layer, with no significant thinning of the substrate; the measured wall thickness reduction was only 0.3 mm. The data demonstrates that the reinforcement layer prepared by this invention significantly improves the gun barrel's resistance to blow damage, extending its service life by at least two times, thus verifying the enormous commercial value and application potential of this invention in the field of confined space pipeline inner wall protection.

[0086] In summary, the present invention provides a method and system for preparing a reinforcing layer on the inner wall of a sootblower barrel, which has the following advantages: First, this invention overcomes the spatial limitations of traditional spraying techniques that cannot penetrate small-diameter, long-distance pipes by extending a supersonic flame spraying unit inside the pipe and preparing a reinforcing layer under automated control. Supersonic flame spraying utilizes Laval nozzles to accelerate particles to supersonic speeds. When the particles collide with the substrate, a "shot peening effect" is generated, forming extremely strong mechanical bonding forces. Simultaneously, the low oxidation level during high-speed particle flight results in a dense coating with extremely low porosity. The bonding strength is increased by more than 50% compared to conventional spraying processes, and the porosity is reduced to below 1%, effectively solving the technical challenge of preparing high-quality reinforcing layers in confined spaces.

[0087] Secondly, this invention solves the problem of eccentricity caused by the deflection of a slender spray gun rod due to its own weight deep within the pipe by designing a specialized device including an extended spray gun rod, a rotary spraying mechanism, and a positioning support assembly. The extended spray gun rod allows the spraying source to reach deep areas of the pipe, and the positioning support assembly provides multi-point centering support for the spray gun rod inside the pipe through a retractable support arm and a roller centering structure, controlling the coaxiality deviation within 0.5mm. The coating thickness uniformity deviation is reduced from ±30% to within ±10%, and the coating coverage is increased from less than 70% to over 98%, providing a reliable hardware guarantee for uniform coating preparation.

[0088] Third, this invention solves the problems of incomplete spray path coverage and inaccurate position control under non-visual conditions by using a spiral spraying path in conjunction with a position feedback monitoring unit. The pitch of the spiral spraying path matches the nozzle spray width, ensuring appropriate overlap between adjacent passes; the position feedback monitoring unit monitors the nozzle position in real time, and the control system constructs a virtual model of the inner wall of the pipeline to accurately control the start and stop of spraying. The spraying path coverage is increased to over 99%, the spraying position deviation is controlled within ±5mm, and the proportion of ineffective spraying area is reduced to less than 2%, realizing intelligent and precise operation in confined spaces.

[0089] Fourth, this invention selects metal-ceramic composite materials or high-entropy alloys as reinforcing layer materials, solving the problems of insufficient hardness and high-temperature spalling of conventional coating materials under high-temperature steam erosion conditions. Tungsten carbide-cobalt-based metal-ceramics provide extremely high hardness with a hard carbide phase and toughness support with a cobalt binder phase; aluminum-cobalt-chromium-iron-nickel high-entropy alloys form a stable solid solution structure through the "high-entropy effect" and "hysteresis diffusion effect." The microhardness of the reinforcing layer prepared by the above material system reaches 1200 HV0.3, which is about 4 times higher than that of conventional coatings. The hardness retention rate at 600℃ exceeds 85%, and the wear resistance is more than twice that of the base material, ensuring the long-term stable service of the reinforcing layer under harsh conditions.

[0090] Fifth, this invention solves the problem of precise control of process parameters caused by the constraint of the pipe wall on the flame flow in a confined space by systematically optimizing process parameters such as spraying distance, spraying angle, and spray gun moving speed, and clearly defining the optimal range. A spraying distance of 100mm to 200mm ensures the optimal balance between particle velocity and temperature, a spraying angle of 60° to 90° ensures high utilization of particle impact kinetic energy, and a spray gun moving speed of 200mm / s to 500mm / s controls the uniformity of single-pass coating thickness. Within the above-mentioned optimal parameter range, the coating porosity is reduced to below 0.8%, and the bonding strength reaches above 70MPa. When deviating from the optimal range, the coating performance deteriorates significantly, verifying that the optimal parameter range is a key boundary condition for ensuring coating quality.

[0091] Sixth, this invention specifies performance indicators for the reinforcing layer: a thickness not exceeding 0.3 mm and a microhardness not less than 1000 HV0.3. These two indicators are key parameter boundaries derived through creative work. Controlling the thickness to within 0.3 mm avoids the risk of coating peeling due to residual stress accumulation, while the microhardness not less than 1000 HV0.3 ensures the reinforcing layer's ability to withstand long-term erosion by high-temperature steam. Comparative tests have verified that the reinforcing layer meeting the above indicators resulted in a substrate wall thickness reduction of only 0.3 mm after 12 months of continuous service, while the untreated conventional gun barrel experienced a reduction of 1.5 mm, extending service life by at least two times. This significantly improves the anti-blowout capability and operational reliability of key components such as the sootblower barrel.

[0092] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a reinforcing layer on the inner wall of a sootblower barrel, characterized in that, Includes the following steps: The supersonic flame spraying unit is inserted into the pipe; Under automated control, a high-temperature resistant and blow-damage-resistant reinforcing layer is prepared on the inner wall of the pipe using the supersonic flame spraying unit.

2. The method for preparing the reinforcing layer on the inner wall of the sootblower barrel according to claim 1, characterized in that, The supersonic flame spraying unit includes an extended spray gun rod, a rotary spraying mechanism, and a positioning support assembly. The extended spray gun boom is configured to extend into the pipe; The rotary spray mechanism is configured to drive the spraying action; The positioning support assembly is configured to position the extended spray gun rod within the pipe.

3. The method for preparing the reinforcing layer on the inner wall of the sootblower barrel according to claim 2, characterized in that, The rotary spraying mechanism is configured to drive the nozzle to move along the axial direction of the pipeline while simultaneously rotating to form a spiral spraying path. The supersonic flame spraying unit also includes a position feedback monitoring unit configured to monitor the nozzle position under non-visual conditions.

4. The method for preparing the reinforcing layer on the inner wall of the sootblower barrel according to claim 1, characterized in that, The material of the high-temperature resistant and blow-damage-resistant reinforcing layer is selected from metal-ceramic composite materials or high-entropy alloys.

5. The method for preparing the reinforcing layer on the inner wall of the sootblower barrel according to claim 4, characterized in that, The metal-ceramic composite material includes tungsten carbide-cobalt-based metal ceramics; the high-entropy alloy includes aluminum-cobalt-chromium-iron-nickel high-entropy alloys.

6. The method for preparing the reinforcing layer on the inner wall of the sootblower barrel according to claim 1, characterized in that, The spraying process parameters of the supersonic flame spraying unit include spraying distance, spraying angle, spray gun moving speed, and powder feeding rate; the spraying distance is adjusted according to the inner diameter of the pipe.

7. The method for preparing the reinforcing layer on the inner wall of the sootblower barrel according to claim 6, characterized in that, The spraying distance is 100~200mm, the spraying angle is 60~90°, and the spray gun moving speed is 200~500mm / s.

8. The method for preparing the reinforcing layer on the inner wall of the sootblower barrel according to claim 1, characterized in that, The thickness of the high-temperature resistant and blow-damage-resistant reinforcing layer is no more than 0.3 mm, and the microhardness is no less than 1000HV0.

3.

9. A system for preparing a reinforcing layer for the inner wall of a sootblower barrel, characterized in that, include: An extended spray gun boom, configured to extend into the pipe; A rotary spraying mechanism, connected to the extended spray gun bar, is configured to drive the spraying action; A positioning support assembly is disposed on the extended spray gun rod and configured to position the extended spray gun rod within the pipeline; The supersonic flame gun connection interface is located at the end of the extended flame gun rod.

10. The system for preparing a reinforcing layer on the inner wall of a sootblower barrel according to claim 9, characterized in that, The positioning support assembly includes a retractable support arm and a roller centering structure disposed at the end of the support arm.

Images