Powder composition for laser cladding

Abstract

The invention discloses a powder composition for laser cladding. The metal powder is composed of iron-based alloy powder and strengthening material powder, the iron-based alloy powder comprises C, Cr, Si, Mn, B, Mo, Nb, W, V, Ni, Ti, Al, Fe and inevitable impurities, and the strengthening material powder comprises B4C and Nb. According to the cladding coating, niobium carbide, carbide, vanadium carbide and titanium carbide are generated in the cladding process through the iron-based alloy powder to generate a self-enhancement effect, and niobium carbide is further generated in the cladding process through the strengthening material powder to generate an enhancement effect. A laser cladding layer prepared from the powder components has good wear resistance and corrosion resistance, and the hardness and strength of the cladding layer are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the field of alloy materials, and in particular relates to a powder component for laser cladding, a laser cladding coating and a preparation method thereof. Background Art

[0002] Laser cladding technology first appeared in a patent proposed by American scientist Gnanamuth in 1976, and then attracted the attention of many experts in China. This technology involves multiple disciplines such as machinery, materials, metallurgy, and automation. It is a new surface modification technology and material forming technology. This technology is a kind of additive manufacturing technology, which is widely used in the forming of metal parts or local parts structures formed by laser cladding. At the same time, it is also widely used in the remanufacturing of parts and components, and is used to repair some waste parts with high economic value. This technology is different from traditional manufacturing technology and combines material forming and automation technology. It has the ability to control the forming of metal materials at different positions at any time, which is not available in traditional forming manufacturing. Therefore, it shows great advantages. Laser cladding technology is used for the remanufacturing of waste parts, and can remanufacture and repair some large and expensive large parts, thereby achieving huge economic benefits. Laser cladding technology is used for forming manufacturing, and can form some parts that are difficult to manufacture using traditional manufacturing methods or local difficult-to-form structures of formed parts, thereby reducing the difficulty of traditional forming and machining, thereby achieving economic value.

[0003] The alloy powders currently used for forming include nickel-based alloy powder, iron-based alloy powder, and cobalt-based alloy powder. Due to the large-scale application of steel parts in industry, the research on laser cladding forming of iron-based alloy powder has important application and scientific value. Iron-based alloy powder is a self-fluxing powder. The alloy powder contains B and Si elements, so it has deoxidation and slag-making capabilities, many types, good performance, and low cost. Iron-based alloy powder can adapt to the matrix of a variety of different materials, such as carbon steel, stainless steel, cast steel and other materials. In addition, other trace elements can be added to the alloy powder to improve the quality of the cladding layer, improve performance, and reduce defects. Chinese patent application CN202380018543 proposes a tool steel powder for additive manufacturing, which is highly suitable for processing via additive manufacturing and can produce three-dimensional objects with low deformation rate and no cracks. Chinese patent application CN202410647171 proposes a cladding material and test method for laser manufacturing of locomotive axles. This cladding material has high self-melting and austenite stability, realizes solid solution strengthening effect and improves the mechanical properties of the cladding layer, and solves the problems of poor forming quality and substandard mechanical properties of the existing cladding layer. The existing iron-based powder cladding coating has relatively less hard reinforcement inside the cladding layer structure, resulting in generally low hardness of the cladding layer. Simply increasing the carbon content will lead to the precipitation of a large amount of chromium carbide at the grain boundary, which reduces the chromium content in the structure and the corrosion resistance and intergranular corrosion resistance of the cladding layer on the one hand. On the other hand, the accumulation of precipitated phases at the grain boundary also increases the probability of intergranular cracking, further reducing the strength of the cladding layer. With the increasing requirements for cladding quality and the urgent need to reduce raw material costs, it is urgent to develop a powder component for laser cladding and a high-strength and wear-resistant laser cladding coating. Summary of the invention

[0004] In view of this, the present invention proposes a powder component for laser cladding. The cladding coating prepared with the metal powder as raw material has good wear resistance, high strength, excellent welding performance, and good organizational structure in the cladding coating.

[0005] The invention provides a powder component for laser cladding, which consists of iron-based alloy powder and strengthening material powder.

[0006] Further preferably, the iron-based alloy powder is composed of the following chemical components, in terms of mass percentage: C: 3.5%-5.5%, Cr: 18%-21%, Si: 1.4%-1.6%, Mn: 0.5%-1%, B: 0.4%-1%, Mo: 4.5%-6.6%, Nb: 1.2%-1.8%, W: 4.5%-6.5%, V: 1.2%-1.8%, Ni: 4.7%-5.2%, Ti: 1.9%-2.5%, Al: 2.2%-2.8%, and the remainder is Fe and unavoidable impurities; wherein the mass percentage of W and Ti is not less than 7%, and the mass percentage of Nb and V is not less than 2.5%.

[0007] In the above scheme, preferably, the content of the C element is 3.5%-5.5%. C within the eutectic composition range can inhibit the formation of ferrite in the weld deposit, avoid the loss of alloy elements such as Cr, V, and Ti due to the formation of ferrite, and ensure that as much austenite as possible in the weld deposit can be converted into martensite during the cooling process. At the same time, the chromium carbide, vanadium carbide, and titanium carbide in the alloy can refine the grains and effectively improve the strength and hardness of the weld deposit. The C content is matched with the content of V, W, Nb, and Ti elements to ensure that as much C as possible is combined with V, W, Nb, and Ti to avoid intergranular precipitation phases with chromium carbide to reduce the corrosion resistance and strength of the weld deposit. Sufficient carbon content can diffuse and react chemically with elements such as niobium, vanadium, titanium, and tungsten during the welding process to generate micron-sized carbides. Niobium carbide, vanadium carbide, titanium carbide, tungsten carbide, and other carbides have high hardness and high bonding strength with the iron-based matrix, thereby improving wear resistance. If the carbon content is lower than 3.5%, the self-reinforcement effect cannot be fully exerted during the cladding process, resulting in a decrease in wear resistance. Although there are methods in the prior art to improve wear resistance by adding hard material particles such as titanium carbide and tungsten carbide, the wettability of the directly added hard material particles with the iron-based matrix and the uniformity of distribution in the iron-based matrix are poor, and they are easy to fall off. In the present invention, by generating micron-sized carbides during the laser cladding process, it is possible to ensure that the carbides are evenly dispersed in the coating, combined with the matrix grain boundaries, not easy to fall off, and have higher strength.

[0008] In the above scheme, preferably, the content of the Cr element is 18%-21%. Increasing the Cr content can increase the corrosion electrode potential of the cladding layer, prevent the occurrence of corrosion, and improve the corrosion resistance. At the same time, a higher Cr content can reduce the dilution effect of C and avoid the decline of corrosion performance. In addition, Cr can also improve the oxidation resistance of the cladding layer and further improve the corrosion resistance. However, as a ferrite-forming element, too high a Cr content will promote the formation of ferrite in the cladding layer, thereby causing the loss of Cr, V, and Ti alloy elements. In addition, too high a Cr content will also increase the viscosity of the melt, which is not conducive to laser cladding operations. Preferably, the content of the B element is 0.4%-1%, and B forms borides with other elements, thereby improving the hardness and wear resistance of the coating. It can also inhibit the formation of oxides in the cladding layer, and avoid cracks in the cladding layer by reducing oxidation damage. The addition of Cr and B improves the microstructure of the coating, thereby reducing the generation of pores and cracks in the cladding layer during the preparation process.

[0009] In the above scheme, preferably, the content of the Ni element is 4.7%-5.2%. The presence of the Ni element can improve the wettability and ductility of the weld coating on the one hand, and can improve the corrosion resistance of the weld coating on the other hand. Preferably, the content of the Mo element is 4.5%-6.6%, and molybdenum mainly improves the stability of chromium oxide on the surface of the weld coating and improves the corrosion resistance of the weld coating. Preferably, the content of the Si element is 1.4%-1.6%, and Si can improve the fluidity of the melt and facilitate the fluidity of the molten pool during the welding process.

[0010] In the above scheme, preferably, the content of V is 1.2%-1.8%, the content of Nb is 1.2%-1.8%, and the mass percentage of Nb and V is not less than 2.5%. V and Nb are elements that easily form carbides with C. Compared with Cr, V and Nb preferentially combine with C to form vanadium carbide and niobium carbide, which can refine the grains and improve the strength and hardness of the deposited layer on the one hand, and reduce the precipitation of chromium carbide at the grain boundaries on the other hand, thereby improving the corrosion resistance and intergranular strength of the deposited layer. Within the preferred C, V and Nb content range, the eutectic vanadium carbide and niobium carbide can be evenly distributed in the deposited layer structure, improving the overall strength and hardness of the deposited layer.

[0011] In the above scheme, preferably, the content of Ti is 1.9%-2.5%, the content of W is 4.5%-6.5%, and the mass percentage of W and Ti is not less than 7%. Ti and W are also elements that easily form carbides with C. Compared with V, Nb, and Cr elements, Ti and W preferentially combine with C to form titanium carbide and tungsten carbide, reducing or avoiding harmful intergranular precipitation of chromium carbide, thereby improving the strength and corrosion resistance of the weld deposit. However, excessive Ti will combine with Ni to form Ni3Ti, and precipitate along the grain boundaries, resulting in a sharp decrease in the toughness of the weld deposit.

[0012] In the above scheme, preferably, the Al content is 2.2%-2.8%. By adding Ti and Al, TiN and AlN strengthening phases can be formed with nitrogen atoms on the surface of the substrate, thereby further improving the wear resistance of the weld coating. When the Al content is too high, the strength and hardness of the martensite in the weld coating will be reduced, thereby reducing the wear resistance of the weld coating.

[0013] Further preferably, the reinforcing material powder is B4C powder and Nb powder, and the mass ratio of iron-based alloy powder, B4C powder and Nb powder is 4-9:1.5-2:1.5-2. Boron carbide is extremely rich in carbon content and has a high hardness. As an added phase, unmelted boron carbide can improve the wear resistance of the iron-based alloy powder cladding layer. In addition, boron carbide, as a carbon source, can synthesize niobium carbide with Nb during the melting process. Niobium carbide particles are widely used as additives for high-temperature spraying materials, refractory high-temperature materials and cemented carbides due to their high hardness, high melting point and moderate thermal expansion coefficient, and can effectively improve the performance of the composite material layer. The traditional process directly adds niobium carbide powder, which is difficult to directly play a reinforcing effect due to the high melting point of niobium carbide. However, the niobium carbide generated by chemical reaction during the cladding process can not only be evenly distributed in the cladding layer, but also as a reinforcing component, it can further improve the wear resistance and strength of the cladding layer.

[0014] Further preferably, the sphericity of the iron-based alloy powder is greater than 92%, the average particle size is 75 microns to 150 microns, the Hall flow rate is 22 seconds to 28 seconds, and the bulk density is 4.45 g / cm 3 ~6.57g / cm 3 ; The average particle size of the B4C powder and the Nb powder is 100 microns to 150 microns. Good fluidity and appropriate powder particle size can ensure the quality of the weld layer and the stability of the weld. On the one hand, fine powder with too small particle size is prone to agglomeration, and the smaller the powder sphericity, the easier it is for the fine powder to agglomerate. The two work together to cause poor fluidity, and powder blockage is prone to occur during the weld process, affecting the process stability. On the other hand, at a high weld rate, the laser action time is short, the molten pool solidifies quickly, and the energy transferred to the powder per unit time is relatively small. Therefore, powder with too large particle size cannot obtain enough energy to completely melt, and is retained in the weld layer, forming cracks, pores and other unfused defects.

[0015] In a second aspect, the present invention provides a method for preparing a wear-resistant high-strength alloy coating, wherein the alloy coating is prepared from the above-mentioned powder components. In an inert atmosphere, the above-mentioned powder components are used as laser cladding powder, and the surface of the substrate is laser clad, and the cladding coating is obtained by cooling. Considering that the metal powder of the present invention contains a large amount of refractory alloys, when the coating is prepared on the surface of the substrate by laser cladding technology, high energy density input is required for the full melting of the metal particles. Under high energy density input, the molten pool becomes deeper, the stirring effect of the molten pool is enhanced, the refractory metal powder has a large specific gravity, the iron element of the substrate is light, and the substrate element floats, resulting in more substrate elements being mixed. At the same time, high energy density will also cause a deeper heat-affected zone to the substrate, causing the substrate to undergo recrystallization annealing, resulting in changes in the original properties of the substrate material. In order to avoid the above situation, the present invention preferably uses a low energy density laser power for laser cladding, and the laser power of the laser cladding is 600-1kW. Preferably, the spot diameter of the laser cladding is 1.5-3mm. Preferably, the laser scanning speed of the laser cladding is 6-8mm / s. Preferably, the powder feeding speed of the laser cladding is 1 to 1.5 r / min. Preferably, the overlap rate of the laser cladding is 60% to 70%. Preferably, the thickness of the laser cladding coating is 2 to 3 mm. Through low-energy-density laser cladding, the depth of the molten pool and the stirring intensity of the molten pool can be effectively reduced, and the heat-affected zone can be reduced, thereby obtaining a cladding layer with a low iron content.

[0016] The present invention preferably uses a synchronous powder feeding method for laser cladding. The synchronous powder feeding method not only has high powder feeding efficiency, low energy consumption, and good controllability, but is also easy to realize automatically. In order to ensure that efficient and controllable laser cladding can be achieved through the synchronous powder feeding method, the present invention preferably dries the metal powder and loads it into a powder feeder, which is then directly sent to the powder feeding port through a powder feeding tube and sent out together with the laser. During laser cladding, the powder is directly sent into the laser action area, and the powder is melted by the laser and clad on the substrate to form a cladding layer. During the laser cladding process, nitrogen can be used as an inert atmosphere.

[0017] According to a third aspect of the present invention, a laser clad coating is provided, wherein the laser clad coating is prepared by the above-mentioned method for preparing the alloy coating.

[0018] In a fourth aspect, the present invention provides an application of a powder component in preparing a laser-clad coating, wherein the coating is prepared by laser cladding the powder component on the surface of a substrate, and the substrate is preferably 45# steel, ductile iron, 24CrNiMo cast steel or stainless steel.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The laser cladding layer formed by the powder components of the present invention has good wear resistance and corrosion resistance, and also has high strength and toughness and excellent welding performance.

[0021] (2) The iron-based alloy powder in the metal powder of the present invention contains C, Nb, W, V, and Ti elements in appropriate proportions, so that chromium carbide, tungsten carbide, vanadium carbide, and titanium carbide are evenly dispersed in the alloy coating formed by laser cladding, which not only refines the grains and improves the strength and hardness of the coating, but also more effectively inhibits the precipitation of chromium carbide, thereby further improving the corrosion resistance and strength of the alloy coating.

[0022] (3) In the metal powder of the present invention, reinforcing materials boron carbide and niobium powder are added, and during the deposition process, boron carbide uniformly distributed in the deposited layer is directly generated through chemical reaction, thereby improving the wear resistance and strength of the deposited layer, and the unmelted boron carbide further improves the wear resistance of the deposited layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a SEM image of the wear scar of the weld deposited layer prepared in Example 1 of the present invention after friction and wear testing.

[0024] Figure 2 This is a SEM image of the wear scar of the weld deposited layer prepared in Example 2 of the present invention after friction and wear testing.

[0025] Figure 3 This is a SEM image of the wear scar of the weld deposited layer prepared in Example 3 of the present invention after friction and wear testing.

[0026] Figure 4 This is a SEM image of the wear scar of the weld deposited layer prepared in Example 6 of the present invention after friction and wear testing.

[0027] Figure 5 This is a SEM image of the wear scar of the weld-clad layer prepared in Comparative Example 1 of the present invention after friction and wear testing.

[0028] Figure 6 This is a SEM image of the wear scar of the weld deposited layer prepared in Comparative Example 2 of the present invention after friction and wear testing.

[0029] Figure 7 This is a SEM image of the wear scar of the weld deposited layer prepared in Comparative Example 3 of the present invention after friction and wear testing.

[0030] Figure 8 This is a SEM image of the wear scar of the weld deposited layer prepared in Comparative Example 4 of the present invention after friction and wear testing.

[0031] Fig. 9 This is the metallographic structure diagram of the weld deposited layer prepared in Example 1 of the present invention.

[0032] Fig.10 This is the metallographic structure diagram of the weld deposited layer prepared in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0033] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0034] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0035] In the present invention, the chemical composition and content of the metal powder, as well as the preparation method and parameters of the weld-deposited coating, have a great influence on the coating performance. The realization of the coating performance of the present invention requires controlling the chemical composition and content within the scope of the present invention, and preparing according to the preparation method and process parameters of the present invention. The metal powder composition of the present invention is specially designed for iron-based alloys.

[0036] The powder component for laser cladding of the present invention is composed of iron-based alloy powder and strengthening material powder. The iron-based alloy powder of the present invention is composed of the following chemical components in terms of mass percentage:

[0037] C: 3.5%-5.5%;

[0038] Cr: 18%-21%;

[0039] Si: 1.4%-1.6%;

[0040] Mn: 0.5%-1%;

[0041] B: 0.4%-1%;

[0042] Mo: 4.5%-6.6%;

[0043] Nb: 1.2%-1.8%;

[0044] W: 4.5%-6.5%;

[0045] V: 1.2%-1.8%;

[0046] Ni: 4.7%-5.2%;

[0047] Ti: 1.9%-2.5%;

[0048] Al: 2.2%-2.8%;

[0049] The balance is Fe and inevitable impurities.

[0050] Among them, the mass percentage of W and Ti is not less than 7%, and the mass percentage of Nb and V is not less than 2.5%.

[0051] The reinforcing material powders of the present invention are B4C powders and Nb powders, and the mass ratio of the iron-based alloy powders, the B4C powders and the Nb powders is 4-9:1.5-2:1.5-2.

[0052] The iron-based alloy powder of the present invention has a sphericity greater than 92%, an average particle size of 75 microns to 150 microns, a Hall flow rate of 22 seconds to 28 seconds, and a bulk density of 4.45 g / cm 3 ~6.57g / cm 3 ; The average particle size of the B4C powder and the Nb powder is 100 microns to 150 microns.

[0053] The preparation method of the wear-resistant high-strength alloy coating of the present invention adopts the above-mentioned powder components, and comprises the following steps: in an inert atmosphere, using the above-mentioned powder components as laser cladding powder, laser cladding the surface of the substrate, and cooling to obtain a cladding coating; the laser scanning speed of the laser cladding is 6 to 8 mm / s; the laser power of the laser cladding is 600 to 1 kW; the powder feeding speed of the laser cladding is 1 to 1.5 r / min; the spot diameter of the laser cladding is 1.5 to 3 mm; the overlap rate of the laser cladding is 60% to 70%; the thickness of the laser cladding coating is 2 to 3 mm.

[0054] Example 1

[0055] The present embodiment provides a powder composition for laser cladding, which is composed of an iron-based alloy powder and a strengthening material powder. The iron-based alloy powder of the present invention is composed of the following chemical components in terms of mass percentage: C: 3.5%, Cr: 18%, Si: 1.4%, Mn: 0.5%, B: 0.4%, Mo: 4.5%, Nb: 1.2%, W: 4.5%, V: 1.3%, Ni: 4.7%, Ti: 2.5%, Al: 2.2%, and the remainder is Fe and unavoidable impurities. The strengthening material powder of the present invention is B4C powder and Nb powder, and the mass ratio of the iron-based alloy powder, B4C powder, and Nb powder is 4:1.5:1.5; the sphericity of the iron-based alloy powder is 93%, the average particle size is 75 microns, the Hall flow rate is 22 seconds, and the loose density is 6.57g / cm 3 ; The average particle size of the B4C powder and the Nb powder is 100 microns.

[0056] This embodiment provides a method for preparing a wear-resistant high-strength alloy coating, wherein the alloy coating is prepared from the above-mentioned powder components, comprising the following steps:

[0057] In a nitrogen atmosphere, the above-mentioned powder components are used as laser cladding powder to perform laser cladding on the surface of a 45# steel substrate, and a cladding coating with a thickness of 2 mm is obtained by cooling; wherein, the laser scanning speed of the laser cladding is 6 mm / s; the laser power of the laser cladding is 600 W; the powder feeding speed of the laser cladding is 1 r / min; the spot diameter of the laser cladding is 3 mm; and the overlap rate of the laser cladding is 70%.

[0058] Example 2

[0059] The present embodiment provides a powder composition for laser cladding, which is composed of an iron-based alloy powder and a strengthening material powder. The iron-based alloy powder of the present invention is composed of the following chemical components in terms of mass percentage: C: 5.5%, Cr: 21%, Si: 1.6%, Mn: 1%, B: 1%, Mo: 6.6%, Nb: 1.8%, W: 6.5%, V: 1.8%, Ni: 5.2%, Ti: 1.9%, Al: 2.8%, and the remainder is Fe and unavoidable impurities. The strengthening material powder of the present invention is B4C powder and Nb powder, and the mass ratio of the iron-based alloy powder, B4C powder, and Nb powder is 9:2:2; the sphericity of the iron-based alloy powder is 93%, the average particle size is 150 microns, the Hall flow rate is 28 seconds, and the loose density is 4.45g / cm 3 ; The average particle size of the B4C powder and the Nb powder is 150 microns.

[0060] This embodiment provides a method for preparing a wear-resistant high-strength alloy coating, wherein the alloy coating is prepared from the above-mentioned powder components, comprising the following steps:

[0061] In a nitrogen atmosphere, the above-mentioned powder components are used as laser cladding powder to perform laser cladding on the surface of a 45# steel substrate, and a cladding coating with a thickness of 3 mm is obtained after cooling; wherein, the laser scanning speed of the laser cladding is 8 mm / s; the laser power of the laser cladding is 1 kW; the powder feeding speed of the laser cladding is 1.5 r / min; the spot diameter of the laser cladding is 1.5 mm; and the overlap rate of the laser cladding is 60%.

[0062] Example 3

[0063] The present embodiment provides a powder composition for laser cladding, which is composed of an iron-based alloy powder and a strengthening material powder. The iron-based alloy powder of the present invention is composed of the following chemical components in terms of mass percentage: C: 4.5%, Cr: 20%, Si: 1.5%, Mn: 0.8%, B: 0.7%, Mo: 5.5%, Nb: 1.5%, W: 5.5%, V: 1.5%, Ni: 5%, Ti: 2.2%, Al: 2.5%, and the remainder is Fe and unavoidable impurities. The strengthening material powder of the present invention is B4C powder and Nb powder, and the mass ratio of the iron-based alloy powder, B4C powder, and Nb powder is 7:1.5:1.5; the sphericity of the iron-based alloy powder is 93%, the average particle size is 100 microns, the Hall flow rate is 24 seconds, and the loose density is 5.81g / cm 3 ; The average particle size of the B4C powder and Nb powder is 120 microns.

[0064] This embodiment provides a method for preparing a wear-resistant high-strength alloy coating, wherein the alloy coating is prepared from the above-mentioned powder components, comprising the following steps:

[0065] In a nitrogen atmosphere, the above-mentioned powder components are used as laser cladding powder to perform laser cladding on the surface of a 45# steel substrate, and the cladding coating with a thickness of 2 mm is obtained by cooling; wherein, the laser scanning speed of the laser cladding is 7 mm / s; the laser power of the laser cladding is 800 W; the powder feeding speed of the laser cladding is 1.5 r / min; the spot diameter of the laser cladding is 1.5 mm; and the overlap rate of the laser cladding is 70%.

[0066] Example 4

[0067] This embodiment provides a powder composition for laser cladding, which is different from Embodiment 1 in that the mass ratio of the iron-based alloy powder, the B4C powder, and the Nb powder is 9:2:2.

[0068] The preparation method of the wear-resistant high-strength alloy coating is the same as that in Example 1.

[0069] Example 5

[0070] This embodiment provides a powder composition for laser cladding, which is different from Embodiment 2 in that the mass ratio of the iron-based alloy powder, the B4C powder, and the Nb powder is 4:1.5:1.5.

[0071] The preparation method of the wear-resistant high-strength alloy coating is the same as that in Example 2.

[0072] Example 6

[0073] This embodiment provides a powder composition for laser cladding, which is different from Embodiment 3 in that the mass ratio of the iron-based alloy powder, the B4C powder, and the Nb powder is 7:2:2.

[0074] The preparation method of the wear-resistant high-strength alloy coating is the same as that in Example 3.

[0075] Comparative Example 1

[0076] This embodiment provides a powder composition for laser cladding, which is different from Embodiment 1 in that the alloy powder is an iron-based alloy powder, and no strengthening material powder is added to the alloy powder.

[0077] The preparation method of the wear-resistant high-strength alloy coating is the same as that in Example 1.

[0078] Comparative Example 2

[0079] This embodiment provides a powder composition for laser cladding, which is different from Embodiment 1 in that the mass ratio of the iron-based alloy powder, the B4C powder, and the Nb powder is 10:1.5:1.5.

[0080] The preparation method of the wear-resistant high-strength alloy coating is the same as that in Example 1.

[0081] Comparative Example 3

[0082] This embodiment provides a powder composition for laser cladding, which is different from Embodiment 1 in that the mass ratio of the iron-based alloy powder, the B4C powder, and the Nb powder is 3:2:2.

[0083] The preparation method of the wear-resistant high-strength alloy coating is the same as that in Example 1.

[0084] Comparative Example 4

[0085] This embodiment provides a powder composition for laser cladding, which is different from the embodiment 1 in that the iron-based alloy powder of the present invention is composed of the following chemical components by mass percentage: C: 2%, Cr: 18%, Si: 1.4%, Mn: 0.5%, B: 0.4%, Mo: 4.5%, Nb: 1.2%, W: 4.5%, V: 1.3%, Ni: 4.7%, Ti: 2.5%, Al: 2.2%, and the balance is Fe and unavoidable impurities. Among them, the C element content is lower than the C element content in the embodiment 1.

[0086] The preparation method of the wear-resistant high-strength alloy coating is the same as that in Example 1.

[0087] Comparative Example 5

[0088] This embodiment provides a powder composition for laser cladding, which is different from the embodiment 1 in that the iron-based alloy powder of the present invention is composed of the following chemical components by mass percentage: C: 3.5%, Cr: 18%, Si: 1.4%, Mn: 0.5%, B: 0.4%, Mo: 4.5%, Nb: 1.2%, W: 4.5%, V: 1.2%, Ni: 4.7%, Ti: 1.9%, Al: 2.2%, and the balance is Fe and unavoidable impurities. Among them, the mass percentage of W and Ti is less than 7%, and the mass percentage of Nb and V is less than 2.5%.

[0089] The preparation method of the wear-resistant high-strength alloy coating is the same as that in Example 1.

[0090] The laser cladding layers prepared in Examples 1-6 and Comparative Documents 1-5 were tested, wherein the hardness test standard was GB / T230, and the wear test standard was GB T 12444-2006. The test results are shown in Table 1.

[0091] Table 1 Laser cladding layer performance test

[0092]

[0093]

[0094] Friction and wear test results analysis:

[0095] Figure 2 , Figure 4 The wear scar SEM images of the weld-clad layers prepared in Example 2 and Example 6 of the present invention after friction and wear testing are shown in FIG. Figure 2 and 4 It can be seen that the coating surfaces of Examples 2 and 6 are less worn, especially the coating surface of Example 6, which has basically no obvious damage, indicating that the wear-resistant high-strength alloy coating prepared in Example 6 of the present invention has excellent hardness and wear resistance.

[0096] Figure 1 , Figure 3 The wear scar SEM images of the weld-clad layers prepared in Example 1 and Example 3 of the present invention after friction and wear testing are shown in FIG. Figure 1 and 3It can be seen that, although there are more obvious plow-shaped wear marks and particle shedding compared with Example 6, there is no large-area wear and groove-shaped wear marks, indicating that the wear-resistant high-strength alloy coatings prepared in Examples 1 and 3 of the present invention have good hardness and wear performance. At the same time, it can be seen from Example 1 that too low carbon content in the iron-based alloy powder and excessive strengthening material powder will have a negative impact on the improvement of coating hardness and wear resistance. It can be seen from Example 3 that although the iron-based alloy powder contains an appropriate amount of carbon element, the insufficient amount of strengthening material powder added is not conducive to further improving the hardness and wear resistance of the coating.

[0097] Figure 5 This is the SEM image of the wear scar of the cladding layer prepared in Comparative Example 1 of the present invention after the friction and wear test. Figure 5 It can be seen that huge groove-shaped wear marks and particle shedding appeared on the coating surface of Comparative Example 1. Since no reinforcing material powder was added in Comparative Example 1, its hardness and wear resistance were the worst.

[0098] Figure 6 , Figure 7 The wear scar SEM images of the cladding layers prepared in Comparative Example 2 and Comparative Example 3 after friction and wear test are shown in FIG. Figure 6 and 7 It can be seen that the ratio of iron-based alloy powder to reinforcing material powder has a significant effect on the hardness and wear resistance of the weld deposited layer. Although excessive addition of reinforcing material powder or insufficient addition of reinforcing material powder can also play a role in strengthening the coating, the strengthening effect is greatly different from that of Example 6.

[0099] Figure 8 This is the SEM image of the wear scar of the cladding layer prepared in Comparative Example 4 of the present invention after the friction and wear test. Figure 8 It can be seen that the carbon content in the iron-based alloy powder also has a significant effect on the hardness and wear resistance of the weld layer. When the C content is too low, the austenite in the alloy coating is difficult to transform into martensite during the cooling process of the weld layer, and there is not enough carbon to diffuse and react chemically with elements such as niobium, vanadium, titanium, and tungsten during the welding process to generate carbides, niobium carbide, vanadium carbide, titanium carbide, tungsten carbide and other high-hardness carbides. The iron-based alloy powder will not have a self-reinforcement effect during the welding process, thereby reducing the hardness and wear resistance of the weld layer. Although the strengthening material powder will increase the hardness and strength of the coating to a certain extent, the reinforcement effect is not significant at this time.

[0100] Fig. 9 and Fig.10 The metallographic structure diagram of the cladding layer prepared in Example 1 and Comparative Example 4 of the present invention is shown in FIG. Fig. 9 and 10It can be seen that the grains in the weld layer of Example 1 are fine, and the strips of lath martensite are thinner and shorter, while the grains in the weld layer of Comparative Example 4 are larger, and the strips of lath martensite are wider and longer. The iron-based alloy powder in Example 1 contains an appropriate amount of carbon content. During the welding process, it undergoes chemical reactions with elements such as niobium, vanadium, titanium, and tungsten through diffusion to generate carbides, such as niobium carbide, vanadium carbide, titanium carbide, and tungsten carbide with high hardness. These high-hardness carbides play a role in refining the grains and also enhance the hardness and strength of the weld layer. At the same time, sufficient carbon elements promote more transformation of austenite into martensite, resulting in the hardness and wear resistance of the weld layer of Example 1 being significantly better than those of Comparative Example 4.

[0101] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Therefore, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A powder composition for laser cladding, characterized in that: Composed of iron-based alloy powder and strengthening material powder; the iron-based alloy powder, in terms of mass percentage, consists of the following chemical components: C: 3.5%-5.5%, Cr: 18%-21%, Si: 1.4%-1.6%, Mn: 0.5%-1%, B: 0.4%-1%, Mo: 4.5%-6.6%, Nb: 1.2%-1.8%, W: 4.5%-6.5%, V: 1.2%-1.8%, Ni: 4.7%-5.2%, Ti: 1.9%-2.5%, Al: 2.2%-2.8%, and the balance is Fe and unavoidable impurities; Among them, the mass percentage of W and Ti is not less than 7%, and the mass percentage of Nb and V is not less than 2.5%; The strengthening material powder is B4C powder and Nb powder, and the mass ratio of the iron-based alloy powder, B4C powder and Nb powder is 4-9:1.5-2:1.5-2; The iron-based alloy powder has a sphericity greater than 92%, an average particle size of 75 microns to 150 microns, a Hall flow rate of 22 seconds to 28 seconds, and a bulk density of 4.45 g / cm 3 ~6.57g / cm 3 ; The average particle size of the B4C powder and the Nb powder is 100 microns to 150 microns.

2. A method for preparing a wear-resistant high-strength alloy coating, characterized in that: The alloy coating is prepared from the powder component according to claim 1, comprising the following steps: In an inert atmosphere, the powder components are used as laser cladding powder to perform laser cladding on the surface of a substrate, and then cooled to obtain a cladding coating; The laser scanning speed of the laser cladding is 6 to 8 mm / s; the laser power of the laser cladding is 600 to 1 kW; the powder feeding speed of the laser cladding is 1 to 1.5 r / min; the spot diameter of the laser cladding is 1.5 to 3 mm; the overlap rate of the laser cladding is 60% to 70%; the thickness of the laser cladding coating is 2 to 3 mm.

3. A laser cladding coating, characterized in that: The alloy coating is prepared by the preparation method of claim 2.

4. Use of the powder component according to claim 1 in preparing a laser cladding coating, characterized in that: The powder components are melted by laser to prepare a coating on the surface of a substrate, wherein the substrate is 45# steel, ductile iron, 24CrNiMo cast steel or stainless steel.

Images