Refractory high-entropy composite alloy coating with excellent interface combination and preparation method thereof

Abstract

The application discloses a refractory high-entropy composite alloy coating with excellent interface combination and a preparation method thereof. The high-entropy composite coating is prepared by mixing x% of refractory high-entropy alloy powder WMoTaNb and (100-x)% of 316L powder and then performing laser cladding on a 45# steel substrate to be cladded, so that a high-performance refractory high-entropy composite alloy coating with excellent coating-substrate interface combination and a defect-free cladding layer is prepared, and 100%>x%>30%. The application effectively reduces thermal stress, thereby inhibiting the initiation and expansion of cracks, overcomes the problem that the existing WMoTaNb system refractory high-entropy coating is prone to cracking, and realizes the preparation of the high-entropy composite coating with excellent interface combination.

Description

Technical Field

[0001] This invention belongs to the field of metallic materials, specifically relating to a refractory high-entropy composite alloy coating with excellent interfacial bonding prepared by laser cladding technology and its preparation method. Background Technology

[0002] High-entropy alloys (HEAs) differ from traditional engineering alloys. They are a new type of metallic material composed of multiple elements mixed in equal or approximately equal proportions. They possess properties such as high temperature resistance, high strength, resistance to high-temperature oxidation, and excellent wear and corrosion resistance, making them considered high-potential high-temperature materials. Due to their unique alloy phase structure, microstructure, and novel design concepts, they are currently a hot research topic in high-temperature alloy materials. At present, high-temperature materials are mainly nickel-based superalloys, which are widely used as materials for high-temperature components due to their excellent creep resistance, high-temperature resistance, and corrosion resistance. However, the effective operating temperature of nickel-based superalloys is limited to around 1150℃, and even the addition of refractory alloying elements such as titanium dioxide (W) has limited effect on increasing the service temperature. In 2010, Professor Senkov and his colleagues used the concept of high entropy to prepare a series of refractory high entropy alloys (RHEAs) for the first time. They mixed various high-melting-point elements, such as Hf, Nb, Ta, Mo, and W, in equimolar proportions, which gave the alloys excellent high-temperature strength, corrosion resistance, wear resistance, and high-temperature oxidation resistance, and they have excellent application prospects at ultra-high temperatures.

[0003] Currently, existing methods for preparing refractory high-entropy alloys mainly involve bulk and coating / film forms. However, limitations imposed by casting cavities and molds make it difficult to fabricate large-size, complex-structured bulk components. Furthermore, the high cost of using high-entropy alloys as bulk materials limits their industrial and commercial applications. With the development of surface engineering technology, laser cladding technology offers a feasible solution to this problem. Preparing a refractory high-entropy alloy coating on the surface of component materials endows the substrate material with the properties of a refractory high-entropy alloy and significantly reduces manufacturing costs, facilitating engineering and commercial applications. However, during laser cladding, the large melting point differences among refractory elements such as W, Mo, Ta, and Nb make the cladding coating susceptible to the effects of laser energy distribution, temperature gradient, and solidification rate, resulting in significant residual stress. This can lead to defects or even cracking in the cladding layer, hindering large-scale industrial applications. Summary of the Invention

[0004] This invention addresses the problem of cracking that easily occurs during the preparation of cladding coatings. Based on the characteristics of the substrate material to be clad, 316L alloy powder is preferred. WMoTaNb refractory high-entropy alloy powder is mixed with 316L alloy powder at a certain mass percentage, thereby controlling the element content, composition, microstructure, and thermal stress mitigation of the alloy coating. This not only achieves excellent bonding between the coating and the substrate interface and effectively inhibits the initiation and propagation of cracks, but also improves the surface hardness compared to the substrate, thus meeting the needs of industrial applications of materials.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A laser-clad refractory high-entropy composite alloy coating with excellent interfacial bonding and its preparation method are disclosed. The high-entropy composite coating is prepared by laser cladding technology from a mixture of x% refractory high-entropy alloy powder WMoTaNb and (100-x)% 316L powder, where 100% > x% > 30%. The specific steps include:

[0007] Step 1: Mix the refractory high entropy alloy powder WMoTaNb and 316L alloy powder by mass percentage, and dry them under the protection of inert gas to remove trace moisture from the powder, improve the powder's fluidity, and effectively prevent the increase of oxygen content in the powder.

[0008] Step 2: Coating the powder to be clad onto the surface of the substrate using a coaxial powder feeding method, and performing laser cladding using a laser according to the set laser cladding parameters and scanning method.

[0009] Preferably, the substrate to be clad is 45# steel.

[0010] Preferably, 70% ≥ x% ≥ 30%.

[0011] Preferably, in step 1), the purity (wt.%) of each component in the refractory high entropy alloy powder WMoTaNb and 316L powder is greater than 99.9%, and the particle size is 15-50 μm.

[0012] Preferably, in step 1), the drying temperature is 90-120℃ and the time is 6-8h.

[0013] Preferably, in step 2), the substrate to be clad is cleaned with alcohol and acetone to remove surface stains and impurities.

[0014] Preferably, in step 2), during laser cladding, the laser power is 1000-2000W, the scanning rate is 8-50mm / s, the scanning method is single-layer strip reciprocating scanning, the single-track width is 1-3mm, the single-track height is 0.5-1.5mm, and the single-layer height is 0.5-1.5mm; the powder feeding gas flow rate is 8-10L / min, and the gas pressure is 0.5-0.8Mpa; the protective gas is argon, and the argon flow rate is 8-20L / min.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) Due to the high strength and hardness of refractory high-entropy alloys, cracks are easily generated during the preparation of cladding coatings. 316L alloy powder is preferred. After mixing WMoTaNb refractory high-entropy alloy powder with the preferred alloy powder in a certain mass percentage, cladding is performed. This effectively reduces thermal stress, thereby inhibiting the initiation and propagation of cracks. This overcomes the problem of easy cracking of existing WMoTaNb-based refractory high-entropy coatings and realizes the preparation of a high-entropy composite coating with excellent bonding with the substrate interface.

[0017] (2) The present invention regulates the microstructure of the refractory high entropy composite alloy coating by mixing WMoTaNb refractory high entropy alloy powder with preferred transition alloy powder at a certain mass percentage, thereby increasing the microhardness and further improving the impact and wear resistance.

[0018] (3) The operation method of the present invention is simple and flexible. The powder mixing selection and proportion can be made according to the cladding substrate material. It is applicable to the preparation of refractory high-entropy composite alloy coatings of various systems. Attached Figure Description

[0019] Figure 1 The images shown are physical samples of the laser cladding refractory high-entropy composite alloy coatings described in Examples 1-4, where (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4.

[0020] Figure 2 The images shown are SEM images of the bonding region morphology of the laser cladding refractory high-entropy composite alloy coating samples described in Examples 1-4, where (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4.

[0021] Figure 3 The images show the microstructure of the laser-clad refractory high-entropy composite alloy coating samples described in Examples 1-4, where (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. The examples given below are not intended to limit the scope of the invention.

[0023] Example 1

[0024] A laser cladding refractory high-entropy composite alloy coating, wherein the substrate to be clad is 45# steel, preferably 316L stainless steel alloy powder, has a composition of WMoTaNb (50%) / 316L (50%), and the composition percentages are by mass. The process includes the following steps:

[0025] Step 1: Select WMoTaNb refractory high-entropy alloy powder (commercially available from Beijing Yijin New Material Technology Co., Ltd.) and 316L stainless steel powder (commercially available from Beijing Yijin New Material Technology Co., Ltd.) as the powders to be clad, with a purity (wt.%) greater than 99.9% and a particle size range of 35–45 μm. Mix them separately at a mass percentage of 50%. Dry the powders in an inert gas protected drying oven, purging argon gas as a protective gas during the drying process. The drying temperature is 120℃, and the holding time is 8 hours. After the holding time is completed, continuously purging argon gas into the drying oven for cooling until the temperature reaches 25℃. Remove the powders and dry them in an inert gas protected drying oven.

[0026] Step 2: The substrate to be clad is made of 45# steel and cleaned with ethanol to remove surface impurities.

[0027] Step 3: Place the cladding powder into the coaxial powder feeder of the cladding equipment, set the powder feeding gas flow rate to 8L / min and the gas pressure to 0.5Mpa, and spray it onto the surface of the 45# steel to be clad through the powder feeder. At the same time, use a laserline laser to perform laser cladding on the surface of the material to be clad. The laser cladding parameters are: laser power of 1900W, scanning rate of 10mm / s; protective gas flow rate of 20L / min, both protective gas and powder feeding gas are argon, the scanning method is single-layer strip reciprocating scanning, single-track width of 2.5mm, single-track height of 0.7mm, and single-layer height of 1mm.

[0028] The prepared sample is as follows Figure 1 As shown in (a), the sample surface is free of cracks, indicating good cladding quality. The microstructure of the bonding area between the sample coating and the substrate is shown in Figure 1. Figure 2 As shown in (a), the bonding zone exhibits a dense structure, excellent adhesion, and no overall cracks. The microstructure of the sample coating is as follows. Figure 3 As shown in (a), the phase structure is distributed in a network and there are no cracks in the whole.

[0029] Example 2

[0030] A laser cladding refractory high-entropy composite alloy coating, wherein the substrate to be clad is 45# steel, preferably 316L stainless steel alloy powder, has a composition of WMoTaNb (30%) / 316L (70%), the percentages of which are by mass. The process includes the following steps:

[0031] Step 1: Select WMoTaNb refractory high-entropy alloy powder (commercially available from Beijing Yijin New Material Technology Co., Ltd.) and 316L stainless steel powder (commercially available from Beijing Yijin New Material Technology Co., Ltd.) as the cladding powders. Their purity (wt.%) is greater than 99.9%, and the particle size range is 35–45 μm. Mix them separately at a mass percentage ratio of WMoTaNb (30%) / 316L (70%). Dry the powders in an inert gas protected drying oven, purging argon gas as a protective gas during the drying process. The drying temperature is 120℃, and the holding time is 8 hours. After the holding time, continuously purge argon gas into the drying oven for cooling until the temperature reaches 25℃, then remove the powders. Dry the powders again in an inert gas protected drying oven.

[0032] Step 2: The substrate to be clad is made of 45# steel and cleaned with ethanol to remove surface impurities.

[0033] Step 3: Place the cladding powder into the coaxial powder feeder of the cladding equipment, set the powder feeding gas flow rate to 8L / min and the gas pressure to 0.5Mpa, and spray it onto the surface of the 45# steel to be clad through the powder feeder. At the same time, use a laserline laser to perform laser cladding on the surface of the material to be clad. The laser cladding parameters are: laser power of 1900W, scanning rate of 10mm / s; protective gas flow rate of 20L / min, both protective gas and powder feeding gas are argon, the scanning method is single-layer strip reciprocating scanning, single-track width of 2.5mm, single-track height of 0.7mm, and single-layer height of 1mm.

[0034] The prepared sample is as follows Figure 1 As shown in (b), the sample surface is free of cracks, indicating good cladding quality. The microstructure of the bonding area between the sample coating and the substrate is shown in Figure [image missing]. Figure 2 As shown in (b), the bonding zone exhibits a dense structure, excellent adhesion, and no overall cracks. The microstructure of the sample coating is as follows: Figure 3 As shown in (b), the phase structure is a dense network distribution with no cracks overall.

[0035] Example 3

[0036] A laser cladding refractory high-entropy composite alloy coating, wherein the substrate to be clad is 45# steel, preferably 316L stainless steel alloy powder, has a composition of WMoTaNb (70%) / 316L (30%), the percentages of which are by mass. The process includes the following steps:

[0037] Step 1: Select WMoTaNb refractory high-entropy alloy powder (commercially available from Beijing Yijin New Material Technology Co., Ltd.) and 316L stainless steel powder (commercially available from Beijing Yijin New Material Technology Co., Ltd.) as the powders to be clad. Their purity (wt.%) is greater than 99.9%, and the particle size range is 35–45 μm. Mix them separately at a mass percentage ratio of WMoTaNb (70%) / 316L (30%). Dry the powders in an inert gas protected drying oven, purging argon gas as a protective gas during the drying process. The drying temperature is 120℃, and the holding time is 8 hours. After the holding time, continuously purge argon gas into the drying oven for cooling until the temperature reaches 25℃, then remove the powders. Dry the powders again in an inert gas protected drying oven.

[0038] Step 2: The substrate to be clad is made of 45# steel and cleaned with ethanol to remove surface impurities.

[0039] Step 3: Place the cladding powder into the coaxial powder feeder of the cladding equipment, set the powder feeding gas flow rate to 8L / min and the gas pressure to 0.5Mpa, and spray it onto the surface of the 45# steel to be clad through the powder feeder. At the same time, use a laserline laser to perform laser cladding on the surface of the material to be clad. The laser cladding parameters are: laser power of 1900W, scanning rate of 10mm / s; protective gas flow rate of 20L / min, both protective gas and powder feeding gas are argon, the scanning method is single-layer strip reciprocating scanning, single-track width of 2.5mm, single-track height of 0.7mm, and single-layer height of 1mm.

[0040] The prepared sample is as follows Figure 1 As shown in (c), the sample surface is free of cracks, indicating good cladding quality. The microstructure of the bonding area between the sample coating and the substrate is shown in [image missing]. Figure 2 As shown in (c), the bonding zone exhibits a dense structure, excellent adhesion, and no overall cracks. The microstructure of the sample coating is as follows. Figure 3 As shown in (c), the phase structure is a coarse dendritic structure with no cracks.

[0041] Example 4

[0042] A laser cladding process for a refractory high-entropy composite alloy coating is described, wherein the substrate is 45# steel and the coating composition is WMoTaNb. The process includes the following steps:

[0043] Step 1: Select WMoTaNb refractory high-entropy alloy powder (commercially available from Beijing Yijin New Material Technology Co., Ltd.) as the powder to be clad, with a purity (wt.%) greater than 99.9% and a particle size range of 35–45 μm. Dry the powder in an inert gas-protected drying oven, using argon gas as a protective gas during the drying process. The drying temperature is 120℃, and the holding time is 8 hours. After the holding time, continuously introduce argon gas into the drying oven for cooling until the temperature reaches 25℃, then remove the powder. Dry the powder again in an inert gas-protected drying oven.

[0044] Step 2: The substrate to be clad is made of 45# steel and cleaned with ethanol to remove surface impurities.

[0045] Step 3: Place the cladding powder into the coaxial powder feeder of the cladding equipment, set the powder feeding gas flow rate to 8L / min and the gas pressure to 0.5Mpa, and spray it onto the surface of the 45# steel to be clad through the powder feeder. At the same time, use a laserline laser to perform laser cladding on the surface of the material to be clad. The laser cladding parameters are: laser power of 1900W, scanning rate of 10mm / s; protective gas flow rate of 20L / min, both protective gas and powder feeding gas are argon, the scanning method is single-layer strip reciprocating scanning, single-track width of 2.5mm, single-track height of 0.7mm, and single-layer height of 1mm.

[0046] The prepared sample is as follows Figure 1 As shown in (d), large cracks appeared on the sample surface, and part of the cladding layer peeled off. The microstructure of the interface between the sample coating and the substrate is shown in Figure 1. Figure 2 As shown in (d), the bonding area is uneven, and large cracks exist between the substrate and the coating. The microstructure of the sample coating is as follows. Figure 3 As shown in (d), the phase structure is dendritic, and there are unmelted alloy powders and large cracks.

[0047] In summary, this invention, by controlling the mixing mass percentage of WMoTaNb refractory high-entropy alloy powder and 316L alloy powder and employing laser cladding technology, prepares a high-performance refractory high-entropy composite alloy coating with excellent bonding at the coating-substrate interface and a defect-free cladding layer.

Claims

1. A method for preparing a refractory high-entropy composite alloy coating with excellent interfacial bonding, characterized in that, By mass percentage, the refractory high-entropy composite alloy coating is prepared by laser cladding technology after mixing x% of refractory high-entropy alloy powder WMoTaNb and (100-x)% of 316L alloy powder, with 70% ≥ x% ≥ 30%, specifically including the following steps: Step 1: Mix the refractory high entropy alloy powder WMoTaNb and 316L alloy powder by mass percentage, and dry them under the protection of inert gas to remove trace moisture from the powder, improve the powder's fluidity, and effectively prevent the increase of oxygen content in the powder. Step 2: Coat the powder to be clad onto the surface of the substrate using a coaxial powder feeding method, and perform laser cladding using a laser according to the set laser cladding parameters and scanning method; The substrate to be clad is 45# steel.

2. The method as described in claim 1, characterized in that, In step 1), the purity of each component in the refractory high entropy alloy powder WMoTaNb and 316L powder is greater than 99.9%, and the particle size is 15~50μm.

3. The method as described in claim 1, characterized in that, In step 1), the drying temperature is 90-120℃ and the time is 6-8h.

4. The method as described in claim 1, characterized in that, In step 2), the substrate to be clad is cleaned with alcohol and acetone to remove surface stains and impurities.

5. The method as described in claim 1, characterized in that, In step 2), during laser cladding, the laser power is 1000-2000W, the scanning rate is 8-50mm / s, the scanning method is single-layer strip reciprocating scanning, the single-track width is 1-3mm, the single-track height is 0.5-1.5mm, and the single-layer height is 0.5-1.5mm; the powder feeding gas flow rate is 8-10L / min, and the gas pressure is 0.5-0.8Mpa; the protective gas is argon, and the argon flow rate is 8-20L / min.

6. The refractory high-entropy composite alloy coating prepared by the method according to any one of claims 1-5.

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