Nickel-based self-fluxing alloy powder and preparation method and application thereof

Abstract

The invention discloses nickel-based self-fluxing alloy powder and a preparation method and application thereof, and belongs to the technical field of metal surface modification. The nickel-based self-fluxing alloy powder comprises the following raw materials in percentage by mass: 50%-75% of Ni, 1.0%-5% of B, 2.0%-5.0% of Si, 15%-25% of Cr, 2.0%-7.0% of Mo, 1.0%-10.0% of W, 0.1%-10% of Cu, 0.5%-5.0% of Ta, 0.5%-5.0% of Nb, 0.3%-5.0% of V and 1.0%-10% of Co. The preparation method specifically comprises the following steps: (1) weighing the raw materials; and (2) smelting, atomizing and crushing, cooling, dehydrating, drying and screening. The thermodynamic property of the nickel-based self-fluxing alloy powder is adjusted, so that the nickel-based self-fluxing alloy powder can be formed on a martensitic stainless steel base material, the protection effect is achieved, and the nickel-based self-fluxing alloy powder is particularly suitable for surface strengthening treatment of mechanical parts (such as hammerheads and ball cores) with strict requirements for coating bonding strength, wear resistance and cracking resistance.

Description

Technical Field

[0001] This invention relates to the field of metal surface modification technology, and more specifically to a nickel-based self-fluxing alloy powder, its preparation method, and its application. Background Technology

[0002] Martensitic stainless steel refers to stainless steel whose mechanical properties can be adjusted through heat treatment; simply put, it is a type of hardenable stainless steel. Typical grades are Cr13 type, such as 2Cr13, 3Cr13, and 4Cr13. It has high hardness after quenching, and different tempering temperatures result in different strength and toughness combinations. It is mainly used in steam turbine blades, tableware, and surgical instruments. Based on differences in chemical composition, martensitic stainless steel can be divided into martensitic chromium steel and martensitic chromium-nickel steel. Based on differences in microstructure and strengthening mechanism, it can also be divided into martensitic stainless steel, martensitic and semi-austenitic (or semi-martensitic) precipitation-hardening stainless steel, and martensitic aging stainless steel, etc.

[0003] Martensitic stainless steel possesses excellent mechanical strength, corrosion resistance, and machinability, making it widely used in the manufacture of key components in machinery manufacturing and engineering machinery. To further enhance its surface wear resistance and extend the service life of components, the industry commonly employs supersonic flame spraying technology to prepare a wear-resistant protective coating on its surface. While this process can improve coating density to some extent, it presents the following core problems:

[0004] 1. Limited process optimization: Traditional solutions often focus on adjusting cladding process parameters (such as preheating temperature) or adding a single hard phase (such as SiC or WC). Although this can reduce some macro cracks, it cannot completely eliminate micro cracks and can easily lead to increased coating brittleness. 2. Insufficient bonding strength: The coating prepared by supersonic flame spraying process is mostly mechanically bonded to the substrate, with a bonding strength of about 80MPa. Under complex working conditions (such as impact and vibration), the coating is prone to peeling off. 3. Coating thickness limitation: Due to process limitations, the coating thickness of supersonic flame spraying is usually around 300μm. The greater the thickness, the more severe the stress concentration in the coating.

[0005] Currently, nickel-based self-fluxing alloy coatings are widely used for surface protection of stainless steel substrates due to the simplicity and ease of operation of the flame spraying + cladding process, achieving a metallurgical bond with the substrate. This process relies on the high-temperature heat source of an oxy-acetylene flame to melt alloy powder on the surface of substrates such as martensitic stainless steel. The specific process can be summarized as follows: First, the surface of the martensitic stainless steel part substrate is sandblasted to improve the adhesion between the coating and the substrate; then, the oxy-acetylene flame parameters are adjusted according to the coating thickness requirements, selecting a neutral flame or a slightly carburizing flame as the heat source, and a two-step spraying process is adopted: The first step is the spraying stage, where alloy powder (containing self-fluxing elements such as B and Si) is fed into the flame stream through a powder feeding device. After the powder is heated to a semi-molten state, it settles... The first step is to deposit a pre-coating layer on the substrate surface preheated to 200~300℃ to form a pre-coating layer with a certain porosity. The second step is the remelting stage. After the pre-coating layer thickness reaches the design value, the flame power is adjusted to uniformly heat the pre-coating layer so that the coating is completely melted. The low-melting-point eutectic formed by B and Si elements reduces the melt viscosity and breaks the oxide film on the substrate surface, promoting micro-area fusion and diffusion between the molten alloy and the substrate surface to form a metallurgical bonding interface. During the remelting process, the flame movement speed and heating temperature must be strictly controlled to avoid overheating of the substrate, which could lead to coarse grains or burn-off of the coating.

[0006] However, martensitic stainless steel undergoes a significant α→γ phase transformation during heating and cooling. Due to the difference in thermal expansion coefficients, nickel-based self-fluxing alloy coatings cannot be formed on martensitic stainless steel, and the problem of coating cracking cannot be solved.

[0007] Therefore, how to develop a novel nickel-based self-fluxing alloy coating is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide a nickel-based self-fluxing alloy powder, its preparation method and application, so as to overcome the shortcomings of the prior art.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A nickel-based self-fluxing alloy powder comprises the following raw materials in mass fractions: Ni 50%~75%, B 1.0%~5%, Si 2.0%~5.0%, Cr 15%~25%, Mo 2.0%~7.0%, W 1.0%~10.0%, Cu 0.1%~10%, Ta 0.5%~5.0%, Nb 0.5%~5.0%, V 0.3%~5.0%, and Co 1.0%~10%.

[0010] Furthermore, the total mass fraction of Ta, Nb, V and Co does not exceed 15.0%.

[0011] Furthermore, the aforementioned nickel-based self-fluxing alloy powder also includes at least one of WC 1.0%~20%, Al2O3 1.0%~20%, and TiO2 1.0%~2.0%.

[0012] A method for preparing a nickel-based self-fluxing alloy powder specifically includes the following steps: (1) Weigh each raw material according to the mass fraction of the above-mentioned nickel-based self-fluxing alloy powder; (2) After mixing the raw materials, smelting, atomizing and crushing, cooling, dehydrating, drying and sieving are carried out to obtain nickel-based self-fluxing alloy powder.

[0013] Furthermore, in step (2) above, the smelting equipment is a medium-frequency smelting furnace with a temperature of 1300~1500℃, preferably 1400℃.

[0014] Furthermore, in step (2) above, the atomizing and crushing equipment is an intermediate drum, the diameter of the guide pipe is 2~5mm, and the water atomization pressure is 8~18MPa.

[0015] Furthermore, the preparation method of the above-mentioned nickel-based self-fluxing alloy powder also includes step (3): mixing the nickel-based self-fluxing alloy powder with at least one of WC, Al2O3 and TiO by ball milling.

[0016] The present invention also claims protection for the use of the above-described nickel-based self-fluxing alloy powder or the nickel-based self-fluxing alloy powder prepared by the above-described preparation method in the processing of martensitic stainless steel coatings.

[0017] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows: This invention adjusts the thermodynamic properties of nickel-based self-fluxing alloy powder to enable it to be formed on martensitic stainless steel substrates and provide protection. It is particularly suitable for surface strengthening treatment of mechanical parts (such as hammers, ball cores, etc.) with strict requirements for coating bonding strength, wear resistance and crack resistance. Attached Figure Description

[0018] Figure 1 The coefficient of thermal expansion of austenitic 304 stainless steel; Figure 2 The coefficient of thermal expansion of 2Cr13 martensitic stainless steel; Figure 3 The coefficient of thermal expansion of nickel-based self-fluxing Ni60 alloy powder; Figure 4 The coefficient of thermal expansion for the alloy composition designed by software simulation is 1; Figure 5 The coefficient of thermal expansion of the alloy composition is 2, calculated by software simulation. Figure 6This refers to the flame spraying process. Figure 7 This refers to the induction cladding process; Figure 8 The image shows the cracking after flame spraying and cooling of conventional Ni60 alloy powder onto the surface of a 2Cr13 martensitic stainless steel hammerhead. Figure 9 The results of PT penetrant testing are obtained after flame spraying conventional Ni60 alloy powder onto the surface of a 2Cr13 martensitic stainless steel sphere core. Figure 10 This is the flame-sprayed morphology of nickel-based self-fluxing alloy powder on the surface of a 2Cr13 martensitic stainless steel sphere core in Example 3 of the present invention. Figure 11 This is the PT penetration test result of flame spraying on the surface of a 2Cr13 martensitic stainless steel sphere core using nickel-based self-fluxing alloy powder in Example 3 of the present invention. Figure 12 The results of Rockwell hardness measurement of nickel-based self-fluxing alloy powder in Example 3 of this invention are shown. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0020] Example 1 Nickel-based self-fluxing alloy powder, comprising the following raw materials in mass fractions: Ni 55%, B 1.5%, Si 5.0%, Cr 18%, Mo 4.5%, W 4.0%, Cu 6.0%, Ta 2.5%, Nb 0.5%, V 1.0%, and Co 2.0%; The preparation method of the above-mentioned nickel-based self-fluxing alloy powder specifically includes the following steps: (1) Weigh each raw material according to the mass fraction of the above-mentioned nickel-based self-fluxing alloy powder; (2) Mix all the raw materials and add them to the medium frequency melting furnace for melting at a temperature of 1300℃. After the melt is completely melted, pour it into the intermediate ladle. The diameter of the guide tube is 2mm and the water atomization pressure is 8MPa. After the melt is broken and cooled to room temperature, it is dehydrated, dried and sieved to obtain nickel-based self-fluxing alloy powder (nickel-based self-fluxing alloy coating is prepared by flame spraying process).

[0021] Example 2 Nickel-based self-fluxing alloy powder, comprising the following raw materials in mass fractions: Ni 65%, B 3.0%, Si 1.0%, Cr 20%, Mo 3.5%, W 2.0%, Cu 1.2%, Ta 1.5%, Nb 0.8%, V 0.4%, and Co 1.6%; The preparation method of the above-mentioned nickel-based self-fluxing alloy powder specifically includes the following steps: (1) Weigh each raw material according to the mass fraction of the above-mentioned nickel-based self-fluxing alloy powder; (2) Mix all the raw materials and add them to the medium frequency melting furnace for melting at a temperature of 1400℃. After the melt is completely melted, pour it into the intermediate ladle. The diameter of the guide tube is 3mm and the water atomization pressure is 12MPa. After the melt is broken and cooled to room temperature, it is dehydrated, dried and sieved to obtain nickel-based self-fluxing alloy powder (nickel-based self-fluxing alloy coating is prepared by induction cladding process).

[0022] Example 3 Nickel-based self-fluxing alloy powder, comprising the following raw materials in mass fractions: Ni 65%, B 2.0%, Si 2.0%, Cr 15%, Mo 2.0%, W 0.6%, Cu 0.7%, Ta 1.5%, Nb 0.3%, V 0.5%, Co 0.4%, and Al2O3 10%; The preparation method of the above-mentioned nickel-based self-fluxing alloy powder specifically includes the following steps: (1) Weigh each raw material according to the mass fraction of the above-mentioned nickel-based self-fluxing alloy powder; (2) Mix the raw materials and add them to the medium frequency melting furnace for melting at a temperature of 1500℃. After the melt is completely melted, pour it into the intermediate ladle. The diameter of the guide tube is 5mm and the water atomization pressure is 18MPa. After the melt is broken and cooled to room temperature, it is dehydrated, dried and sieved to obtain nickel-based self-fluxing alloy powder. (3) Al2O3 powder was uniformly mixed in by ball milling (a nickel-based self-fluxing alloy coating was prepared by flame spraying).

[0023] Performance testing The core idea of ​​this invention is to use nickel-based self-fluxing alloys as the basic system, based on the theory of the additive nature of thermal expansion coefficients and the principle of alloying, and to achieve precise matching between the thermal expansion coefficient of the alloy powder and the target matrix (such as martensitic stainless steel) by screening elements that control the thermal expansion coefficient and optimizing the content ratio of each element. At the same time, it takes into account self-fluxing properties, wear resistance and interfacial metallurgical bonding performance, forming a composition design system with multi-performance synergistic optimization.

[0024] The specific steps are as follows: 1. Determine the target range of thermal expansion coefficient. First, the coefficient of thermal expansion (CTE) of the target substrate (such as austenitic 304 stainless steel and 2Cr13 martensitic stainless steel) was measured in the range from room temperature to the peak cladding cooling temperature. The target CTE range for the nickel-based self-fluxing alloy coating was set to 0.9 to 1.1 times that of the substrate. This range ensures that the difference in thermal shrinkage between the coating and the substrate during cladding cooling is within an acceptable range, effectively reducing thermal stress accumulation. The measurement results are as follows: Figures 1-3 As shown.

[0025] Depend on Figures 1-3 It is known that the coefficient of thermal expansion of nickel-based self-fluxing Ni60 alloy powder (Note: In the nickel-based self-fluxing alloy system, 60 refers not to the nickel content, but to the Rockwell hardness of the material) is closer to that of austenitic 304 stainless steel, but much different from that of 2Cr13 martensitic stainless steel. Therefore, the coefficient of thermal expansion is the underlying cause of coating cracking.

[0026] 2. Constructing a nickel-based self-fluxing basic composition system A core system with self-fluxing properties and basic wear resistance is constructed based on Ni as the base phase (mass fraction 50%~75%). Adding B (1.0%~5%) and Si (2.0%~5.0%) as self-fluxing elements lowers the alloy melting point, ensures the fluidity and self-fluxing properties of the coating during the cladding process, and forms reinforcing phases such as Ni3B and Ni2Si. Adding Cr (15%~25%) improves the corrosion resistance and oxidation resistance of the coating, forming a Cr2O3 passivation film; Adding Mo (2.0%~7.0%), W (1.0%~10.0%), and Cu (0.1%~10%) as wear-resistant reinforcing elements forms a hard carbide phase, improving the coating's hardness and wear resistance.

[0027] 3. Screening elements that regulate the coefficient of thermal expansion and optimizing their content. Based on the theory of thermal expansion coefficient adjustment, two types of control elements are selected and synergistically proportioned to precisely fine-tune the thermal expansion coefficient of the alloy powder to the target range: Low thermal expansion coefficient elements: Select Ta (0.5%~5.0%), Nb (0.5%~5.0%), V (0.3%~5.0%), and Co (1.0~10%). These elements have large atomic radii and high lattice binding energy, which can reduce the thermal expansion coefficient of nickel-based alloys and form MC-type carbides, thus taking into account wear resistance.

[0028] The content of each element must meet the following requirements: the total mass fraction of elements with low expansion coefficients should not exceed 15.0% to avoid excessive addition that could lead to an increase in the alloy's melting point, a decrease in self-fluxing properties, or an increase in brittleness.

[0029] 4. The addition of metallic compounds helps to reduce the coefficient of thermal expansion of the coating. Addable metal compounds include WC, Al2O3, and TiO2. The addition of oxides reduces the coefficient of thermal expansion.

[0030] 5. Iterative optimization of ingredients and performance verification Thermodynamic simulation software (such as Thermo-Calc and JMatPro) was used to calculate the coefficient of thermal expansion, melting point, and phase composition of alloys with different component ratios. Initial screening was conducted to identify composition schemes that met the target range of thermal expansion and basic performance requirements. Subsequently, corresponding alloy powders were prepared, and flame spraying or induction cladding tests were performed to measure the coating's hardness, interfacial bonding strength, and cracking. Based on the test results, the content of each element was iteratively adjusted to ultimately determine the optimal composition scheme. The results are as follows: Figures 4-12 As shown.

[0031] Depend on Figures 4-12 It is known that conventional Ni60 alloy powder (basic formula: carbon C: 0.7~1.1%; chromium Cr: 15~17%; silicon Si: 3.5~5%; boron B: 3~4%; iron Fe: ≤15%; nickel Ni: balance) has a poor match with the thermal expansion coefficient of 2Cr13 martensitic stainless steel, resulting in obvious macroscopic cracks on the coating surface. However, after simulation calculation and adjustment of the conventional component ratio, the nickel-based self-fluxing alloy powder materials of Examples 1-3 of this invention can be normally applied to the surface of martensitic stainless steel without any cracks.

[0032] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A nickel-based self-fluxing alloy powder, characterized in that, The raw materials include the following mass fractions: Ni 50%~75%, B 1.0%~5%, Si 2.0%~5.0%, Cr 15%~25%, Mo 2.0%~7.0%, W 1.0%~10.0%, Cu 0.1%~10%, Ta 0.5%~5.0%, Nb 0.5%~5.0%, V 0.3%~5.0%, and Co 1.0%~10%.

2. The nickel-based self-fluxing alloy powder according to claim 1, characterized in that, The total mass fraction of Ta, Nb, V and Co does not exceed 15.0%.

3. The nickel-based self-fluxing alloy powder according to claim 1 or 2, characterized in that, It also includes at least one of WC 1.0%~20%, Al2O3 1.0%~20%, and TiO2 1.0%~2.0%.

4. A method for preparing a nickel-based self-fluxing alloy powder, characterized in that, Specifically, the following steps are included: (1) Weigh each raw material according to the mass fraction of the nickel-based self-fluxing alloy powder according to any one of claims 1-3; (2) After mixing the raw materials, they are smelted, atomized and crushed, cooled, dehydrated, dried and sieved to obtain the nickel-based self-fluxing alloy powder.

5. The method for preparing a nickel-based self-fluxing alloy powder according to claim 4, characterized in that, In step (2), the smelting equipment is a medium-frequency smelting furnace with a temperature of 1300~1500℃.

6. The method for preparing a nickel-based self-fluxing alloy powder according to claim 4, characterized in that, In step (2), the atomizing and crushing equipment is an intermediate drum, the diameter of the guide pipe is 2~5mm, and the water atomization pressure is 8~18MPa.

7. The method for preparing a nickel-based self-fluxing alloy powder according to claim 4, characterized in that, It also includes step (3): mixing nickel-based self-fluxing alloy powder with at least one of WC, Al2O3 and TiO by ball milling.

8. The application of a nickel-based self-fluxing alloy powder as described in any one of claims 1-3 or a nickel-based self-fluxing alloy powder prepared by the preparation method as described in any one of claims 4-7 in the coating processing of martensitic stainless steel.

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