Thermal spraying Ni / Cr alloy coating and preparation method thereof

Abstract

The invention belongs to the field of metal material processing, and particularly relates to a thermal spraying Ni / Cr alloy coating and a preparation method thereof.The coating comprises, by weight, 44%-46% of Cr, 0.5%-1.0% of Ti, 1.5%-2.5% of Mo, 0.3%-0.8% of Nb, 0.02%-0.05% of RE, 0.1%-0.2% of C and the balance Ni and inevitable impurities; the total content of the impurities is less than or equal to 0.08%, S is less than or equal to 0.005%, and P is less than or equal to 0.005%; the raw materials are subjected to the processes of pretreatment, vacuum melting, atomization powder preparation, base material pretreatment, double-stage spraying, aftertreatment and the like, and the problems that in the prior art, a thermal spraying Ni / Cr alloy coating is poor in hardness at the high temperature, serious in corrosion and low in yield can be effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of metallic materials, specifically relating to a thermally sprayed Ni / Cr alloy coating and its preparation method. Background Technology

[0002] Thermally sprayed Ni / Cr alloy coatings, due to their combination of corrosion resistance and mechanical strength, have been widely used in metallurgical furnace rollers, high-temperature valves, and aero-engine accessories, becoming one of the core materials for surface protection of components operating at temperatures up to 900°C. As industrial equipment develops towards higher parameters and longer lifespans, components must simultaneously withstand the combined effects of high-temperature oxidation, corrosive media erosion, and mechanical wear, placing more stringent demands on the overall performance of coatings. However, existing thermally sprayed Ni / Cr alloy coatings have gradually revealed many key shortcomings in practical applications, severely limiting their service capability under harsh conditions.

[0003] The core problems of existing Ni / Cr alloy coatings are concentrated in three aspects: First, there is an imbalance between high-temperature corrosion resistance and structural stability. Traditional materials are mostly designed with Cr content of 22-27% or 40-75%. The former makes it difficult to form a continuous and dense Cr2O3 protective film, which is easily oxidized at 900℃. After oxidation, the high Cr content leads to increased alloy brittleness and easy coating peeling. Second, it is difficult to balance wear resistance and toughness. Existing technologies mostly add single reinforcing elements such as Ti. Although TiC reinforcing phase can be formed to improve hardness, there is a lack of grain-refining elements to work together, resulting in coarse alloy grains (10-20μm), insufficient coating toughness, and easy cracking under impact load. Third, the oxide film has poor stability. The thermal expansion coefficients of the Cr2O3 film and the substrate are very different, and it is easy to fall off during thermal cycling. Moreover, there are no effective elements to regulate interfacial stress, so long-term protection cannot be achieved.

[0004] To address these issues, the industry has attempted to improve the coating process by adjusting element content, adding single functional elements, or optimizing the spraying process. However, all of these methods have significant drawbacks: adjusting Cr content does not specify a precise range, making it impossible to balance corrosion resistance and brittleness; adding single elements such as Mo and Ti lacks synergistic design, resulting in limited functional synergy; traditional processes are not optimized for multi-element formulations, leading to an 8-12% oxidation loss rate of Cr and Ti during smelting; and single aging processes after spraying can easily cause agglomeration of the reinforcing phase, ultimately resulting in a coating yield of only 60-70%.

[0005] The aforementioned technical bottlenecks directly result in extremely short coating lifespans for components under high-temperature conditions, necessitating frequent downtime for replacement. This not only increases maintenance costs but also impacts production continuity, becoming a key factor restricting the efficient development of industries such as metallurgy and aerospace. Therefore, developing a thermally sprayed Ni / Cr alloy material that achieves a unified multi-objective of "high-temperature corrosion resistance, high wear resistance, high toughness, and high yield" through precise formulation synergy and process adaptation has become an urgent technical challenge for the industry. Its research and application have significant technical value and are of great industrial urgency. Summary of the Invention

[0006] The purpose of this invention is to address the problems of poor hardness, severe corrosion, and low yield of thermally sprayed Ni / Cr alloy coatings at high temperatures in existing technologies, and to provide a novel thermally sprayed Ni / Cr alloy coating and its preparation method. This novel alloy coating material, through formulation design and process optimization, can effectively solve the above problems. To achieve the above objective, the technical solution adopted by this invention to solve its technical problems is as follows: This invention provides a thermally sprayed Ni / Cr alloy coating, comprising the following powder raw materials in parts by weight: Cr 44-46%, Ti 0.5-1.0%, Mo 1.5-2.5%, Nb 0.3-0.8%, RE 0.02-0.05%, C 0.1-0.2%, with the balance being Ni and unavoidable impurities; the total content of the impurities is ≤0.08%, and wherein S≤0.005% and P≤0.005%.

[0007] Furthermore, the weight ratio of Cr to Mo is (17.6-30):1.

[0008] Furthermore, the weight ratio of Ti to Nb is 1:(0.5-1.2).

[0009] Furthermore, the RE is La and / or Ce.

[0010] Another object of the present invention is to provide a method for preparing a thermally sprayed Ni / Cr alloy coating, comprising the following steps: S1, Raw material pretreatment: Select Ni powder, Cr powder, Ti powder, Mo powder, Nb powder, RE powder, and C powder with a purity ≥99.95%. Among them, Cr powder and Mo powder are activated in a vacuum environment at 300℃ for 1.5h. Then, mix all raw materials in proportion and premix using a double planetary ball mill. S2, Vacuum Melting: Put the raw materials from S1 into a vacuum induction furnace with a vacuum degree ≤5Pa; raise the room temperature to 1200℃ and hold for 20-30 minutes; raise the temperature from 1200℃ to 1600-1680℃ and hold for 30-60 minutes; during this period, use electromagnetic stirring at a frequency of 3500-5000Hz and pass Ar gas to disturb the alloy liquid; S3, Atomization Powder Making: The alloy liquid in S2 is introduced into the atomization can through a nozzle with a diameter of 3-6mm, and Ar atomization is used; S4, Powder Classification and Drying: Powders of 15-75μm were screened by three-stage airflow classification and then dried in a vacuum environment at 150℃ for 1 hour, with the moisture content controlled to be ≤0.05%; S5, Substrate Pretreatment and Two-Stage Spraying: The substrate to be sprayed is sandblasted with 80-120 mesh alumina sand, then activated with 5-8% dilute hydrochloric acid for 10-15 minutes, followed by ultrasonic cleaning with ethanol; induction heating is used to 280-320℃ and held for 20-30 minutes, first plasma spraying of Ni-10Cr transition layer; then supersonic flame spraying or vacuum plasma spraying is used to form the working layer of powder in S4. S6, Post-treatment: The coating obtained in S5 is subjected to segmented aging treatment: Ar gas is purged at 5-8 L / min for protection, the first stage is held at 350-380℃ for 1.5 h; the second stage is held at 420-450℃ for 1 h; laser shock wave treatment is used to obtain thermally sprayed Ni / Cr alloy coating.

[0011] Furthermore, The powder prepared in S3 has a particle size of 15-75 μm; wherein, the proportion of powder with a particle size of 15-50 μm is ≥70%, the proportion of powder with a particle size of 50-75 μm is ≤30%, and the sphericity of the powder is ≥95%.

[0012] Furthermore, In S5, the parameters for supersonic flame spraying are: kerosene flow rate 25-32 L / h, oxygen flow rate 850-1050 L / h, powder feeding rate 50-80 g / min, and spraying distance 200-350 mm; the parameters for vacuum plasma spraying are: vacuum degree 10-20 Pa, spraying power 45-50 kW, argon flow rate 45-50 L / min, powder feeding rate 40-60 g / min, and spraying distance 100-120 mm.

[0013] Another object of the present invention is to provide the coating suitable for surface protection of parts that need to withstand long-term high-temperature oxidation, corrosion and wear at 900°C.

[0014] The present invention has the following beneficial effects: (1) The present invention provides a thermal spray Ni / Cr alloy coating, wherein Ni is the matrix and Cr is the core anti-high temperature corrosion element in the alloy composition, which can form a continuous and dense Cr2O3 main protective film; Mo is the auxiliary anti-corrosion element, which can synergistically form a "Cr2O3-MoO3" composite oxide film with Cr, thereby synergistically improving the density of the oxide film and improving the high temperature corrosion resistance; at the same time, Cr and Mo can also form carbides with C, and hard phases such as chromium carbide are dispersed in the solid solution strengthened matrix, thereby improving high temperature strength and other properties.

[0015] (2) The present invention provides a thermally sprayed Ni / Cr alloy coating, wherein a certain amount of Ti and Nb elements are added to the alloy composition. Among them, Ti is a dispersion strengthening core that can generate TiC strengthening phase in situ; Nb is a grain refinement and synergistic strengthening element that can refine the alloy grain to 3-8μm and form NbTiC composite strengthening phase with Ti; at the same time, this ratio ensures that the strengthening effect of Ti and the toughness-enhancing effect of Nb are balanced, and the hardness and toughness are improved simultaneously.

[0016] (3) The present invention provides a thermal spray Ni / Cr alloy coating, in which a certain amount of rare earth elements are added to the alloy. These rare earth elements are oxide film stabilizing elements. The addition of trace amounts can be adsorbed at the Cr2O3 film-substrate interface, inhibiting oxide film peeling and improving high temperature corrosion resistance.

[0017] (4) This invention provides a process for preparing a thermally sprayed Ni / Cr alloy coating. First, vacuum melting is performed with segmented temperature control to avoid oxidation and burn-off of Cr, Ti, and Mo, ensuring the accurate implementation of the element ratios designed in the formulation. Second, segmented aging is used to avoid agglomeration of the reinforcing phase. Laser shock wave compression of pores ensures uniform distribution of the reinforcing phases formed by the formulation elements, fully leveraging their synergistic effect. Third, a transition layer is used to adapt to the thermal expansion difference between the formulation and the substrate, preventing the coating from cracking due to stress and ensuring stable adhesion of the protective layer formed by the formulation. The various operation steps in the process work together to improve the yield and the high-temperature resistance of the thermally sprayed Ni / Cr alloy coating. Detailed Implementation

[0018] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0019] The purpose of this invention is to develop a thermally sprayable Ni / Cr alloy coating to solve the problems of poor hardness, severe corrosion, and low yield of existing Ni / Cr alloy coatings at high temperatures. The approach is as follows: considering that the core problem of existing coatings lies in the lack of synergistic design of element ratios and the fragmentation of performance due to the incompatibility of processes with multi-element systems, this invention fundamentally solves the problem through "precise formulation synergy + process adaptation closed loop." It employs a precise ratio of Cr (44-46%) and Mo (1.5-2.5%) to form a "Cr2O3-MoO3" composite oxide film, with Ti (0.5-1.0%) and Nb (0.3-0.8%) synergistically refining the grain size to 3-8 μm, and RE (0.02-0.05%) stabilizing the oxide film interface; simultaneously... By employing processes such as raw material activation, vacuum melting with segmented temperature control, segmented aging, and laser shock wave treatment, element loss is reduced, ordered precipitation of strengthening phases is achieved, and porosity is decreased. Synergistic effects of Cr-Mo corrosion resistance and Ti-Nb strengthening are achieved through formulation synergy. A closed-loop formulation and process system ensures precise proportioning through raw material activation, amplifies the strengthening phase effect through segmented aging, and further densifies through laser treatment, resulting in a synergistic improvement in multiple properties: corrosion resistance, wear resistance, high toughness, and high yield. It achieves Level 1 complete oxidation resistance at 900℃ and exhibits excellent room-temperature and high-temperature hardness, high wear resistance, and high yield. Examples of this invention are as follows: This invention provides a thermally sprayed Ni / Cr alloy coating, comprising the following powder raw materials in parts by weight: Cr 44-46%, Ti 0.5-1.0%, Mo 1.5-2.5%, Nb 0.3-0.8%, RE 0.02-0.05%, C 0.1-0.2%, with the balance being Ni and unavoidable impurities; the total impurity content is ≤0.08%, and S≤0.005% and P≤0.005%.

[0020] The weight ratio of Cr to Mo is (17.6-30):1.

[0021] Solving the problem of "high temperature corrosion resistance foundation": Cr is the core high temperature corrosion resistant element, and its content of 44-46% ensures the formation of a continuous and dense Cr2O3 main protective film at 900℃; Mo is the auxiliary corrosion resistant element, and its content of 1.5-2.5% can work together with Cr to form a "Cr2O3-MoO3" composite oxide film. MoO3 can fill the microcracks in the Cr2O3 film, and the alloy matrix toughness will not decrease due to excessive Mo.

[0022] The weight ratio of Ti to Nb is 1:(0.5-1.2).

[0023] To address the imbalance between hardness and toughness: Ti serves as the dispersion strengthening core, and a content of 0.5-1.0% can generate a TiC strengthening phase with a particle size ≤5μm in situ; Nb is a grain refinement and synergistic strengthening element, and a content of 0.3-0.8% can refine the alloy grain from the traditional 10-20μm to 3-8μm, while simultaneously forming an NbTiC composite strengthening phase with Ti. This ratio ensures a balance between the strengthening effect of Ti and the toughness-enhancing effect of Nb, avoiding coating embrittlement caused by the addition of Ti alone.

[0024] The RE is La and / or Ce.

[0025] To address the issue of "poor oxide film stability": RE is an oxide film stabilizing element. A trace addition of 0.02-0.05% can adsorb onto the Cr2O3 film-substrate interface, reducing the difference in thermal expansion coefficients and inhibiting oxide film peeling. This ratio can prevent excessive La / Ce from forming rare earth oxide inclusions or excessive consumption of Cr elements, which would affect the formation of the Cr2O3 film.

[0026] Impurity control (total ≤0.08%, S≤0.005%, P≤0.005%): avoids thermal brittleness defects and ensures the basic performance of the formulation.

[0027] Another objective of this invention is to provide a method for preparing a thermally sprayed Ni / Cr alloy coating, comprising the following steps: S1, Raw material pretreatment: Select Ni powder, Cr powder, Ti powder, Mo powder, Nb powder, RE powder, and C powder with a purity ≥99.95%. Among them, Cr powder and Mo powder are first activated in a vacuum environment at 300℃ for 1.5h. Then, mix all raw materials in proportion and premix them using a double planetary ball mill (speed 200-300r / min, time 1-2h, ball-to-material ratio 5:1, medium is anhydrous ethanol). S2, Vacuum Melting: The raw materials from S1 are put into a vacuum induction furnace with a vacuum degree ≤5Pa; the room temperature is raised to 1200℃ (heating rate 8-10℃ / min, with Ar gas introduced at 5-10L / min for dynamic degassing) and held for 20-30min; then the temperature is raised from 1200℃ to 1600-1680℃ (heating rate 5℃ / min) and held for 30-60min; during this period, the alloy liquid is stirred electromagnetically at a frequency of 3500-5000Hz and Ar gas is introduced to disturb the alloy liquid. S3, Atomization Powder Making: The alloy liquid in S2 is introduced into the atomizing tank through a nozzle with a diameter of 3-6mm, and Ar atomization is used (pressure 3.5-5.0MPa, atomization cone angle 55-75°). S4, Powder Classification and Drying: Powders of 15-75μm were screened by three-stage airflow classification and then dried in a vacuum environment at 150℃ for 1 hour, with the moisture content controlled to ≤0.05%; S5, Substrate Pretreatment and Two-Stage Spraying: The substrate to be sprayed (carbon steel, alloy steel, or nickel-based alloy) is sandblasted with 80-120 mesh alumina sand (roughness Ra=6-12μm), then activated with 5-8% dilute hydrochloric acid for 10-15 min, followed by ultrasonic cleaning with ethanol; induction heating is used to 280-320℃ and held for 20-30 min, first plasma spraying a Ni-10Cr transition layer (thickness 50-80μm); then supersonic flame spraying or vacuum plasma spraying is used to form a working layer (thickness 0.6-1.8mm) of the powder in S4. S6, Post-processing: The coating obtained in S5 is subjected to segmented aging treatment: Ar gas is purged at 5-8 L / min for protection, the first stage is held at 350-380℃ for 1.5 h; the second stage is held at 420-450℃ for 1 h; laser shock wave treatment is used (power 100-200W, scanning speed 5-10 mm / s) to obtain thermally sprayed Ni / Cr alloy coating.

[0028] The powder prepared in S3 has a particle size of 15-75 μm; wherein, the proportion of powder with a particle size of 15-50 μm is ≥70%, the proportion of powder with a particle size of 50-75 μm is ≤30%, and the sphericity of the powder is ≥95%.

[0029] In S5, the parameters for supersonic flame spraying are: kerosene flow rate 25-32 L / h, oxygen flow rate 850-1050 L / h, powder feeding rate 50-80 g / min, and spraying distance 200-350 mm; the parameters for vacuum plasma spraying are: vacuum degree 10-20 Pa, spraying power 45-50 kW, argon flow rate 45-50 L / min, powder feeding rate 40-60 g / min, and spraying distance 100-120 mm.

[0030] Another objective of this invention is to provide the coating suitable for surface protection of components that need to withstand long-term high-temperature oxidation, corrosion and wear at 900°C.

[0031] To further understand the present invention, the thermal spraying Ni / Cr alloy coating provided by the present invention will be described in detail below with reference to specific embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0032] Example 1 A thermally sprayed Ni / Cr alloy coating comprises the following powder raw materials in parts by weight: The composition is 45% Cr, 0.7% Ti, 2.0% Mo, 0.6% Nb, 0.035% RE, and 0.17% C, with the balance being Ni and unavoidable impurities; the total content of the impurities is ≤0.08%, and S≤0.005% and P≤0.005%.

[0033] The weight ratio of Cr to Mo is 22.5:1.

[0034] The weight ratio of Ti to Nb is 1:0.86.

[0035] The RE is La and Ce added at a mass ratio of 1:2.

[0036] A method for preparing a thermally sprayed Ni / Cr alloy coating includes the following steps: S1, Raw material pretreatment: Select Ni powder, Cr powder, Ti powder, Mo powder, Nb powder, RE powder, and C powder with a purity ≥99.95%. Among them, Cr powder and Mo powder are first activated in a vacuum environment at 300℃ for 1.5h. Then, mix all raw materials in proportion and premix them using a double planetary ball mill (speed 250r / min, time 1.5h, ball-to-material ratio 5:1, medium is anhydrous ethanol). S2, Vacuum Melting: The raw materials in S1 are put into a vacuum induction furnace with a vacuum degree ≤5Pa; the room temperature is raised to 1200℃ (heating rate 10℃ / min, with Ar gas being introduced at 8L / min for dynamic degassing) and held for 25min; then the temperature is raised from 1200℃ to 1640℃ (heating rate 5℃ / min) and held for 40min; during this period, the alloy liquid is stirred electromagnetically at a frequency of 4500Hz and Ar gas is introduced to disturb the alloy liquid. S3, Atomization Powder Making: The alloy liquid in S2 is introduced into the atomization tank through a 5mm diameter nozzle and atomized using Ar (pressure 4.5MPa, atomization cone angle 65°). S4, Powder Classification and Drying: Powders of 15-75μm were screened by three-stage airflow classification and then dried in a vacuum environment at 150℃ for 1 hour, with the moisture content controlled to ≤0.05%; S5, Substrate Pretreatment and Two-Stage Spraying: The substrate (nickel-based alloy) to be sprayed is sandblasted with 100-mesh alumina sand (roughness Ra=10μm), then activated with 8% dilute hydrochloric acid for 10 min and ultrasonically cleaned with ethanol; induction heating is used to 300℃ and held for 25 min, first plasma spraying of Ni-10Cr transition layer (thickness 60μm); then supersonic flame spraying is used to form the working layer (thickness 1.2mm) of powder in S4. S6, Post-processing: The coating obtained in S5 is subjected to segmented aging treatment: Ar gas is purged at 6L / min for protection, the first stage is held at 360℃ for 1.5h; the second stage is held at 435℃ for 1h; laser shock wave treatment (power 150W, scanning speed 8mm / s) is used to obtain thermally sprayed Ni / Cr alloy coating.

[0037] The powder prepared in S3 has a particle size of 15-75 μm; wherein, the powder with a particle size of 15-50 μm accounts for 70%, the powder with a particle size of 50-75 μm accounts for 30%, and the sphericity of the powder is ≥95%.

[0038] In S5, the parameters for supersonic flame spraying are: kerosene flow rate 28L / h, oxygen flow rate 950L / h, powder feeding rate 65g / min, and spraying distance 290mm.

[0039] Example 2 A thermally sprayed Ni / Cr alloy coating comprises the following powder raw materials in parts by weight: The composition is Cr 44%, Ti 1.0%, Mo 1.95%, Nb 0.8%, RE 0.02%, C 0.2%, with the balance being Ni and unavoidable impurities; the total content of the impurities is ≤0.08%, and S≤0.005% and P≤0.005%.

[0040] The weight ratio of Cr to Mo is 22.5:1.

[0041] The weight ratio of Ti to Nb is 1:0.86.

[0042] The RE is La and Ce added at a mass ratio of 1:2.

[0043] A method for preparing a thermally sprayed Ni / Cr alloy coating includes the following steps: S1, Raw material pretreatment: Select Ni powder, Cr powder, Ti powder, Mo powder, Nb powder, RE powder, and C powder with a purity ≥99.95%. Among them, Cr powder and Mo powder are first activated in a vacuum environment at 300℃ for 1.5h. Then, mix all raw materials in proportion and premix them using a double planetary ball mill (speed 250r / min, time 1.5h, ball-to-material ratio 5:1, medium is anhydrous ethanol). S2, Vacuum Melting: The raw materials in S1 are put into a vacuum induction furnace with a vacuum degree ≤5Pa; the room temperature is raised to 1200℃ (heating rate 10℃ / min, with Ar gas introduced at 8L / min for dynamic degassing) and held for 20min; then the temperature is raised from 1200℃ to 1680℃ (heating rate 5℃ / min) and held for 30min; during this period, the alloy liquid is stirred electromagnetically at a frequency of 3500Hz and Ar gas is introduced to disturb the alloy liquid. S3, Atomization Powder Making: The alloy liquid in S2 is introduced into the atomization tank through a 5mm diameter nozzle and atomized using Ar (pressure 4.5MPa, atomization cone angle 65°). S4, Powder Classification and Drying: Powders of 15-75μm were screened by three-stage airflow classification and then dried in a vacuum environment at 150℃ for 1 hour, with the moisture content controlled to ≤0.05%; S5, Substrate Pretreatment and Two-Stage Spraying: The substrate (nickel-based alloy) to be sprayed is sandblasted with 100-mesh alumina sand (roughness Ra=10μm), then activated with 8% dilute hydrochloric acid for 10 min and ultrasonically cleaned with ethanol; induction heating is used to 280℃ and held for 30 min, first plasma spraying of Ni-10Cr transition layer (thickness 60μm); then supersonic flame spraying is used to form the working layer (thickness 1.2mm) of powder in S4. S6, Post-processing: The coating obtained in S5 is subjected to segmented aging treatment: Ar gas is purged at 6L / min for protection, the first stage is held at 350℃ for 1.5h; the second stage is held at 420℃ for 1h; laser shock wave treatment (power 150W, scanning speed 8mm / s) is used to obtain thermally sprayed Ni / Cr alloy coating.

[0044] The powder prepared in S3 has a particle size of 15-75 μm; wherein, the powder with a particle size of 15-50 μm accounts for 80%, the powder with a particle size of 50-75 μm accounts for 20%, and the sphericity of the powder is ≥95%.

[0045] In S5, the parameters for supersonic flame spraying are: kerosene flow rate 28L / h, oxygen flow rate 950L / h, powder feeding rate 65g / min, and spraying distance 290mm.

[0046] Example 3 A thermally sprayed Ni / Cr alloy coating comprises the following powder raw materials in parts by weight: The composition is 46% Cr, 0.5% Ti, 2.04% Mo, 0.43% Nb, 0.05% RE, and 0.1% C, with the balance being Ni and unavoidable impurities; the total content of the impurities is ≤0.08%, and S≤0.005% and P≤0.005%.

[0047] The weight ratio of Cr to Mo is 22.5:1.

[0048] The weight ratio of Ti to Nb is 1:0.86.

[0049] The RE is La and Ce added at a mass ratio of 1:2.

[0050] A method for preparing a thermally sprayed Ni / Cr alloy coating includes the following steps: S1, Raw material pretreatment: Select Ni powder, Cr powder, Ti powder, Mo powder, Nb powder, RE powder, and C powder with a purity ≥99.95%. Among them, Cr powder and Mo powder are first activated in a vacuum environment at 300℃ for 1.5h. Then, mix all raw materials in proportion and premix them using a double planetary ball mill (speed 250r / min, time 1.5h, ball-to-material ratio 5:1, medium is anhydrous ethanol). S2, Vacuum Melting: The raw materials in S1 are put into a vacuum induction furnace with a vacuum degree ≤5Pa; the room temperature is raised to 1200℃ (heating rate 10℃ / min, with Ar gas introduced at 8L / min for dynamic degassing) and held for 30min; then the temperature is raised from 1200℃ to 1600℃ (heating rate 5℃ / min) and held for 60min; during this period, the alloy liquid is stirred electromagnetically at a frequency of 5000Hz and Ar gas is introduced to disturb it. S3, Atomization Powder Making: The alloy liquid in S2 is introduced into the atomization tank through a 5mm diameter nozzle and atomized using Ar (pressure 4.5MPa, atomization cone angle 65°). S4, Powder Classification and Drying: Powders of 15-75μm were screened by three-stage airflow classification and then dried in a vacuum environment at 150℃ for 1 hour, with the moisture content controlled to ≤0.05%; S5, Substrate Pretreatment and Two-Stage Spraying: The substrate (nickel-based alloy) to be sprayed is sandblasted with 100-mesh alumina sand (roughness Ra=10μm), then activated with 8% dilute hydrochloric acid for 10 min and ultrasonically cleaned with ethanol; induction heating is used to 320℃ and held for 20 min, first plasma spraying of Ni-10Cr transition layer (thickness 60μm); then vacuum plasma spraying is used to form working layer (thickness 1.2mm) of powder in S4. S6, Post-processing: The coating obtained in S5 is subjected to segmented aging treatment: Ar gas is purged at 6L / min for protection, the first stage is held at 380℃ for 1.5h; the second stage is held at 450℃ for 1h; laser shock wave treatment (power 150W, scanning speed 8mm / s) is used to obtain thermally sprayed Ni / Cr alloy coating.

[0051] The powder prepared in S3 has a particle size of 15-75 μm; wherein, the powder with a particle size of 15-50 μm accounts for 70%, the powder with a particle size of 50-75 μm accounts for 30%, and the sphericity of the powder is ≥95%.

[0052] In S5, the parameters for vacuum plasma spraying are: vacuum degree 15Pa, spraying power 50kW, argon flow rate 50L / min, powder feeding rate 50g / min, and spraying distance 120mm.

[0053] Example 4 Everything else is the same as in Example 1, except that: A thermally sprayed Ni / Cr alloy coating comprises the following powder raw materials in parts by weight: The composition is 45% Cr, 0.7% Ti, 2.5% Mo, 0.6% Nb, 0.035% RE, and 0.17% C, with the balance being Ni and unavoidable impurities; the total content of the impurities is ≤0.08%, and S≤0.005% and P≤0.005%.

[0054] The weight ratio of Cr to Mo is 18:1.

[0055] Example 5 Everything else is the same as in Example 1, except that: A thermally sprayed Ni / Cr alloy coating comprises the following powder raw materials in parts by weight: Cr 45%, Ti 0.7%, Mo 1.5%, Nb 0.6%, RE 0.035%, with the balance being Ni and unavoidable impurities; the total content of the impurities is ≤0.08%, and S≤0.005% and P≤0.005%.

[0056] The weight ratio of Cr to Mo is 30:1.

[0057] Example 6 Everything else is the same as in Example 1, except that: A thermally sprayed Ni / Cr alloy coating comprises the following powder raw materials in parts by weight: The composition is 45% Cr, 0.7% Ti, 2.0% Mo, 0.35% Nb, 0.035% RE, and 0.17% C, with the balance being Ni and unavoidable impurities; the total impurity content is ≤0.08%, and S≤0.005% and P≤0.005%.

[0058] The weight ratio of Ti to Nb is 1:0.5.

[0059] Example 7 Everything else is the same as in Example 1, except that: A thermally sprayed Ni / Cr alloy coating comprises the following powder raw materials in parts by weight: The composition is 45% Cr, 0.7% Ti, 2.0% Mo, 0.8% Nb, 0.035% RE, and 0.17% C, with the balance being Ni and unavoidable impurities; the total content of the impurities is ≤0.08%, and S≤0.005% and P≤0.005%.

[0060] The weight ratio of Ti to Nb is 1:1.14.

[0061] Example 8 Everything else is the same as in Example 1, except that: In a thermal spraying Ni / Cr alloy coating formulation, RE is Ce.

[0062] The following comparative examples are all compared with Example 1: Comparative Example 1 Everything else is the same as in Example 1, except that: A thermally sprayed Ni / Cr alloy coating comprises the following powder raw materials in parts by weight: The composition is 45% Cr, 0.7% Ti, 1.0% Mo, 0.6% Nb, 0.035% RE, and 0.17% C, with the balance being Ni and unavoidable impurities; the total content of the impurities is ≤0.08%, and S≤0.005% and P≤0.005%.

[0063] The weight ratio of Cr to Mo is 45:1.

[0064] Comparative Example 2 Everything else is the same as in Example 1, except that: A thermally sprayed Ni / Cr alloy coating comprises the following powder raw materials in parts by weight: The composition is 45% Cr, 0.7% Ti, 2.0% Mo, 0.3% Nb, 0.035% RE, and 0.17% C, with the balance being Ni and unavoidable impurities; the total content of the impurities is ≤0.08%, and S≤0.005% and P≤0.005%.

[0065] The weight ratio of Ti to Nb is 1:0.43.

[0066] Implement Comparative Example 3 Everything else is the same as in Example 1, except that: A thermally sprayed Ni / Cr alloy coating comprises the following powder raw materials in parts by weight: The composition is 45% Cr, 0.7% Ti, 2.0% Mo, 0.9% Nb, 0.035% RE, and 0.17% C, with the balance being Ni and unavoidable impurities; the total content of the impurities is ≤0.08%, and S≤0.005% and P≤0.005%.

[0067] The weight ratio of Ti to Nb is 1:1.29.

[0068] Comparative Example 4 Everything else is the same as in Example 1, except that: In a thermal spraying Ni / Cr alloy coating formulation, the amount of RE added is 0.01%.

[0069] Comparative Example 5 Everything else is the same as in Example 1, except that: In a thermal spray Ni / Cr alloy coating formulation, the amount of RE added is 0.06%.

[0070] Comparative Example 6 Everything else is the same as in Example 1, except that: A method for preparing a thermally sprayed Ni / Cr alloy coating, wherein step S2 specifically comprises: S2, Vacuum Melting: The raw materials in S1 are put into a vacuum induction furnace with a vacuum degree ≤5Pa; the room temperature is raised to 1640℃ (where the heating rate from room temperature to 1200℃ is 10℃ / min, and Ar gas is simultaneously introduced at 8L / min for dynamic degassing; the heating rate from 1200℃ to 1640℃ is 5℃ / min), and held for 40min; during this period, the alloy liquid is stirred electromagnetically at a frequency of 4500Hz and Ar gas is introduced to disturb it.

[0071] Comparative Example 7 Everything else is the same as in Example 1, except that: A method for preparing a thermally sprayed Ni / Cr alloy coating, wherein step S6 specifically comprises: S6, Post-treatment: The coating obtained in S5 is subjected to aging treatment: Ar gas is purged at 6L / min for protection, and the temperature is maintained at 435℃ for 2.5h; Laser shock wave treatment (power 150W, scanning speed 8mm / s) is used to obtain thermally sprayed Ni / Cr alloy coating.

[0072] Implemented Comparative Example 8 Everything else is the same as in Example 1, except that: A method for preparing a thermally sprayed Ni / Cr alloy coating, wherein step S6 specifically comprises: S6, Post-treatment: The coating obtained in S5 is subjected to segmented aging treatment: Ar gas is purged at 6L / min for protection, the first stage is held at 360℃ for 1.5h; the second stage is held at 435℃ for 1h, to obtain the thermally sprayed Ni / Cr alloy coating.

[0073] Comparative Example 9 Everything else is the same as in Example 1, except that: A method for preparing a thermally sprayed Ni / Cr alloy coating, wherein step S5 specifically comprises: S5, Substrate Pretreatment and Spraying: The substrate (nickel-based alloy) to be sprayed is sandblasted with 100-mesh alumina sand (roughness Ra=10μm), then activated with 8% dilute hydrochloric acid for 10 min and ultrasonically cleaned with ethanol; induction heating is used to 300℃ and held for 25 min, and then supersonic flame is used to spray the powder in S4 to form a working layer (thickness 1.2mm).

[0074] Implement Comparative Example 10 Everything else is the same as in Example 1, except that: A method for preparing a thermally sprayed Ni / Cr alloy coating. The powder prepared in S3 has a particle size of 15-75 μm; wherein, the powder with a particle size of 15-50 μm accounts for 60%, the powder with a particle size of 50-75 μm accounts for 40%, and the sphericity of the powder is ≥95%.

[0075] The physical properties of the thermally sprayed Ni / Cr alloy coatings prepared in the embodiments and comparative examples of the present invention were measured respectively, and the results are shown in Table 1.

[0076] Table 1 Physical test performance of each embodiment Example Yield (%) High-temperature oxidation resistance (grade) Corrosion resistance Hardness (HV) at room temperature / 900℃ Wear resistance (coefficient of friction) Example 1 95.6 1 No pitting corrosion, crevice corrosion 943 / 734 0.42 / 0.26 Example 2 93.2 1 No pitting corrosion, crevice corrosion 903 / 708 0.44 / 0.29 Example 3 95.1 1 No pitting corrosion, crevice corrosion 917 / 711 0.42 / 0.26 Example 4 95.3 1 No pitting corrosion, crevice corrosion 939 / 735 0.42 / 0.27 Example 5 95.0 1 No pitting corrosion, crevice corrosion 882 / 670 0.46 / 0.30 Example 6 94.8 1 No pitting corrosion, crevice corrosion 924 / 703 0.49 / 0.34 Example 7 94.5 1 No pitting corrosion, crevice corrosion 853 / 632 0.46 / 0.32 Example 8 95.4 1 No pitting corrosion, crevice corrosion 939 / 707 0.45 / 0.33 Comparative Example 1 95.2 2 pitting 815 / 606 0.43 / 0.45 Comparative Example 2 94.4 2 No pitting corrosion, crevice corrosion 900 / 609 0.49 / 0.43 Implement Comparative Example 3 95.0 2 No pitting corrosion, crevice corrosion 746 / 515 0.48 / 0.41 Comparative Example 4 95.5 2 Pitting corrosion, crevice corrosion 905 / 634 0.53 / 0.57 Comparative Example 5 95.1 2 pitting 948 / 680 0.51 / 0.55 Comparative Example 6 86.3 3 Pitting corrosion, crevice corrosion 863 / 657 0.50 / 0.48 Comparative Example 7 94.7 1 No pitting corrosion, crevice corrosion 771 / 539 0.55 / 0.52 Implemented Comparative Example 8 94.9 3 Pitting corrosion, crevice corrosion 934 / 691 0.53 / 0.55 Comparative Example 9 88.6 1 No pitting corrosion, crevice corrosion 940 / 728 0.47 / 0.28 Implement Comparative Example 10 87.8 1 pitting 881 / 682 0.49 / 0.47 As can be observed from Examples 1-8, the thermally sprayed Ni / Cr alloy coating of the present invention has excellent yield, physical properties and high temperature resistance.

[0077] As can be observed from Example 1 and Comparative Examples 1-4, the addition of an appropriate amount of Mo in the thermally sprayed Ni / Cr alloy coating of the present invention achieves solid solution strengthening, improves the density of the oxide film, and thus improves corrosion resistance; the appropriate Ti and Nb ratio balances hardness and toughness, and improves high-temperature hardness; the appropriate RE stabilizes the oxide film interface and improves wear resistance stability.

[0078] As can be observed from Example 1 and Comparative Examples 6-10, in the preparation process of the thermally sprayed Ni / Cr alloy coating in this invention, the segmented temperature control of vacuum melting ensures the accurate implementation of the element ratios designed in the formula, improving the yield and physical properties; segmented aging can orderly precipitate fine strengthening phases, avoid agglomeration, and improve hardness stability; laser shock wave compresses pores, improves density, and enhances corrosion resistance and wear resistance; the transition layer improves the coating bonding strength and can also improve the yield; atomized powder with appropriate particle size improves spraying efficiency and yield while also improving coating density, thereby improving physical properties.

[0079] In summary, the thermal sprayed Ni / Cr alloy coating of the present invention, through the synergistic effect of optimized formulation design and process preparation, exhibits excellent yield, physical properties, and high-temperature resistance.

[0080] The testing method is as follows: (1) Yield: The comprehensive yield is calculated in two steps: First, the powder utilization rate is calculated as the mass of qualified particle size powder / the total mass of raw materials; then, the spray deposition rate is calculated as the actual coating mass / the total mass of sprayed powder; finally, the comprehensive yield is calculated as the powder utilization rate × the spray deposition rate.

[0081] (2) Resistance to high temperature oxidation: The test was conducted in accordance with GB / T 13303-2008 "Determination of oxidation resistance of steel". The test time was 1000h.

[0082] (3) Corrosion resistance: Refer to GB / T10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test". Immerse in a 5% NaCl + 1% H2S mixed solution for 720h.

[0083] (4) Hardness: Refer to GB / T4340.1-2009 "Metallic materials Vickers hardness test - Part 1: Test method". Load 0.3kg, loading time 10s.

[0084] (5) Wear resistance: The friction and wear test was conducted using the German IV high-temperature reciprocating friction and wear tester. The coating was a constant-moving upper sample, and the grinding part was a stationary lower sample. The test load was 100N, the frequency was 50Hz, the stroke was 2mm, the wear time was 30min, and the temperatures were room temperature and 900℃. The grinding part was ceramic.

[0085] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A thermally sprayed Ni / Cr alloy coating, characterized in that: The powder raw materials include the following parts by weight: Cr 44-46%, Ti 0.5-1.0%, Mo 1.5-2.5%, Nb 0.3-0.8%, RE 0.02-0.05%, C 0.1-0.2%, with the balance being Ni and unavoidable impurities; the total content of the impurities is ≤0.08%, and wherein S≤0.005% and P≤0.005%.

2. The thermally sprayed Ni / Cr alloy coating according to claim 1, characterized in that: The weight ratio of Cr to Mo is (17.6-30):

1.

3. The thermally sprayed Ni / Cr alloy coating according to claim 1, characterized in that: The weight ratio of Ti to Nb is 1:(0.5-1.2).

4. The thermally sprayed Ni / Cr alloy coating according to claim 1, characterized in that: The RE is La and / or Ce.

5. A method for preparing a thermally sprayed Ni / Cr alloy coating, characterized in that: Includes the following steps: S1, Raw material pretreatment: Select Ni powder, Cr powder, Ti powder, Mo powder, Nb powder, RE powder, and C powder with a purity ≥99.95%. Among them, Cr powder and Mo powder are activated in a vacuum environment at 300℃ for 1.5h. Then, mix all raw materials in proportion and premix using a double planetary ball mill. S2, Vacuum Melting: Put the raw materials from S1 into a vacuum induction furnace with a vacuum degree ≤5Pa; raise the room temperature to 1200℃ and hold for 20-30 minutes; raise the temperature from 1200℃ to 1600-1680℃ and hold for 30-60 minutes; during this period, use electromagnetic stirring at a frequency of 3500-5000Hz and pass Ar gas to disturb the alloy liquid; S3, Atomization Powder Making: The alloy liquid in S2 is introduced into the atomization can through a nozzle with a diameter of 3-6mm, and Ar atomization is used; S4, Powder Classification and Drying: Powders of 15-75μm were screened by three-stage airflow classification and then dried in a vacuum environment at 150℃ for 1 hour, with the moisture content controlled to be ≤0.05%; S5, Substrate Pretreatment and Two-Stage Spraying: The substrate to be sprayed is sandblasted with 80-120 mesh alumina sand, then activated with 5-8% dilute hydrochloric acid for 10-15 minutes, followed by ultrasonic cleaning with ethanol; induction heating is used to 280-320℃ and held for 20-30 minutes, first plasma spraying of Ni-10Cr transition layer; then supersonic flame spraying or vacuum plasma spraying is used to form the working layer of powder in S4. S6, Post-treatment: The coating obtained in S5 is subjected to segmented aging treatment: Ar gas is purged at 5-8 L / min for protection, the first stage is held at 350-380℃ for 1.5 h; the second stage is held at 420-450℃ for 1 h; laser shock wave treatment is used to obtain thermally sprayed Ni / Cr alloy coating.

6. The method for preparing a thermally sprayed Ni / Cr alloy coating according to claim 5, characterized in that: The powder prepared in S3 has a particle size of 15-75 μm; wherein, the proportion of powder with a particle size of 15-50 μm is ≥70%, the proportion of powder with a particle size of 50-75 μm is ≤30%, and the sphericity of the powder is ≥95%.

7. The method for preparing a thermally sprayed Ni / Cr alloy coating according to claim 5, characterized in that: In S5, the parameters for supersonic flame spraying are: kerosene flow rate 25-32 L / h, oxygen flow rate 850-1050 L / h, powder feeding rate 50-80 g / min, and spraying distance 200-350 mm; the parameters for vacuum plasma spraying are: vacuum degree 10-20 Pa, spraying power 45-50 kW, argon flow rate 45-50 L / min, powder feeding rate 40-60 g / min, and spraying distance 100-120 mm.

8. The method for preparing a thermally sprayed Ni / Cr alloy coating according to claim 1, characterized in that: The coating is suitable for surface protection of parts that need to withstand long-term high-temperature oxidation, corrosion and wear at 900℃.