Special metal material and surface and interface heat treatment process thereof

Abstract

The present application belongs to the technical field of special metal material heat treatment, and particularly relates to a special metal material and a surface and interface heat treatment process thereof. The material composition is as follows in terms of weight: C 0.03-0.08%, Cr 18.0-22.0%, Ni 8.0-12.0%, Nb 0.05-0.15%, Mo 1.5-2.5%, and the balance of Fe. The process comprises: 1050-1150 DEG C solid solution, 850-900 DEG C low-temperature rare earth carburizing, adding 0.3-0.8% nano La2O3, and inductive quenching in a temperature environment of 900-950 DEG C, and finally tempering in a temperature environment of 200-250 DEG C. The present application realizes comprehensive improvement of surface hardness, core impact toughness, neutral salt spray corrosion resistance and other performances. The workpiece made of the special metal material of the present application is suitable for heavy load corrosion working conditions, and the process can be reformed by using existing equipment, thus being low in cost.

Description

Technical Field

[0001] This invention belongs to the field of heat treatment technology for special metal materials, specifically relating to a special metal material and its surface and interface heat treatment process. Background Technology

[0002] Stainless steel is widely used in machinery manufacturing, chemical equipment, and rail transportation due to its excellent corrosion resistance. However, conventional stainless steel has a relatively low surface hardness, making it prone to wear failure under heavy loads and high-frequency friction conditions, which makes it difficult to meet the surface hardness requirements of transmission components.

[0003] To improve the surface hardness of stainless steel, existing technologies mainly employ two types of strengthening schemes. The first is the traditional surface carburizing process, which typically uses high-temperature carburizing at 950-1050℃. While this increases the surface carbon content, chromium (Cr) in stainless steel easily combines with carbon to form continuous network-like and bulk carbides. These carbides damage the passivation film on the stainless steel surface, leading to a significant decrease in corrosion resistance. Furthermore, carburizing results in substantial workpiece deformation, failing to balance hardness and corrosion resistance. The second method is integral quenching and tempering. This method involves heating the entire material to the austenitic region followed by quenching, which improves the overall hardness of the material. However, this leads to a significant decrease in core toughness, and the small difference in hardness between the core and surface fails to meet the requirements for surface wear resistance and core impact resistance. Simultaneously, traditional quenching easily forms coarse martensite characteristics, further exacerbating toughness degradation.

[0004] Therefore, there is an urgent need to develop a special stainless steel material and a matching heat treatment process that simultaneously optimizes surface hardness, core toughness, and overall corrosion resistance. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the purpose of this invention is to provide a special metal material and its surface and interface heat treatment process.

[0006] The technical solution of this invention is: a special metallic material, comprising the following weight components:

[0007] C: 0.03-0.08%, Cr: 18.0-22.0%, Ni: 8.0-12.0%, Nb: 0.05-0.15%, Mo: 1.5-2.5%, Si: ≤0.8%, Mn: ≤1.0%, P: ≤0.03%, S: ≤0.01%, balance Fe.

[0008] Preferably, the mass percentage of Nb is 0.08-0.12%.

[0009] Preferably, the mass percentage of Cr is 19.0-21.0%, and the mass percentage of Mo is 1.8-2.2%.

[0010] To further improve the above technical solution, the present invention also provides a surface and interface heat treatment process for special metal materials, comprising the following steps:

[0011] S1, Solution treatment of substrate: Place the special metal material workpiece in a furnace and keep it at 1050-1150℃ for 1.5-3 hours, then cool it to room temperature with water;

[0012] S2, Low-temperature rare earth carburizing: The workpiece after solid solution treatment is placed in a carburizing furnace and kept at 850-900℃ for 3-5 hours. The carburizing agent is acetone and nitrogen, and 0.3-0.8% of nano lanthanum oxide is added to the carburizing agent. After the heat preservation is completed, it is slowly cooled to 500℃ and then air-cooled to room temperature.

[0013] S3, Local induction hardening and low-temperature tempering: The carburized workpiece is induction heated to 900-950℃ and held for 8-15 minutes, then oil cooled to room temperature; the workpiece is then placed in a furnace and tempered at 200-250℃ for 1-2 hours, and finally air cooled to room temperature.

[0014] Preferably, in step S2, the flow rate ratio of acetone to nitrogen is 1:(35-45).

[0015] Preferably, in step S1, the heat treatment holding time is calculated based on the workpiece thickness, specifically 1h / 20mm.

[0016] Preferably, in step S3, the heating frequency of induction hardening is 15-25 kHz.

[0017] Preferably, the carbon potential of the low-temperature rare earth carburizing in step S2 is controlled at 0.8-1.2% C to regulate the surface carbon content and carbide precipitation density.

[0018] Preferably, in step S2, the cooling rate for slow cooling to 500°C is 5-10°C / min to avoid stress concentration and abnormal carbide precipitation caused by rapid cooling.

[0019] Preferably, in step S2, the depth of the hardened layer in the local induction hardening is 0.5-2.0 mm, and the hardness gradient between the hardened layer and the core is ≤5HRC / mm, in order to ensure a smooth transition of mechanical properties.

[0020] The core of this invention lies in the three-in-one mechanism of precise component control, synergistic process optimization, and quantitative microstructure control. By overcoming the inherent defects of existing technologies, such as carbide coarsening, martensite coarsening, and imbalance between corrosion resistance and hardness, it achieves a synergistic improvement in microstructure and performance. The specific mechanism is as follows:

[0021] Regarding composition control: This invention creatively introduces 0.05-0.15% Nb element, utilizing the fact that the binding energy of Nb to carbon is significantly higher than that of Cr to carbon, preferentially forming nanoscale NbC particles during solid solution treatment, occupying carbon binding sites, and inhibiting Nb binding at its source. Nucleation and growth. Simultaneously, the Cr to Mo ratio is controlled, with 18.0-22.0% Cr ensuring passivation film formation, and 1.5-2.5% Mo enhancing the passivation film's resistance to... The impermeability of Nb, Cr, and Mo is enhanced by their synergistic effect on corrosion resistance, without affecting the preferential precipitation of NbC. Therefore, Nb, Cr, and Mo work together to inhibit carbide degradation. The composition combination of this application breaks through the traditional understanding or inherent concept that high Cr necessarily leads to carbide coarsening, thereby achieving the goal of finely dispersed carbide structure and laying the foundation for the synergy of corrosion resistance and hardness.

[0022] Regarding process synergy: This invention abandons the traditional high-temperature carburizing of 950-1050℃ and chooses low-temperature carburizing of 850-900℃. First, the low-temperature environment reduces the diffusion rate of carbon atoms, avoiding excessive aggregation of carbides; second, the addition of 0.3-0.8% of... Rare earth additives, with atomic radii significantly different from Fe, can adsorb at carbide grain boundaries, inhibiting carbide grain growth. Furthermore, rare earths can purify grain boundaries and improve core toughness. Simultaneously, this invention employs a short holding time of 8-15 minutes to ensure austenite grain refinement, transforming it into fine lath martensite after quenching, thus improving surface hardness. This is followed by low-temperature tempering at 200-250℃ to inhibit excessive martensite decomposition, reduce residual austenite, and prevent hardness fluctuations and dimensional deformation.

[0023] Furthermore, as shown in Figure 13, this temperature range is located at the lower limit of the austenite single-phase region. This ensures uniform diffusion of carbon atoms within the austenite and, because the temperature is lower than that of traditional carburizing, avoids the rapid growth range of austenite grains (1000-1100℃), reducing the risk of excessive carbide aggregation. Therefore, 850-900℃ is safe and effective. Meanwhile, referring to the surface quenching temperature range marked in Figure 12, the induction quenching temperature of 900-950℃ is located in the lower part of the austenite region. The short holding time of 8-15 minutes can ensure the refinement of austenite grains and avoid entering the austenite and cementite dual-phase region shown in Figure 13, which would lead to uneven quenching structure. Furthermore, the design of a solution treatment temperature of 1050-1150℃ for the substrate, based on the single-phase austenitic region range of low-carbon steel in Figure 13 (i.e., when the carbon content is 0.03-0.08%), results in an austenite stability temperature of 912-1200℃. This temperature can completely dissolve the small amount of carbides in the substrate, obtaining a uniform austenitic structure, and is far below the liquidus line, avoiding substrate melting or grain boundary oxidation. Therefore, the process of this invention ensures carburizing effect within the austenitic region while avoiding the grain coarsening range, thus improving the microstructure refinement effect.

[0024] The present invention has the following beneficial effects:

[0025] This invention preferentially forms nano-sized NbC by adding 0.05-0.15% Nb, which occupies carbon bonding sites. Low-temperature carburizing at 850-900℃ reduces the carbon atom diffusion rate, and adding 0.3-0.8% nano-lanthanum oxide adsorbs carbide grain boundaries and inhibits grain growth, thus stabilizing the carbide level into a fine dispersion. This avoids damage to the passivation film and also acts as a second-phase strengthening phase to improve hardness. Induction quenching at 900-950℃ with a short holding time of 8-15 minutes ensures that the austenite grains are refined to a diameter ≤10μm. After quenching, fine lath martensite is formed. Combined with low-temperature tempering at 200-250℃, excessive martensite decomposition is further inhibited, enabling the special metal material to balance hardness and toughness, and significantly improving dimensional stability.

[0026] This invention overcomes the limitation of existing technologies where single-performance optimization requires sacrificing other performances, breaking through the bottleneck of imbalance between hardness, toughness, and corrosion resistance, and achieving synergistic improvement of key performances; specifically, it is manifested in:

[0027] Significantly improved surface hardness and wear resistance: The combined strengthening effect of finely dispersed carbides and fine martensite increases the surface hardness of the material, which is significantly improved compared to existing carburized stainless steel, and can meet the long-term wear resistance requirements of heavy-duty transmission components.

[0028] Significantly improved core toughness and impact resistance: Due to the grain refinement effect of low C and Nb in the composition, combined with slow cooling at 500℃ in the process, the core impact toughness is greatly improved compared with the existing integral quenched stainless steel, effectively resisting the impact load under heavy load conditions.

[0029] Overall corrosion resistance achieves a significant leap: 18.0-22.0% Cr ensures the formation of a passivation film base, 1.5-2.5% Mo enhances the passivation film's resistance to Cl⁻ penetration, and the added advantage of finely dispersed carbides not damaging the passivation film improves the material's neutral salt spray corrosion resistance, which is a significant improvement over existing carburized stainless steel, making it suitable for corrosive environments such as chemical and marine environments.

[0030] In this invention, solution treatment can be performed in a box furnace, low-temperature rare earth carburizing can be performed in a conventional carburizing furnace, and local induction hardening can be performed in an existing induction hardening machine. All of these use mature equipment in the industry, without the need for new special equipment. Enterprises can directly modify their existing production lines, which can significantly reduce equipment investment costs. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the process flow of the present invention;

[0032] Figure 2This is an image showing the effect of carbide formation on carburized gears in the control group.

[0033] Figure 3 This is an image showing the effect of carbide on the carburized gears in experimental group 1 of Example 1;

[0034] Figure 4 This is an image showing the effect of carbide on the carburized gears in experimental group 2 of Example 1;

[0035] Figure 5 This is an image showing the effect of carbide on the carburized gears in experimental group 3 of Example 1;

[0036] Figure 6 This is a diagram showing the effect of martensite in the control group of Example 2;

[0037] Figure 7 These are the effect diagrams of martensite in experimental groups 1 and 3 of Example 2;

[0038] Figure 8 This is a diagram showing the effect of martensite in experimental group 2 of Example 2;

[0039] Figure 9 This is an image showing the effect of residual austenite in the control group of Example 3;

[0040] Figure 10 This is an image showing the effect of residual austenite in experimental group 3 of Example 3;

[0041] Figure 11 The diagram shows the effect of residual austenite in experimental groups 1 and 2 in Example 3;

[0042] Figure 12 for Schematic diagram of alloy phase diagram;

[0043] Figure 13 for Detailed schematic diagram of alloy phase diagram. Detailed Implementation

[0044] The present invention will be further described below through specific embodiments, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements based on the basic idea of ​​the present invention, but as long as they do not depart from the basic idea of ​​the present invention, they are all within the protection scope of the present invention.

[0045] Unless otherwise specified, the reagents used in the following examples and comparative examples are conventional reagents, which can be purchased from conventional reagent manufacturers and distributors. Unless otherwise specified, the methods used are existing technologies.

[0046] The following embodiments illustrate the use of gear workpieces manufactured using the materials described in this application:

[0047] Example 1:

[0048] Objective: To verify the effect of Nb preferentially binding to carbon and inhibiting network carbides by examining the influence of different Nb contents on carbide structure and corrosion resistance.

[0049] Experimental Design:

[0050] Control group: Nb-free, composition (mass%): C 0.05, Cr 20.0, Ni 10.0, Mo 2.0, Si 0.6, Mn 0.8, balance Fe;

[0051] The process in the control group used traditional high-temperature carburizing, which involved a temperature of 980℃ for 4 hours, followed by induction quenching at 950℃ for 20 minutes, and finally tempering at 250℃ for 2 hours.

[0052] Experimental group: Nb content was 0.05%, 0.10%, and 0.15%, respectively; other components were the same as the control group.

[0053] Process employed: First, solution treatment is performed at 1100℃ for 2 hours, followed by low-temperature rare earth carburizing at 880℃ for 4 hours, during which 0.5% rare earth oxides are added. Then, it is induction hardened at 920℃ for 12 minutes, and finally tempered at 220℃ for 1.5 hours.

[0054] The data comparison is as follows:

[0055]

[0056] The combined effect diagrams of the control group and experimental groups 1-3 are as follows: Figures 2 to 5 As can be seen, the control group, which has no Nb, forms large, continuous network carbides during high-temperature carburizing, which damages the passivation film and results in low corrosion resistance.

[0057] After adding Nb to the experimental group, Nb preferentially forms fine NbC with carbon. The carbides have no continuous network, the passivation film is intact, and the corrosion resistance is greatly improved. In addition, Nb refines the grains and improves the core toughness.

[0058] Therefore, by adding 0.05-0.15 Nb, the present invention can effectively control carbides, achieving a balance between high hardness, high toughness, and high corrosion resistance.

[0059] Example 2:

[0060] Objective: To verify the effect of carburizing temperature on martensitic structure and hardness, and to clarify the optimization effect of low-temperature carburizing on martensite refinement and surface wear resistance.

[0061] Experimental Design:

[0062] Control group: Composition (mass%): C 0.05, Cr 20.0, Ni 10.0, Nb 0.10, Mo 2.0, Si 0.6, Mn 0.8, balance Fe; Traditional process: no solution treatment, followed by high-temperature carburizing at 980℃ for 4 hours, then induction quenching at 950℃ for 20 minutes, and finally tempering at 250℃ for 2 hours.

[0063] Experimental group: Carburizing temperatures were 850℃, 880℃, and 900℃, and the composition was the same as the control group; the rest of the process was the same as in Example 1.

[0064] The data comparison is as follows:

[0065]

[0066] The effect diagram combined with the control group is as follows Figure 6 The effect diagrams for experimental groups 1 and 3 are as follows: Figure 7 The effect diagram of experimental group 2 is as follows Figure 8 It can be seen that low-temperature carburizing can obtain fine martensite and the surface hardness is also remarkable. The wear amount of low-temperature carburizing at 880℃ is only 32mg, which is 62.4% lower than the control group. The core hardness drops to 28HRC, with good toughness and small deformation.

[0067] Therefore, low-temperature carburizing at 850-900℃ can refine the martensitic structure, simultaneously improve surface hardness and wear resistance, and reduce deformation. Among these, 880℃ is the optimal carburizing temperature.

[0068] Example 3:

[0069] Objective: To verify the effect of induction hardening holding time on retained austenite and dimensional stability, and to clarify the role of short holding time in controlling retained austenite and reducing dimensional deviations.

[0070] Experimental Design:

[0071] Control group: Traditional long heat preservation was used, induction quenching and heat preservation for 30 min, composition was the same as in Example 2 (Nb 0.10%); process was the same as in Example 2.

[0072] Experimental group: Induction quenching holding time was 8 min, 12 min, and 15 min, respectively, and the composition was the same as the control group; the rest of the process was the same as in Example 2.

[0073] The data comparison is as follows:

[0074]

[0075] Combined with the control group, the effect diagram is as follows Figure 9 The effect diagrams for experimental groups 1 and 2 are as follows: Figure 11 The effect diagram of experimental group 3 is as follows: Figure 10 It can be seen that the control group was kept at a temperature of 30 min, which led to excessive growth of austenite, low surface hardness, decreased hardness after aging, large dimensional deviation, and poor stability.

[0076] The experimental group used a short holding time of 8-15 minutes, which prevented excessive growth of austenite and controlled the residual austenite. When the holding time was 12 minutes, the surface hardness was stable at 58 HRC, and only decreased by 0.8 HRC after aging. The dimensional deviation was 0.08 mm, which was 77.1% lower than the control group. The corrosion resistance reached 500 h.

[0077] Therefore, a short holding time of 8-15 minutes can effectively control the content of residual austenite, improve surface hardness stability and dimensional accuracy, and 12 minutes is the optimal holding time.

[0078] Example 4:

[0079] Objective: To verify the effect of tempering temperature on core toughness and surface hardness, and to clarify the effect of low-temperature tempering on the balance between hardness and toughness.

[0080] Experimental Design:

[0081] Control group: composition same as in Example 2 (Nb 0.10%);

[0082] The control group used a traditional high-temperature carburizing process, namely, a temperature of 980℃ for 4 hours, followed by induction quenching at 950℃ for 20 minutes, and finally tempering at 300℃ for 2 hours.

[0083] Experimental group: tempering temperatures were 200℃, 220℃, and 250℃, and the composition was the same as the control group;

[0084] The process involves first solution treatment at 1100℃ for 2 hours, followed by low-temperature rare earth carburizing at 880℃ for 4 hours, with 0.5% added during this process. Then, induction quenching is performed at 920℃ for 12 minutes, and finally tempering is carried out at a stable temperature for 1.5 hours.

[0085] The data comparison is as follows:

[0086]

[0087] It is evident that the 300℃ high-temperature tempering in the control group resulted in excessive decomposition of martensite, with the surface hardness dropping to 49HRC, the core toughness being only 55J / cm², and the low-temperature toughness being 30J / cm², indicating significant brittleness.

[0088] The experimental group used low-temperature tempering at 200-250℃ to maintain fine martensite. When tempered at 220℃, the surface hardness was 58HRC, the core impact toughness was 85J / cm², and the low-temperature toughness was 60J / cm², which was significantly improved compared with the control group. The elongation at break was 16%, achieving a better balance between hardness and toughness.

[0089] Therefore, tempering at a low temperature of 200-250℃ can significantly improve the toughness of the core while maintaining high surface hardness.

[0090] Example 5:

[0091] Purpose of implementation: To verify rare earth elements The effects of addition amount on carbide distribution and wear resistance were investigated, clarifying the role of rare earth elements in carbide refinement and grain boundary purification.

[0092] Experimental Design:

[0093] Control group: None Add the same ingredients as in Example 2 (Nb 0.10%).

[0094] The process is as follows: first, solution treatment is carried out at 1100℃ for 2 hours, then low-temperature rare earth carburizing is carried out at 880℃ for 4 hours, without low-temperature rare earth carburizing, then induction quenching is carried out at 920℃ for 12 minutes, and finally tempering is carried out at 220℃ in a stable environment for 1.5 hours.

[0095] Experimental group: The addition amounts were 0.3%, 0.5%, and 0.8%, respectively, with the same composition as the control group; the process was the same as the control group (the corresponding amount was added during carburizing). ).

[0096] The data comparison is as follows:

[0097]

[0098] It can be seen that in the control group without rare earth elements, the carbides are coarser, the surface hardness is 54 HRC, the wear amount is 68 mg, and the corrosion resistance is 350 h.

[0099] Experimental group added Subsequently, rare earth elements adsorbed at the carbide grain boundaries, inhibiting their growth. Of these, 0.5%... At that time, the carbides were refined, the surface hardness was 58HRC, the wear amount was 32mg, which was 52.9% lower than the control group, and the corrosion resistance was 500h. The performance improvement of 0.8% addition was not significant, but the cost was increased.

[0100] Therefore, 0.3-0.8% It can effectively refine carbides and improve wear resistance and corrosion resistance; 0.5% is the optimal addition amount.

[0101] Example 6:

[0102] Objective: To verify the effect of Cr content on passivation film and corrosion resistance, and to clarify the mechanism by which Cr and Mo synergistically enhance corrosion resistance.

[0103] Experimental Design:

[0104] Control group: Cr 16.0%, lower than the scope of this invention; composition (mass%): C 0.05, Ni 10.0, Nb 0.10, Mo 2.0, Si 0.6, Mn 0.8, balance Fe;

[0105] Process: High-temperature carburizing at 980℃ for 4 hours, followed by induction quenching at 950℃ for 20 minutes, and finally tempering at 250℃ for 2 hours.

[0106] Experimental group: Cr content was 18.0%, 20.0%, and 22.0%, respectively, with the same composition as the control group (Cr adjusted); process was as in Example 1.

[0107] The data comparison is as follows:

[0108]

[0109] It can be seen that when the control group has 16.0% Cr, the passivation film is incomplete, the carbides are coarsened, the corrosion resistance is only 150h, and the core toughness is 62J / cm².

[0110] In the experimental group, when Cr was 18.0-22.0%, Cr and Mo synergistically enhanced the stability of the passivation film: at 20.0% Cr, the carbide level was 2, the salt spray corrosion resistance was 500h, the corrosion rate was 0.08mm / year, and the core toughness was 85J / cm²; at 22.0% Cr, the corrosion resistance increased slightly, but the toughness decreased slightly.

[0111] Therefore, the synergistic effect of 18.0-22.0% Cr and 1.5-2.5% Mo can significantly improve corrosion resistance, with 20.0% Cr being the optimal content.

[0112] In summary, this application, through precise component ratio and synergistic processing of low-temperature rare earth carburizing, short-hold induction hardening, and low-temperature tempering, can stably achieve improved surface hardness, core toughness, and salt spray corrosion resistance, which is significantly superior to existing technologies. This makes the gears manufactured from the special metal materials of this application suitable for special critical transmission components under heavy-load and corrosive conditions.

[0113] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A surface and interface heat treatment process for a special metal material, characterized in that, The special metal material comprises the following weight components: C: 0.03-0.08%, Cr: 18.0-22.0%, Ni: 8.0-12.0%, Nb: 0.05-0.15%, Mo: 1.5-2.5%, Si: ≤0.8%, Mn: ≤1.0%, P: ≤0.03%, S: ≤0.01%, balance Fe; The process includes the following steps: S1, Solution treatment of substrate: Place the special metal material workpiece in a furnace and keep it at 1050-1150℃ for 1.5-3 hours, then cool it to room temperature with water; S2, Low-temperature rare earth carburizing: The workpiece after solid solution treatment is placed in a carburizing furnace and kept at 850-900℃ for 3-5 hours. The carburizing agent is acetone and nitrogen, and 0.3-0.8% of nano lanthanum oxide is added to the carburizing agent. After the heat preservation is completed, it is slowly cooled to 500℃ and then air-cooled to room temperature. S3, Local induction hardening and low-temperature tempering: The carburized workpiece is induction heated to 900-950℃ and held for 8-15 minutes, then oil cooled to room temperature; the workpiece is then placed in a furnace and tempered at 200-250℃ for 1-2 hours, and finally air cooled to room temperature.

2. The surface and interface heat treatment process according to claim 1, characterized in that, In step S2, the flow rate ratio of acetone to nitrogen is 1:(35-45).

3. The surface and interface heat treatment process according to claim 1, characterized in that, In step S1, the heat treatment holding time is calculated based on the workpiece thickness, specifically 1h / 20mm.

4. The surface and interface heat treatment process according to claim 1, characterized in that, In step S3, the heating frequency of induction hardening is 15-25 kHz.

5. The surface and interface heat treatment process according to claim 1, characterized in that, In step S2, the carbon potential of low-temperature rare earth carburizing is controlled at 0.8-1.2% C to regulate the surface carbon content and carbide precipitation density.

6. The surface and interface heat treatment process according to claim 1, characterized in that, In step S2, the cooling rate for slow cooling to 500℃ is 5-10℃ / min to avoid internal stress concentration and abnormal carbide precipitation caused by rapid cooling.

7. The surface and interface heat treatment process according to claim 1, characterized in that, In step S2, the depth of the hardened layer in the local induction hardening is 0.5-2.0 mm, and the hardness gradient between the hardened layer and the core is ≤5HRC / mm, in order to ensure a smooth transition of mechanical properties.

8. The surface and interface heat treatment process according to claim 1, characterized in that, The mass percentage of Nb is 0.08-0.12%.

9. The surface and interface heat treatment process according to claim 1, characterized in that, The mass percentage of Cr is 19.0-21.0%, and the mass percentage of Mo is 1.8-2.2%.

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