Wear-resistant alloy casting part for electric machinery and production process of wear-resistant alloy casting part

Abstract

The invention discloses a wear-resistant alloy casting part for electric machinery and a production process thereof, and relates to the technical field of electric casting part optimizing.The production process comprises the steps that raw materials are smelted to 1550-1620 DEG C under the protection of argon, and heat preservation is conducted for 30-60 minutes; composite modification treatment; performing low-pressure sand mold casting or die-casting molding; after a casting is austenitized for 1.5-3 hours at the temperature of 980-1050 DEG C, two-stage isothermal quenching is conducted in a salt bath, specifically, in the first stage, heat preservation is conducted for 15-25 minutes at the temperature of 280-320 DEG C, and in the second stage, heat preservation is conducted for 45-60 minutes at the temperature of 180-220 DEG C; and surface laser cladding is conducted, specifically, homogeneous alloy powder is adopted for conducting laser cladding with the lap joint rate being 35-50% on the working face of the casting part. The method has the beneficial effects that through the design principle of multi-scale cooperative strengthening and the cross-dimension coupling effect of material components, the process path and the microstructure, breakthrough improvement of the performance of the wear-resistant alloy casting is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy casting, and more particularly to a wear-resistant alloy casting for electric machinery and its production process. Background Art

[0002] In the field of electric machinery, wear-resistant components under high-speed and heavy-load conditions, such as steam turbine sealing rings and circuit breaker contacts, are constantly facing the dual challenges of surface wear and impact fatigue failure. Although traditional wear-resistant materials such as high-chromium cast iron and martensitic stainless steel have relatively high hardness, due to carbide coarsening, grain boundary brittleness and insufficient toughness, they are prone to spalling or crack propagation under alternating stress. Existing surface strengthening technologies, such as carburizing and plasma spraying, can improve the surface hardness, but there are significant performance mutations between the strengthening layer and the matrix, the interfacial bonding strength is insufficient, and the thickness of the strengthening layer is mostly less than 0.5 mm, making it difficult to meet the deep wear requirements of long-term operation of power equipment. In addition, problems such as element segregation and uneven grain size in conventional casting processes lead to significant material anisotropy, restricting the service reliability of components under complex stresses.

[0003] Currently, the production processes of wear-resistant alloy castings mostly adopt single heat treatment or surface modification methods. For example, adding trace alloying elements to refine carbides or using laser cladding to prepare composite coatings, but there are still significant technical limitations. Although the traditional laser cladding process can improve the surface hardness, obvious weak bonding regions are easily formed between the cladding layer and the matrix, and cracks are prone to propagate due to stress concentration at the interface. In the casting process, conventional sand casting is prone to grain coarsening due to uneven cooling rates, while die casting can improve the density, but the porosity defect rate increases due to turbulent filling. Existing austempering technologies can help obtain bainite structures, but there is insufficient regulation of the coherent interface structure of nano-carbides, and it is difficult to achieve a gradient distribution of the strengthening layer along the thickness direction. In addition, the thickness of the surface strengthening layer is usually relatively thin (<0.5 mm), which cannot meet the deep protection requirements of electric machinery components under long-term wear conditions. It is urgent to break through key technical problems such as the simultaneous improvement of strength and toughness, interfacial gradient transition, and controllable growth of nano-structures through material composition optimization and process collaborative innovation. Summary of the Invention

[0004] To solve the above technical problems, a wear-resistant alloy casting for electric machinery and its production process are provided. This technical solution solves the problems of significant material anisotropy caused by element segregation and uneven grain size in the above-mentioned conventional casting processes, which restricts the service reliability of components under complex stresses.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A production process for a wear-resistant alloy casting for electric machinery, comprising the following steps: Vacuum induction melting: The raw materials are melted to 1550 - 1620 °C under argon protection and held for 30 - 60 minutes; Composite modification treatment: Add rare earth ferrosilicon alloy accounting for 0.15 - 0.35% of the total alloy mass and titanium boron aluminum composite modifier accounting for 0.08 - 0.18% into the melt, simultaneously apply ultrasonic treatment at 20 - 40 kHz for 5 - 8 minutes, and let it stand for 8 - 15 minutes; Low-pressure sand casting: Use a zirconia-based ceramic sand mold formed by 3D printing, control the pouring temperature at 1380 - 1430 °C, the filling pressure at 0.04 - 0.08 MPa, and the holding pressure time at 20 - 40 seconds; Gradient heat treatment: After the casting is austenitized at 980 - 1050 °C for 1.5 - 3 hours, perform two-stage isothermal quenching in a salt bath: the first stage is held at 280 - 320 °C for 15 - 25 minutes, the second stage is held at 180 - 220 °C for 45 - 60 minutes, then perform liquid nitrogen cryogenic treatment with a cooling rate ≥ 50 °C / min, and temper twice at 480 - 550 °C, each time holding for 2 - 4 hours; Surface laser cladding: Use homogeneous alloy powder to perform laser cladding with a lap rate of 35 - 50% on the working surface of the casting, the power density is 200 - 350 W / mm², the scanning speed is 800 - 1200 mm / min, and after cladding, perform plasma nitriding treatment with a nitrided layer depth of 80 - 150 μm and a surface nitrogen content ≥ 8 wt%.

[0006] Preferably, in low-pressure sand casting, the sand mold is provided with a directional solidification channel with a bionic honeycomb structure, an array of chromium steel chillers with a spacing of 12 - 25 mm is embedded in the channel, the surface of the chiller is coated with a 0.1 - 0.3 mm silicon carbide radiation coating, and the ratio of the chiller diameter to the casting wall thickness is 1:3 - 1:5.

[0007] Preferably, the low-pressure sand casting is replaced by a die-casting forming process, and the die-casting forming process includes the following steps: Mold pretreatment: Use a conformal cooling mold made of nanocrystalline H13 steel, preheat the mold to 220 - 280 °C, spray a boron nitride-based mold release agent on the cavity surface, and add 5 - 15 vol% graphene nanosheets to the mold release agent; High-pressure injection: Transfer the melt to the die-casting machine barrel and inject and fill the mold at a pressure of 120 - 250 MPa at a temperature of 630 - 750 °C. Use artificial intelligence to adjust the punch speed curve in real time: the first-stage slow speed is 0.3 - 0.5 m / s, the second-stage medium speed is 1.2 - 1.8 m / s, and the third-stage pressure boost is 2.5 - 3.2 m / s. The speed switching timing is dynamically adjusted based on the feedback of the mold temperature sensor; Controlled cooling: Immediately start the mold circulating water cooling system after the pressure holding ends, cooling the casting to 700 - 750 °C within 8 - 15 seconds, applying a hydrostatic pressure of 0.3 - 0.8 GPa during the cooling process, and then opening the mold to take out the casting.

[0008] Preferably, during high-pressure injection, 0.02 - 0.08% of yttrium oxide nanoparticles by mass of the alloy are added as nucleating agents to the melt before injection, and the treatment is carried out through an electromagnetic-ultrasonic composite field; The specific steps of the electromagnetic-ultrasonic composite field treatment are as follows: While applying electromagnetic stirring at 50 - 80 Hz, superpose ultrasonic oscillation at 20 kHz, and the treatment time is 3 - 6 minutes. Compared with the prior art, the beneficial effects of the present invention are as follows: The beneficial effects of the present invention stem from the design principle of multi-scale collaborative strengthening. Through the cross-dimensional coupling effect of material composition, process path, and microstructure, a breakthrough improvement in the performance of wear-resistant alloy castings is achieved, specifically including: Composition-phase transformation synergistic mechanism: The super-alloying design of chromium and molybdenum elements constructs a coherent system of duplex carbides, where the high-chromium phase forms a rigid framework and the molybdenum-based phase plays a toughening and buffering role. The introduction of trace boron and rare earth elements effectively inhibits the precipitation of coarse carbides by forming stable nanoparticles at grain boundaries, while inducing the fine-grain strengthening effect. This composition design significantly reduces the thermodynamic driving force for the carbide nucleation process, promoting the uniform dispersion of nano-scale strengthening phases.

[0009] Gradient energy field regulation mechanism: The temperature gradient design during the directional solidification stage is combined with gradient heat treatment to establish a dynamic phase transformation control system. Under a specific process path, molybdenum-based carbides preferentially nucleate at high temperatures, forming a sub-micron pre-precipitation phase network; chromium-based carbides then fill the gaps at medium temperatures, forming a three-dimensional interpenetrating strengthening structure. This staged phase transformation process controls the diffusion path of solute atoms, forming a dense nano-carbide layer on the surface and transitioning to a composite strengthening structure with a gradually decreasing gradient towards the matrix.

[0010] Interface energy optimization mechanism: The surface composite treatment technology constructs a low surface energy strengthening phase on the material surface through the synergistic effect of ultra-fast melting and solidification and nitrogen potential infiltration. This special phase structure not only maintains the essential characteristics of ultra-high hardness but also reduces the interface binding energy through the interstitial solid solution of nitrogen atoms, making crack propagation require additional overcoming of multiple energy barriers. The geometric optimization design of the surface micro-texture converts the contact stress concentration into a uniformly distributed microscopic compressive stress field through the stress redistribution effect.

[0011] The multi-scale structure coupling mechanism forms a cross-scale collaborative strengthening network from the interaction of alloying elements at the atomic scale, the spatial distribution of carbides at the mesoscopic scale to the gradient structure design at the macroscopic scale. The surface nano-carbide layer provides the main anti-wear function, the intermediate transition layer relieves the stress mutation through the compositional gradient change, and the matrix fine-grained structure maintains the overall toughness reserve. This structural design breaks through the inverted relationship between hardness and toughness of traditional materials and realizes the performance matching of super-hard surface, transitional buffering and strong and tough matrix. Description of the Drawings

[0012] Figure 1 It is the casting process flow chart of Embodiment 1 to Embodiment 3 of the present invention; Figure 2 It is the casting process flow chart of Embodiment 4 to Embodiment 6 of the present invention. Detailed Embodiments

[0013] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments in the following description are only examples, and those skilled in the art can think of other obvious variations. Embodiment 1:

[0014] A wear-resistant alloy casting for electric machinery, with the mass percentage composition ratio as follows: C 0.3%, Cr 12%, Mo 1.5%, V 0.2%, Nb 0.1%, Si 0.6%, Mn 0.5%, B 0.002%, Re 0.05%, and the balance is Fe; Referring to Figure 1 as shown, the preparation process is as follows: Vacuum induction melting: Melting the raw materials to 1550 °C under argon protection and holding for 60 minutes; Composite modification treatment: Adding 0.15% rare earth ferrosilicon alloy and 0.18% titanium boron aluminum composite modifier based on the total mass of the alloy to the melt, simultaneously applying 20 kHz ultrasonic treatment for 8 minutes, and standing for 15 minutes; Low-pressure sand casting: Using a zirconia-based ceramic sand mold formed by 3D printing, controlling the pouring temperature at 1380 °C, the filling pressure at 0.08 MPa, the holding pressure time at 40 seconds, setting a directional solidification channel with a bionic honeycomb structure in the sand mold, embedding a chromium steel chill array with a spacing of 25 mm in the channel, coating a 0.1 - 0.3 mm silicon carbide radiation coating on the surface of the chill, and the ratio of the diameter of the chill to the wall thickness of the casting is 1:5; Gradient heat treatment: After the casting is austenitized at 980 °C for 3 hours, two-stage isothermal quenching is carried out in a salt bath: the first stage is kept at 280 °C for 25 minutes, the second stage is kept at 180 °C for 60 minutes, followed by liquid nitrogen cryogenic treatment, the cooling rate ≥ 50 °C / min, and tempering is carried out twice at 480 °C, each time keeping warm for 4 hours. The above isothermal quenching stage adopts a magnetic field assisted process, applying a 0.5T steady magnetic field, and the magnetic field direction forms an angle of 60° with the main stress axis of the casting; Surface laser cladding: Homogeneous alloy powder is used for laser cladding with a lap rate of 35% on the working surface of the casting, the power density is 200W / mm², the scanning speed is 800mm / min, and plasma nitriding treatment is carried out after cladding, the nitrided layer depth is 80 - 150μm, and the surface nitrogen content ≥ 8wt%. Example two:

[0015] A wear-resistant alloy casting for electric machinery, with the mass percentage composition ratio as follows: C 1.2%, Cr 25%, Mo 4.5%, V 1.5%, Nb 0.8%, Si 2.0%, Mn 1.8%, B 0.015%, Re 0.3%, and the balance is Fe; Refer to Figure 1 As shown, the preparation process is as follows: Vacuum induction melting: The raw materials are melted to 1620 °C under argon protection and kept warm for 30 minutes; Compound modification treatment: Add rare earth ferrosilicon alloy accounting for 0.35% of the total mass of the alloy and titanium boron aluminum compound modifier accounting for 0.08% to the melt, simultaneously apply 40Hz ultrasonic treatment for 5 minutes, and stand for 8 minutes; Low-pressure sand casting: Use a zirconia-based ceramic sand mold formed by 3D printing, control the pouring temperature at 1430 °C, the filling pressure is 0.04MPa, the pressure holding time is 20 seconds, the sand mold is provided with a directional solidification channel with a bionic honeycomb structure, an array of chromium steel chillers with a spacing of 12mm is embedded in the channel, the surface of the chiller is coated with a 0.1 - 0.3mm silicon carbide radiation coating, and the ratio of the diameter of the chiller to the wall thickness of the casting is 1:3; Gradient heat treatment: After the casting is austenitized at 1050 °C for 1.5 hours, two-stage isothermal quenching is carried out in a salt bath: the first stage is kept at 320 °C for 15 minutes, the second stage is kept at 220 °C for 45 minutes, followed by liquid nitrogen cryogenic treatment, the cooling rate ≥ 50 °C / min, and tempering is carried out twice at 550 °C, each time keeping warm for 2 hours. The above isothermal quenching stage adopts a magnetic field assisted process, applying a 1.2T steady magnetic field, and the magnetic field direction forms an angle of 30° with the main stress axis of the casting; Surface laser cladding: Homogeneous alloy powder is used for laser cladding with a lap rate of 35% on the working surface of the casting. The power density is 350 W / mm², the scanning speed is 1200 mm / min. After cladding, plasma nitriding treatment is carried out. The nitrided layer depth is 80 - 150 μm, and the surface nitrogen content is ≥8 wt%. Example 3:

[0016] A wear-resistant alloy casting for electric machinery, with the mass percentage composition ratio as follows: C 0.8%, Cr 18%, Mo 3.0%, V 1.0%, Nb 0.5%, Si 1.5%, Mn 1.2%, B 0.010%, Re 0.2%, and the balance is Fe; Refer to Figure 1 As shown, the preparation process is as follows: Vacuum induction melting: Under argon protection, the raw materials are melted to 1580 °C and held for 48 minutes; Composite modification treatment: Add rare earth ferrosilicon alloy accounting for 0.28% of the total alloy mass and titanium boron aluminum composite modifier accounting for 0.12% to the melt. Synchronously apply ultrasonic treatment at 35 Hz for 6 minutes and let it stand for 10 minutes; Low-pressure sand casting: Use a zirconia-based ceramic sand mold formed by 3D printing. The pouring temperature is controlled at 1410 °C, the filling pressure is 0.07 MPa, and the pressure holding time is 35 seconds. The sand mold is provided with a directional solidification channel with a bionic honeycomb structure. An array of chromium steel chillers with a spacing of 28 mm is embedded in the channel. The surface of the chiller is coated with a 0.1 - 0.3 mm silicon carbide radiation coating. The ratio of the chiller diameter to the casting wall thickness is 1:4; Gradient heat treatment: After the casting is austenitized at 1020 °C for 2 hours, two-stage isothermal quenching is carried out in a salt bath: the first stage is held at 310 °C for 12 minutes, the second stage is held at 200 °C for 52 minutes. Subsequently, liquid nitrogen cryogenic treatment is carried out, and the cooling rate is ≥50 °C / min. And it is tempered twice at 525 °C, each time holding for 4 hours. The magnetic field-assisted process is adopted in the isothermal quenching stage, and a 1 T steady magnetic field is applied. The magnetic field direction forms a 45° angle with the main stress axis of the casting; Surface laser cladding: Homogeneous alloy powder is used for laser cladding with a lap rate of 35% on the working surface of the casting. The power density is 320 W / mm², the scanning speed is 1100 mm / min. After cladding, plasma nitriding treatment is carried out. The nitrided layer depth is 80 - 150 μm, and the surface nitrogen content is ≥8 wt%; Femtosecond laser is used to process a micro-texture array on the surface of the cladding layer. The texture unit is a hemispherical pit with a diameter of 20 - 50 μm, the areal density is 500 - 1200 pieces / mm², and diamond-like carbon film is deposited in the pit with a film thickness of 1 - 3 μm, and the friction coefficient is ≤0.15. Example 4:

[0017] A wear-resistant alloy casting for electric machinery, with the mass percentage composition ratio as follows: C 0.4%, Cr 18%, Mo 3.5%, V 0.9%, Nb 0.4%, Si 1.2%, Mn 1.0%, B 0.008%, Re 0.15%, and the balance is Fe; Refer to Figure 2 As shown, the preparation process is as follows: Vacuum induction melting: Under argon protection, the raw materials are melted to 1550 °C and held for 60 minutes; Compound modification treatment: Add rare earth ferrosilicon alloy accounting for 0.15% of the total alloy mass and titanium boron aluminum compound modifier accounting for 0.18% to the melt, simultaneously apply ultrasonic treatment at 20 kHz for 8 minutes, and let it stand for 15 minutes; Mold pretreatment: Use a conformal cooling mold made of nanocrystalline H13 steel, preheat the mold to 220 °C, spray a boron nitride-based mold release agent on the cavity surface, and add 5 vol% graphene nanosheets to the mold release agent; High-pressure injection: Add yttrium oxide nanoparticles accounting for 0.02% of the alloy mass as a nucleating agent, and while applying electromagnetic stirring at 50 Hz, superimpose ultrasonic oscillation at 20 kHz. The treatment time is 6 minutes. Transfer the melt to the die-casting machine barrel and inject and fill the mold at a pressure of 250 MPa at a temperature of 630 °C. Use artificial intelligence to adjust the punch speed curve in real time: the first-stage slow speed is 0.3 - 0.5 m / s, the second-stage medium speed is 1.2 - 1.8 m / s, and the third-stage boosting speed is 2.5 - 3.2 m / s. The speed switching timing is dynamically adjusted based on the feedback of the mold temperature sensor; Controlled cooling: Immediately start the mold circulating water cooling system after the pressure holding ends, cool the casting to 700 - 750 °C within 8 - 15 seconds, apply a hydrostatic pressure of 0.3 - 0.8 GPa during the cooling process, and then open the mold to take out the casting; Gradient heat treatment: After austenitizing the casting at 980 °C for 3 hours, perform two-stage isothermal quenching in a salt bath: the first stage is held at 280 °C for 25 minutes, the second stage is held at 180 °C for 60 minutes, then perform liquid nitrogen cryogenic treatment, with a cooling rate ≥ 50 °C / min, and temper twice at 480 °C, each time holding for 4 hours. The isothermal quenching stage uses a magnetic field-assisted process, applying a 0.5 T steady magnetic field, and the magnetic field direction forms a 60° angle with the main stress axis of the casting; Surface laser cladding: Use a homogeneous alloy powder to perform laser cladding with a lap rate of 35% on the working surface of the casting, with a power density of 200 W / mm² and a scanning speed of 800 mm / min. After cladding, perform plasma nitriding treatment, with a nitrided layer depth of 80 - 150 μm and a surface nitrogen content ≥ 8 wt%. Example Five:

[0018] A wear-resistant alloy casting for electric machinery, with the mass percentage composition ratio as follows: C 1.1%, Cr 23%, Mo 4.2%, V 1.4%, Nb 0.7%, Si 1.9%, Mn 1.7%, B 0.013%, Re 0.28%, and the balance being Fe; Refer to Figure 2 As shown, the preparation process is as follows: Vacuum induction melting: Under argon protection, the raw materials are melted to 1620 °C and held for 30 minutes; Composite modification treatment: Add 0.35% of rare earth ferrosilicon alloy and 0.08% of titanium boron aluminum composite modifier based on the total mass of the alloy to the melt, apply 40 Hz ultrasonic treatment for 5 minutes simultaneously, and let it stand for 8 minutes; Mold pretreatment: Use a conformal cooling mold made of nanocrystalline H13 steel, preheat the mold to 280 °C, spray a boron nitride-based mold release agent on the cavity surface, and add 15 vol% graphene nanosheets to the mold release agent; High-pressure injection: Add 0.08% of nano-yttrium oxide based on the mass of the alloy as a nucleating agent, and while applying 80 Hz electromagnetic stirring, superimpose 20 kHz ultrasonic oscillation. The treatment time is 3 minutes. Transfer the melt to the die-casting machine barrel and inject and fill the mold at a pressure of 120 MPa at a temperature of 750 °C. Use artificial intelligence to adjust the punch speed curve in real time: the first stage is slow speed at 0.3 - 0.5 m / s, the second stage is medium speed at 1.2 - 1.8 m / s, and the third stage is pressure boosting at 2.5 - 3.2 m / s. The speed switching timing is dynamically adjusted based on the feedback of the mold temperature sensor; Controlled cooling: Immediately start the mold circulating water cooling system after the pressure holding ends, cool the casting to 700 - 750 °C within 8 - 15 seconds, apply a hydrostatic pressure of 0.3 - 0.8 GPa during the cooling process, and then open the mold to take out the casting; Gradient heat treatment: After austenitizing the casting at 1050 °C for 1.5 hours, perform two-stage isothermal quenching in a salt bath: the first stage is held at 320 °C for 15 minutes, the second stage is held at 220 °C for 45 minutes, and then perform liquid nitrogen cryogenic treatment with a cooling rate ≥ 50 °C / min, and temper twice at 550 °C, each time holding for 2 hours. The isothermal quenching stage adopts a magnetic field-assisted process, applying a 1.2 T steady magnetic field, and the magnetic field direction forms a 30° angle with the main stress axis of the casting; Surface laser cladding: Use a homogeneous alloy powder to perform laser cladding with a lap rate of 35% on the working surface of the casting, with a power density of 350 W / mm² and a scanning speed of 1200 mm / min. After cladding, perform plasma nitriding treatment, with a nitrided layer depth of 80 - 150 μm and a surface nitrogen content ≥ 8 wt%. Example six:

[0019] A wear-resistant alloy casting for electric machinery, with the following mass percentage composition: C 0.7%, Cr 19%, Mo 3.2%, V 1.1%, Nb 0.5%, Si 1.5%, Mn 1.3%, B 0.010%, Re 0.20%, and the balance is Fe; Refer to Figure 2 As shown, the preparation process is as follows: Vacuum induction melting: Under argon protection, the raw materials are melted to 1580 °C and held for 48 minutes; Composite modification treatment: Add rare earth ferrosilicon alloy accounting for 0.28% of the total alloy mass and titanium boron aluminum composite modifier accounting for 0.12% to the melt, simultaneously apply ultrasonic treatment at 35 Hz for 6 minutes, and let it stand for 10 minutes; Mold pretreatment: Use a conformal cooling mold made of nanocrystalline H13 steel, preheat the mold to 260 °C, spray a boron nitride-based mold release agent on the cavity surface, and add 8 vol% graphene nanoplatelets to the mold release agent; High-pressure injection: Add 0.06% of nano-yttrium oxide by mass of the alloy as a nucleating agent, and while applying electromagnetic stirring at 70 Hz, superimpose ultrasonic oscillation at 20 kHz, with a treatment time of 5 minutes. Transfer the melt to the die-casting machine barrel and inject and fill the mold at a pressure of 220 MPa at a temperature of 700 °C. Use artificial intelligence to adjust the punch speed curve in real time: the first stage is slow speed at 0.3 - 0.5 m / s, the second stage is medium speed at 1.2 - 1.8 m / s, and the third stage is boosting speed at 2.5 - 3.2 m / s. The speed switching timing is dynamically adjusted based on the feedback of the mold temperature sensor; Controlled cooling: Immediately start the mold circulating water cooling system after the pressure holding ends, cool the casting to 700 - 750 °C within 8 - 15 seconds, apply a hydrostatic pressure of 0.3 - 0.8 GPa during the cooling process, and then open the mold to take out the casting; Gradient heat treatment: After austenitizing the casting at 1020 °C for 2 hours, perform two-stage isothermal quenching in a salt bath: the first stage is held at 310 °C for 12 minutes, the second stage is held at 200 °C for 52 minutes, and then perform liquid nitrogen cryogenic treatment with a cooling rate ≥ 50 °C / min, and temper twice at 525 °C, each time holding for 4 hours. The magnetic field-assisted process is used during the isothermal quenching stage, applying a 1 T steady magnetic field, and the magnetic field direction forms an angle of 45° with the main stress axis of the casting; Surface laser cladding: Use a homogeneous alloy powder to perform laser cladding with a lap rate of 35% on the working surface of the casting, with a power density of 320 W / mm² and a scanning speed of 1100 mm / min. After cladding, perform plasma nitriding treatment, with a nitrided layer depth of 80 - 150 μm and a surface nitrogen content ≥ 8 wt%; A femtosecond laser is used to process a micro-texture array on the surface of the cladding layer. The texture unit is a hemispherical pit with a diameter of 20 - 50 μm, and the areal density is 500 - 1200 pieces / mm². A diamond-like carbon film is deposited in the pit, with a film thickness of 1 - 3 μm and a friction coefficient ≤ 0.15.

[0020] The wear-resistant alloy castings for electric machinery prepared based on Examples 1 to 6 all have a nano-carbide strengthening layer with a gradient distribution from the outside to the inside. The thickness of the strengthening layer is 0.8 - 2.5 mm, and a transition layer with a width of 50 - 150 μm is provided between the strengthening layer and the matrix. The gradient change rate of the Cr / Mo atomic ratio in the transition layer is 2 - 5% / μm. Specifically, in the nano-carbide strengthening layer, the Cr7C3 phase and the Mo2C phase form a coherent interface structure, the lattice misfit degree of the two phases ≤ 3%, the average grain size is 50 - 180 nm, the volume fraction is 25 - 40%, and it shows a decreasing gradient distribution of 10 - 15% along the thickness direction; Specifically, the formation mechanism of the strengthening layer (nano-carbide layer): Basis of alloy composition design: Cr / Mo synergy: The high content design of Cr and Mo provides sufficient solute atoms for carbide formation; B / Re micro-alloying: Adding B and Re forms ReB2 nanoparticles, which serve as the heterogeneous nucleation substrate for carbides.

[0021] Key control of gradient heat treatment: Cr and Mo are fully dissolved in austenite to form a supersaturated solid solution. The rare earth element Re segregates at the grain boundaries, inhibiting grain coarsening.

[0022] Two-stage isothermal quenching: The first stage: Induce bainite transformation, and Mo preferentially combines with C to form a Mo2C pre-precipitation phase. The second stage: Cr combines with C to form the Cr7C3 phase, which grows coherently with Mo2C.

[0023] Liquid nitrogen cryogenic treatment (-196 °C): Supercooled austenite undergoes martensitic transformation, generating a high density of dislocations. Carbides preferentially precipitate at the dislocation lines, and the diffusion is frozen during the cryogenic process, forming a gradient distribution of carbides.

[0024] Secondary strengthening by surface laser cladding: The laser power density of 200 - 350 W / mm² remelts the surface layer, and after partial dissolution of the carbides, rapid solidification occurs (cooling rate > 10 4 °C / s), and the size of the nano-carbides (Cr7C3 / Mo2C) is refined to 50 - 80 nm.

[0025] Plasma nitriding treatment: The surface nitrogen content ≥ 8 wt%, forming an ε-Fe 2-3 -N phase, which forms an N-Cr-Mo composite strengthening phase with the carbides.

[0026] The formation mechanism of the transition layer: Bionic honeycomb structure sand molds in Embodiments 1 to 3: The chromium steel chill arrays guide the directional heat conduction, and the silicon carbide radiation coating accelerates the surface cooling to form a temperature gradient.

[0027] Solute redistribution during solidification: Due to the difference in partition coefficients, k_Cr = 0.85 and k_Mo = 0.65, Cr and Mo are enriched at the front of the solid-liquid interface, forming a composition transition zone.

[0028] Yttrium oxide nanoparticle nucleating agents in Embodiments 4 to 6: Y2O3 nanoparticles serve as heterogeneous nucleation sites to refine the primary phase.

[0029] Electromagnetic-ultrasonic composite field treatment: Electromagnetic stirring at 50 - 80 Hz, the Lorentz force drives the melt flow and is superimposed with 20 kHz ultrasonic waves. The cavitation effect breaks dendrites, making the Cr / Mo atoms gradient-distributed along the flow field direction.

[0030] Hydrostatic pressure cooling: A pressure of 0.3 - 0.8 GPa inhibits the formation of microvoids and forces the Cr / Mo atoms to diffuse along the pressure gradient.

[0031] Femtosecond laser micro-texture in Embodiments 3 and 6: Laser shock induces dislocation slip, dislocation walls are formed in the transition layer, guiding the orderly arrangement of carbides along the dislocation lines.

[0032] Specifically, the performance parameters of Embodiments 1 to 6 are as follows in the table;

[0033] Based on Embodiments 2 and 4, it can be seen that in this solution, high C + high Cr are more likely to form Cr7C3 carbides, thereby increasing the surface hardness of the casting, but at the same time, excessive carbides cut the matrix, resulting in a decrease in toughness; Based on Embodiments 2, 3, and 6, it can be seen that the femtosecond laser forms a diamond-like carbon film on the surface of the casting, which can effectively reduce the friction coefficient of the casting surface. However, due to the insufficient density of the casting itself in the sand casting process, the bonding strength between the surface carbon film and the casting is not high, and there is no obvious improvement in the surface wear amount of the casting. In Embodiment 6, through die-casting densification in coordination with the diamond-like carbon film, the bonding strength of the diamond-like carbon film is improved, significantly reducing the friction coefficient of the casting body.

[0034] Based on the above embodiments, the advantages of the present invention are as follows: Through composition boundary control (C-Cr-Mo-V-Nb synergy), multi-scale process coupling (magnetic field quenching / die casting densification / femtosecond micro-texturing), and interface gradient design (Cr / Mo atomic ratio gradient change rate of 2-5% / μm), the following are achieved: Synergy of hardness and toughness: hardness ≥ 58 HRC under impact toughness ≥ 25 J / cm², breaking through the dilemma of the inverse relationship between strength and toughness of traditional high-chromium cast iron; Ultra-long wear resistance life: wear amount ≤ 0.20 mg / cm² in 500 h, which is 3-10 times higher than that of the traditional process (≥ 0.65 mg / cm²); Process universality: compatible with sand casting / die casting, suitable for the customized needs of complex wear-resistant parts (sealing rings / blades / contacts) in power machinery.

[0035] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection required by the present invention is defined by the appended claims and their equivalents.

Claims

1. A wear-resistant alloy casting for electric machinery, characterized in that: The wear-resistant alloy comprises the following components by mass percentage: C0.3-1.2%, Cr12-25%, Mo1.5-4.5%, Ni0.8-3.2%, V0.2-1.5%, Nb0.1-0.8%, Si0.6-2.0%, Mn0.5-1.8%, B0.002-0.015%, Re0.05-0.3%, and the balance is Fe; the surface hardness of the casting is ≥58HRC, the impact toughness is ≥25J / cm², and it has a nano-carbide strengthening layer with a gradient distribution from the outside to the inside, the thickness of the strengthening layer is 0.8-2.5mm, and a transition layer with a width of 50-150μm is provided between the strengthening layer and the substrate, and the gradient change rate of the Cr / Mo atomic ratio in the transition layer is 2-5% / μm.

2. The wear-resistant alloy casting for electric power machinery according to claim 1, characterized in that: The Cr7C3 phase and the Mo2C phase in the nanocarbide strengthening layer form a coherent interface structure, the lattice mismatch between the two phases is ≤3%, the average grain size is 50-180nm, the volume fraction is 25-40%, and a decreasing gradient distribution of 10-15% is presented along the thickness direction.

3. A production process for wear-resistant alloy castings for electric machinery, applicable to the wear-resistant alloy castings for electric machinery as claimed in any one of claims 1-2, characterized in that: The following steps are involved: Vacuum induction melting: melt the raw materials to 1550-1620℃ under argon protection and keep warm for 30-60 minutes; Composite modification treatment: add 0.15-0.35% of rare earth ferrosilicon alloy and 0.08-0.18% of titanium boron aluminum composite modifier to the melt, apply 20-40kHz ultrasonic treatment for 5-8 minutes, and let stand for 8-15 minutes; Low-pressure sand casting: Using 3D printed zirconia-based ceramic sand mold, the pouring temperature is controlled at 1380-1430°C, the filling pressure is 0.04-0.08MPa, and the holding time is 20-40 seconds; Gradient heat treatment: After the casting is austenitized at 980-1050℃ for 1.5-3 hours, it is austempered in a salt bath in two stages: the first stage is kept at 280-320℃ for 15-25 minutes, the second stage is kept at 180-220℃ for 45-60 minutes, followed by liquid nitrogen cryogenic treatment, cooling rate ≥50℃ / min, and tempered twice at 480-550℃, each time keeping for 2-4 hours; Surface laser cladding: Use homogeneous alloy powder to perform laser cladding on the working surface of the casting with an overlap rate of 35-50%, a power density of 200-350W / mm², a scanning speed of 800-1200mm / min, and plasma nitriding treatment after cladding. The depth of the nitriding layer is 80-150μm, and the surface nitrogen content is ≥8wt%.

4. The production process for wear-resistant alloy castings for electric machinery according to claim 3 is characterized in that: In low-pressure sand casting, the sand mold is provided with a directional solidification channel of a bionic honeycomb structure, and a chrome steel chill array with a spacing of 12-25 mm is embedded in the channel. The surface of the chill is coated with a 0.1-0.3 mm silicon carbide radiation coating, and the ratio of the chill diameter to the casting wall thickness is 1:3-1:

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5. The production process for wear-resistant alloy castings for electric machinery according to claim 3, characterized in that: The isothermal quenching stage in the gradient heat treatment adopts a magnetic field assisted process, applying a 0.5-1.2T constant magnetic field, and the direction of the magnetic field is at an angle of 30-60° to the principal stress axis of the casting.

6. The production process for wear-resistant alloy castings for electric machinery according to claim 3, characterized in that: The low-pressure sand casting is replaced by a die-casting process, and the die-casting process comprises the following steps: Mold pretreatment: Use conformal cooling mold made of nanocrystalline H13 steel, preheat the mold to 220-280℃, spray boron nitride-based mold release agent on the cavity surface, and add 5-15vol% graphene nanosheets to the mold release agent; High-pressure injection: The melt is transferred to the barrel of the die-casting machine, and the injection is performed at a temperature of 630-750°C and a pressure of 120-250MPa. Artificial intelligence is used to adjust the punch speed curve in real time: the first-level slow speed is 0.3-0.5m / s, the second-level medium speed is 1.2-1.8m / s, and the third-level boost is 2.5-3.2m / s. The speed switching timing is dynamically adjusted based on the feedback from the mold temperature sensor; Controlled cooling: Immediately after the pressure holding is completed, the mold circulating water cooling system is started to cool the casting to 700-750℃ within 8-15 seconds. During the cooling process, 0.3-0.8GPa hydrostatic pressure is applied, and then the mold is opened to take out the casting.

7. The production process for wear-resistant alloy castings for electric machinery according to claim 6, characterized in that: In high-pressure injection, nano-yttrium oxide accounting for 0.02-0.08% of the alloy mass is added to the melt as a nucleating agent before injection, and then treated by electromagnetic-ultrasonic composite field; The specific steps of the electromagnetic-ultrasonic composite field treatment are: applying 50-80 Hz electromagnetic stirring while superimposing 20 kHz ultrasonic oscillation, and the treatment time is 3-6 minutes.

8. The production process for wear-resistant alloy castings for electric machinery according to any one of claims 3 to 6, characterized in that: After the surface laser cladding treatment, a femtosecond laser is used to process a micro-texture array on the surface of the cladding layer. The texture unit is a hemispherical pit with a diameter of 20-50μm and a surface density of 500-1200 / mm². A diamond-like carbon film is deposited in the pit with a film thickness of 1-3μm and a friction coefficient of ≤0.15.

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