Heterogeneous stainless steel layered composite board as well as preparation method and application thereof

Abstract

The invention discloses a heterogeneous stainless steel layered composite board and a preparation method and application thereof, and belongs to the technical field of metal materials. The method comprises the following steps: carrying out alternative additive manufacturing on 316L powder and 420 powder by adopting a laser powder bed melting process; before the 420 martensitic stainless steel layer is prepared, a base plate is preheated; during powder replacement additive manufacturing, firstly, the surface of the previous stainless steel layer is paved with preparation powder of the next stainless steel layer with the thickness not larger than 0.02 mm, and then the laser powder bed melting process is carried out at least two times; the microstructure after heat treatment is composed of an austenite structure and a martensite structure alternately. A stainless steel layer interface in the prepared heterogeneous stainless steel layered composite plate presents good metallurgical bonding, and the heterogeneous stainless steel layered composite plate has the characteristics of high strength, high toughness and low cost, has high plasticity of a 316L austenitic stainless steel material and high strength of a 420 martensitic stainless steel material, and is suitable for key parts of aerospace, automobiles, ships and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of metal materials, and in particular to a heterogeneous stainless steel layered composite plate material and a preparation method and application thereof. Background Art

[0002] According to the organizational state, stainless steel can often be divided into austenitic steel, martensitic steel, ferritic steel, austenitic-ferritic (duplex) stainless steel and precipitation hardening stainless steel.

[0003] Austenitic stainless steel, represented mainly by 316L, has good plasticity, toughness, weldability, corrosion resistance, and is non-magnetic or weakly magnetic. It has good corrosion resistance in both oxidizing and reducing media and is often used to make acid-resistant equipment, such as corrosion-resistant containers and equipment linings, and transportation pipelines. In addition, it can also be used as the main material of stainless steel watch accessories, but the strength of austenitic stainless steel is generally low.

[0004] Martensitic stainless steel, represented mainly by 420, has high strength, high hardness and excellent wear resistance. It is often used to manufacture parts with high mechanical properties requirements, such as springs, turbine blades, hydraulic press valves, etc. However, the plasticity of martensitic stainless steel is generally poor.

[0005] How to produce composite materials that can take advantage of both the high plasticity of austenitic stainless steel and the high strength of martensitic stainless steel has become a current research hotspot.

[0006] At present, the preparation methods of heterogeneous material layered composite plates mainly include hot rolling composite, hot pressing composite, molten metal immersion plating, explosive welding, etc., but there are often problems such as poor interface bonding, unclear element diffusion, and poor performance, which leads to poor performance of heterogeneous material layered composite plates and it is difficult to effectively combine the respective performance advantages of austenitic stainless steel and martensitic stainless steel.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] The object of the present invention is to provide a heterogeneous stainless steel layered composite plate and a preparation method and application thereof, so as to solve or improve the above technical problems.

[0009] The present invention can be implemented like this:

[0010] In a first aspect, the present invention provides a method for preparing a heterogeneous stainless steel layered composite plate, comprising the following steps: alternately additively manufacturing 316L powder and 420 powder using a laser powder bed melting process to obtain a heterogeneous stainless steel layered composite plate consisting of alternating 316L austenitic stainless steel layers and 420 martensitic stainless steel layers;

[0011] Wherein, before preparing the 420 martensitic stainless steel layer, the substrate is preheated;

[0012] In powder-changing additive manufacturing, the powder for preparing the next stainless steel layer with a thickness not exceeding 0.02 mm is first laid on the surface of the previous stainless steel layer, and then the laser powder bed melting process is performed at least twice.

[0013] In an optional embodiment, the process parameters of the laser powder bed melting process include: laser power of 150W to 400W, scanning speed of 500mm / s to 2500mm / s, scanning spacing of 0.06mm to 0.13mm, and powder thickness of 0.03mm to 0.05mm.

[0014] In an alternative embodiment, the 316L powder and the 420 powder are independently prepared by a powder preparation method.

[0015] In an alternative embodiment, the powder preparation method is a vacuum air atomization method.

[0016] In an alternative embodiment, the particle sizes of the 316L powder and the 420 powder are independently 15 μm to 53 μm.

[0017] In an optional embodiment, the method further includes: heat treating the product obtained by additive manufacturing.

[0018] In an optional embodiment, the heat treatment is carried out at 500° C. to 800° C. for 0.5 h to 4 h, followed by furnace cooling or air cooling.

[0019] In an optional embodiment, the heat treatment is carried out at 600° C. for 2 hours, followed by furnace cooling or air cooling.

[0020] In a second aspect, the present invention provides a heterogeneous stainless steel layered composite plate material prepared by the preparation method of any one of the aforementioned embodiments.

[0021] In an optional embodiment, the austenite structure in the 316L austenitic stainless steel layer is in a strip shape.

[0022] In an alternative embodiment, austenite structure is populated with high density of dislocation cells.

[0023] In an alternative embodiment, the high density of dislocation cells includes dislocation tangles and cellular substructures.

[0024] In an optional embodiment, the microstructure of the 316L austenitic stainless steel layer also contains large-angle unit cell boundaries and a large number of twins.

[0025] In an optional embodiment, the microstructure of the 420 martensitic stainless steel layer includes a micrometer-scale cellular structure and submicrometer-scale acicular martensite, and the submicrometer-scale acicular martensite is distributed in the cellular structure.

[0026] In an optional embodiment, in the heterogeneous stainless steel layered composite plate, the Ni element gradually decreases from the 316L stainless steel layer to the 420 stainless steel layer.

[0027] In an optional embodiment, the Ni content of the 420 stainless steel layer at a position 200 μm away from the interface is 2 wt % to 3 wt %.

[0028] In an optional embodiment, the interface between 316L austenitic stainless steel and 420 martensitic stainless steel is well metallurgically bonded.

[0029] In an optional embodiment, the heterogeneous stainless steel layered composite plate has a tensile strength of 1022 MPa to 1203 MPa, a yield strength of 873 MPa to 1052 MPa, and an elongation after fracture of 16.2% to 30.7%.

[0030] In a third aspect, the present invention provides a component, wherein the raw material for preparing the component comprises the heterogeneous stainless steel layered composite plate material of any one of the aforementioned embodiments.

[0031] In alternative embodiments, the component comprises an aerospace, automotive, or marine component.

[0032] The beneficial effects of the present invention include:

[0033] The preparation method of the heterogeneous stainless steel layered composite plate provided by the present invention can achieve good interface metallurgical bonding between the 316L austenitic stainless steel layer and the 420 martensitic stainless steel layer, and there is obvious diffusion behavior of Ni between the layers. The heterogeneous stainless steel layered composite plate prepared by the preparation method provided by the present invention is composed of 316L austenitic stainless steel layers and 420 martensitic stainless steel layers alternately, has the characteristics of high strength, high toughness and low cost, and takes into account the high plasticity of 316L austenitic stainless steel material and the high strength of 420 martensitic stainless steel material, and is suitable for key parts such as aerospace, automobiles, and ships. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 A schematic diagram of the layered structure of the heterogeneous stainless steel layered composite plate provided by the present invention;

[0036] Figure 2The scanning electron microscope image of the morphology of the 316L austenitic stainless steel powder used in the embodiments and comparative examples of the present invention;

[0037] Figure 3 The scanning electron microscope image of the morphology of the 420 martensitic stainless steel powder used in the embodiments and comparative examples of the present invention;

[0038] Figure 4 This is a scanning electron microscope image of the bonding interface of the heterogeneous stainless steel layered composite plate prepared in Example 1 of the present invention;

[0039] Figure 5 This is an EDS energy spectrum surface scanning analysis diagram (Ni element) of the bonding interface of the heterogeneous stainless steel layered composite plate prepared in Example 1 of the present invention;

[0040] Figure 6 This is an EDS energy spectrum line scanning analysis diagram (Ni element) of the bonding interface of the heterogeneous stainless steel layered composite plate prepared in Example 1 of the present invention;

[0041] Figure 7 X-ray diffraction spectra of the 316L stainless steel layer and the 420 stainless steel layer in the heterogeneous stainless steel layered composite plate prepared in Example 1 of the present invention;

[0042] Figure 8 101 represents Example 1, 102 represents Comparative Example 1, and 103 represents Comparative Example 2;

[0043] Fig. 9 This is a scanning electron microscope image of the tensile fracture of the heterogeneous stainless steel layered composite plate prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0045] The heterogeneous stainless steel layered composite plate provided by the present invention and its preparation method and application are described in detail below.

[0046] The present invention provides a method for preparing a heterogeneous stainless steel layered composite plate, comprising the following steps: using a laser powder bed melting process to perform additive manufacturing on 316L powder and 420 powder alternately to obtain a heterogeneous stainless steel layered composite plate (such as a 316L austenitic stainless steel layer and a 420 martensitic stainless steel layer alternately composed of) Figure 1shown).

[0047] In some optional embodiments, the 316L powder and the 420 powder are independently prepared by a powder preparation method, wherein the powder preparation method may be, for example, a vacuum air atomization method.

[0048] Preferably, the particle sizes of the 316L powder and the 420 powder are independently 15 μm to 53 μm.

[0049] In the present invention, the substrate is preheated before preparing the 420 martensitic stainless steel layer. For example, when the first layer is a 316L austenitic stainless steel layer, the substrate with the formed part of the component is preheated before preparing the next 420 martensitic stainless steel layer.

[0050] Exemplarily, the preheating temperature may be 100° C. to 180° C., such as 100° C., 120° C., 140° C., 160° C. or 180° C., or other values ​​within the range of 100° C. to 180° C. In some preferred embodiments, the preheating temperature is 120° C.

[0051] It should be noted that the inventors proposed that 420 martensitic stainless steel is prone to defects such as thermal cracks and pores during the laser additive manufacturing process. The present invention can greatly improve the quality of the 420 martensitic stainless steel layer by starting the substrate preheating function when additively manufacturing the 420 stainless steel layer and controlling the preheating temperature within the above range, while the substrate preheating function is not started when additively manufacturing the 316L stainless steel layer.

[0052] In powder-changing additive manufacturing, the powder for preparing the next stainless steel layer with a thickness not exceeding 0.02 mm is first laid on the surface of the previous stainless steel layer, and then the laser powder bed melting process is performed at least twice.

[0053] By controlling the pre-laying thickness of the prepared powder and then performing at least two passes of the laser powder bed melting process, it is helpful to ensure sufficient interface bonding strength.

[0054] In some optional embodiments, the process parameters of the laser powder bed melting process include: laser power of 150W to 400W, scanning speed of 500mm / s to 2500mm / s, scanning spacing of 0.06mm to 0.13mm, and powder thickness of 0.03mm to 0.05mm.

[0055] The laser power may be 150W, 200W, 250W, 300W, 350W or 400W, or other values ​​within the range of 150W to 400W.

[0056] The scanning speed may be 500 mm / s, 1000 mm / s, 1500 mm / s, 2000 mm / s or 2500 mm / s, or other values ​​within the range of 500 mm / s to 2500 mm / s.

[0057] The scanning interval may be 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.10 mm, 0.11 mm, 0.12 mm or 0.13 mm, etc., or other values ​​within the range of 0.06 mm to 0.13 mm.

[0058] The powder coating thickness can be 0.03 mm, 0.04 mm or 0.05 mm, etc., or other values ​​within the range of 0.03 mm to 0.05 mm.

[0059] By carrying out the laser powder bed melting process according to the above conditions, it is possible to achieve: 1) the thickness of each layer of 316L stainless steel layer and 420 stainless steel layer can be controlled; 2) the laser powder bed melting process parameters used for the same material stainless steel layer can be controlled; 3) the heat treatment process parameters of the layered composite plate can be controlled.

[0060] In addition, the above-mentioned laser powder bed melting process has the following advantages: 1) The solidification speed of the molten pool is extremely fast, the formed grains are small, and the mechanical properties are excellent; 2) The non-equilibrium metallurgical process can form new phases and realize the multi-phase composite reinforcement effect; 3) The forming process can be flexibly controlled by changing the process parameters, and is not restricted by the geometric shape of the formed component. In addition, the temperature gradient and surface tension gradient of the molten pool are large during the additive manufacturing process, the fluid movement in the molten pool is strong, and obvious diffusion behavior occurs, which can form a well-bonded interface.

[0061] It should be noted that the number of alternating additive manufacturing times or the thickness of each stainless steel layer can be adjusted according to actual needs, and there is no specific restriction on the order of setting 316L and 420.

[0062] Furthermore, the product obtained by additive manufacturing is heat treated.

[0063] In some optional embodiments, the heat treatment can be carried out at 500°C to 800°C (such as 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C, etc.) for 0.5h to 4h (such as 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h, etc.), followed by furnace cooling or air cooling.

[0064] In some preferred embodiments, the heat treatment is carried out at 600° C. for 2 hours, followed by furnace cooling or air cooling.

[0065] The microstructure of 316L stainless steel formed by laser powder bed fusion after heat treatment is still mainly composed of a large number of strip-shaped austenite structures. Austenite structures are clustered with high-density dislocation cells, mostly dislocation entanglements and cellular substructures. Clear large-angle cell boundaries and a large number of twins can also be observed, which makes the 316L stainless steel layer show high plasticity. The microstructure of 420 stainless steel formed by laser powder bed fusion after heat treatment is basically all martensitic structure, usually composed of cellular structures of several microns in size, and submicron-scale needle-shaped martensite is distributed in the cellular structure, which makes the 420 stainless steel layer show high strength, and thus makes the heterogeneous stainless steel layered composite plate have better plasticity and strength.

[0066] As mentioned above, the matching between the strength and plasticity of the heterogeneous stainless steel layered composite plate provided by the present invention can be controlled by selecting parameters such as the layered structure, the laser powder bed melting process, and the heat treatment process.

[0067] Accordingly, the present invention provides a heterogeneous stainless steel layered composite plate, which is prepared by the preparation method of any one of the aforementioned embodiments.

[0068] In the heterogeneous stainless steel layered composite plate, the interface between the 316L austenitic stainless steel and the 420 martensitic stainless steel is well metallurgically bonded.

[0069] In the 316L austenitic stainless steel layer of the heterogeneous stainless steel layered composite plate, the austenite structure is strip-shaped. High-density dislocation crystal cells are gathered on the austenite structure, wherein the high-density dislocation crystal cells include dislocation entanglements and cellular substructures. In addition, the microstructure of the above 316L austenitic stainless steel layer also has large-angle crystal cell boundaries and a large number of twins.

[0070] In the 420 martensitic stainless steel layer of the heterogeneous stainless steel layered composite plate, the microstructure includes a micrometer-scale cellular structure and submicrometer-scale needle-shaped martensite, and the submicrometer-scale needle-shaped martensite is distributed in the cellular structure.

[0071] In the heterogeneous stainless steel layered composite plate, the Ni element gradually decreases from the 316L stainless steel layer to the 420 stainless steel layer. In some optional embodiments, the Ni content of the 420 stainless steel layer 200 μm away from the interface (the bonding interface between the 316L stainless steel layer and the 420 stainless steel layer) is 2 wt% to 3 wt%.

[0072] In some optional embodiments, the heterogeneous stainless steel layered composite plate has a tensile strength of 1022 MPa to 1203 MPa, a yield strength of 873 MPa to 1052 MPa, and an elongation after fracture of 16.2% to 30.7%.

[0073] That is, the heterogeneous stainless steel layered composite plate provided by the present invention has the characteristics of both high strength and high toughness.

[0074] In addition, the present invention also provides a component, the raw materials for preparing the component include the above-mentioned heterogeneous stainless steel layered composite plate material.

[0075] The above-mentioned parts may exemplarily but not limitatively include parts for aerospace, automobiles or ships.

[0076] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0077] The 316L austenitic stainless steel powder and 420 martensitic stainless steel powder in the following examples and comparative examples are prepared by vacuum gas atomization, and the powder particle size is 15 μm to 53 μm, and the sphericity is good. The scanning electron microscope images thereof are shown as follows: Figure 2 and 3 shown.

[0078] The room temperature tensile mechanical properties of the stainless steel plates prepared in the following embodiments and comparative examples were tested according to standard GB / T 228.1-2021.

[0079] Example 1

[0080] This embodiment provides a heterogeneous stainless steel layered composite plate (layered structure is 316L stainless steel layer + 420 stainless steel layer, denoted as 316L / 420), the preparation method of which includes:

[0081] S1: Alternating additive manufacturing of 316L powder and 420 powder using laser powder bed fusion process.

[0082] S11: Place 316L powder in the laser powder bed melting equipment for additive manufacturing. The process parameters of the laser powder bed melting are: laser power of 275W, scanning speed of 1000mm / s, scanning spacing of 0.10mm, powder thickness of 0.05mm, and the stainless steel substrate is not preheated. The thickness of the 316L stainless steel layer formed by laser powder bed melting in this step is 6mm.

[0083] S12: Clean the 316L powder in the laser powder bed melting equipment, replace the 316L powder with 420 powder, adjust the position of the forming cylinder, pre-lay the 420 powder on the upper surface of the formed 316L stainless steel layer to a thickness of 0.018mm, preheat the stainless steel substrate to 120°C, and then perform laser melting forming twice. Among them, the process parameters of laser powder bed melting are: laser power of 275W, scanning speed of 700mm / s, scanning spacing of 0.13mm, and powder thickness of 0.05mm. The thickness of the 420 stainless steel layer formed by laser powder bed melting in this step is 6mm.

[0084] S2: The product obtained by additive manufacturing is kept at 600°C in a heat treatment furnace for 2 hours and then cooled in the furnace to obtain a heterogeneous stainless steel layered composite plate.

[0085] The scanning electron microscope image of the bonding interface of the heterogeneous stainless steel layered composite plate prepared in this example is as follows: Figure 4 As shown, the EDS energy spectrum scanning analysis diagram (Ni element) is as follows Figure 5 As shown, the EDS energy spectrum line scanning analysis diagram (Ni element) is as follows Figure 6 As shown. Figures 4 to 6 It can be seen that the interface metallurgical bonding of the heterogeneous stainless steel layered composite plate 316L / 420 prepared in this embodiment is good, and there are no obvious defects such as pores, thermal cracks, etc. At the same time, Ni, the element with the largest difference in chemical composition between 316L and 420 stainless steel, has obvious diffusion behavior, and its content gradually decreases from the high content of 316L stainless steel layer to 420 stainless steel layer, but the Ni content of 420 matrix can still reach 2wt% to 3wt% at about 200μm away from the interface.

[0086] The X-ray diffraction spectra of the 316L stainless steel layer and the 420 stainless steel layer in the heterogeneous stainless steel layered composite plate prepared in this embodiment are as follows: Figure 7 As shown. Figure 7 It can be seen that the microstructure of the 316L stainless steel layer in the heterogeneous stainless steel layer composite plate is a typical austenite structure, while the microstructure of the 420 stainless steel layer is a typical martensite structure.

[0087] The tensile engineering stress-strain curve of the heterogeneous stainless steel layered composite plate prepared in this example is as follows: Figure 8 As shown. Figure 8 It can be seen that the tensile strength of the heterogeneous stainless steel layered composite plate is 1146 MPa, the yield strength is 927 MPa, and the elongation after fracture is 19.8%.

[0088] The scanning electron microscope image of the tensile fracture of the heterogeneous stainless steel layered composite plate prepared in this example is as follows: Fig. 9 As shown. Fig. 9It can be seen that there are obvious differences in the tensile fracture morphologies of the 316L and 420 stainless steel layers in the heterogeneous stainless steel layered composite plate. The tensile fracture of the 316L stainless steel layer shows obvious ductile fracture characteristics and a large number of deep dimples, while the tensile fracture of the 420 stainless steel layer shows obvious brittle fracture characteristics, with obvious cracks and dissociation steps, and only a small number of shallow dimples.

[0089] Example 2

[0090] This embodiment provides a heterogeneous stainless steel layered composite plate (layered structure is 316L stainless steel layer + 420 stainless steel layer + 316L stainless steel layer + 420 stainless steel layer, denoted as 316L / 420 / 316L / 420), the preparation method of which includes:

[0091] S1: Alternating additive manufacturing of 316L powder and 420 powder using laser powder bed fusion process.

[0092] S11: Place 316L powder in the laser powder bed melting equipment for additive manufacturing. The process parameters of the laser powder bed melting are: laser power of 275W, scanning speed of 1000mm / s, scanning spacing of 0.10mm, powder thickness of 0.05mm, and the stainless steel substrate is not preheated. The thickness of the 316L stainless steel layer formed by laser powder bed melting in this step is 3mm.

[0093] S12: Clean the 316L powder in the laser powder bed melting equipment; replace the 316L powder with 420 powder, adjust the position of the forming cylinder, pre-lay the 420 powder on the upper surface of the formed 316L stainless steel layer with a thickness of 0.02mm, preheat the stainless steel substrate at a preheating temperature of 120°C, and then perform two passes of laser melting. Among them, the process parameters of laser powder bed melting are: laser power of 275W, scanning speed of 700mm / s, scanning spacing of 0.13mm, and powder thickness of 0.05mm. The thickness of the 420 stainless steel layer formed by laser powder bed melting in this step is 3mm.

[0094] S13: Clean the 420 powder in the laser powder bed melting equipment; replace the 420 powder with 316L powder, adjust the position of the forming cylinder, and pre-lay the 316L powder on the upper surface of the formed 420 stainless steel layer with a thickness of 0.10mm, and then perform two passes of laser melting (before additive manufacturing, the stainless steel substrate is not preheated). Among them, the process parameters of laser powder bed melting are: laser power of 275W, scanning speed of 700mm / s, scanning spacing of 0.13mm, and powder thickness of 0.05mm. The thickness of the 316L stainless steel layer formed by laser powder bed melting in this step is 3mm.

[0095] S14: Clean the 316L powder in the laser powder bed melting equipment again; replace the 316L powder with 420 powder, adjust the position of the forming cylinder, and pre-lay the 420 powder on the upper surface of the formed 316L stainless steel layer with a thickness of 0.18mm. Preheat the stainless steel substrate in advance at a preheating temperature of 120°C, and then perform laser melting forming twice. Among them, the process parameters of laser powder bed melting are: laser power of 275W, scanning speed of 700mm / s, scanning spacing of 0.13mm, and powder laying thickness of 0.05mm. The thickness of the 420 stainless steel layer formed by laser powder bed melting in this step is 3mm.

[0096] S2: The product obtained by additive manufacturing is kept at 600°C in a heat treatment furnace for 2 hours and then cooled in the furnace to obtain a heterogeneous stainless steel layered composite plate.

[0097] After testing, the heterogeneous stainless steel layered composite plate prepared in this embodiment has good interface metallurgical bonding, obvious diffusion behavior of elements, and a typical microstructure consisting of alternating austenite and martensite structures. The room temperature tensile strength is 1198MPa, the yield strength is 993MPa, and the elongation after fracture is 28.4.

[0098] Example 3

[0099] The difference between this embodiment and embodiment 2 is that the thickness of each 316L stainless steel layer is 4 mm, and the thickness of each 420 stainless steel layer is 2 mm.

[0100] After testing, the heterogeneous stainless steel layered composite plate prepared in this embodiment has good interface metallurgical bonding, obvious diffusion behavior of elements, and a typical microstructure consisting of alternating austenite and martensite structures. The room temperature tensile strength is 1087MPa, the yield strength is 909MPa, and the elongation after fracture is 30.7%.

[0101] Example 4

[0102] The difference between this embodiment and embodiment 2 is that the thickness of each 316L stainless steel layer is 2 mm, and the thickness of each 420 stainless steel layer is 4 mm.

[0103] After testing, the heterogeneous stainless steel layered composite plate prepared in this embodiment has good interface metallurgical bonding, obvious diffusion behavior of elements, and a typical microstructure consisting of alternating austenite and martensite structures. The room temperature tensile strength is 1203MPa, the yield strength is 1052MPa, and the elongation after fracture is 25.3%.

[0104] Example 5

[0105] This embodiment provides a heterogeneous stainless steel layered composite plate (layered structure is 316L stainless steel layer + 420 stainless steel layer + 316L stainless steel layer, denoted as 316L / 420 / 316L), the preparation method of which includes:

[0106] S1: Alternating additive manufacturing of 316L powder and 420 powder using laser powder bed fusion process.

[0107] S11: Place 316L powder in the laser powder bed melting equipment for additive manufacturing. The process parameters of the laser powder bed melting are: laser power of 400W, scanning speed of 2500mm / s, scanning spacing of 0.06mm, powder thickness of 0.04mm, and the stainless steel substrate is not preheated. The thickness of the 316L stainless steel layer formed by laser powder bed melting in this step is 4mm.

[0108] S12: Clean the 316L powder in the laser powder bed melting equipment; replace the 316L powder with 420 powder, adjust the position of the forming cylinder, and pre-lay the 420 powder on the upper surface of the formed 316L stainless steel layer with a thickness of 0.18mm. Preheat the stainless steel substrate in advance at a preheating temperature of 120°C, and then perform two passes of laser melting. Among them, the process parameters of laser powder bed melting are: laser power of 275W, scanning speed of 700mm / s, scanning spacing of 0.13mm, and powder thickness of 0.05mm. The thickness of the 420 stainless steel layer formed by laser powder bed melting in this step is 4mm.

[0109] S13: Clean the 420 powder in the laser powder bed melting equipment; replace the 420 powder with 316L powder, adjust the position of the forming cylinder, control the thickness of the 316L powder pre-laid on the upper surface of the formed 420 stainless steel layer to 0.02mm, and then perform two passes of laser melting (before additive manufacturing, the stainless steel substrate is not preheated). Among them, the process parameters of laser powder bed melting are: laser power of 400W, scanning speed of 2500mm / s, scanning spacing of 0.06mm, and powder thickness of 0.04mm. The thickness of the 316L stainless steel layer formed by laser powder bed melting in this step is 4mm.

[0110] S2: The product obtained by additive manufacturing is kept at 800°C in a heat treatment furnace for 0.5h and then cooled in the furnace to obtain a heterogeneous stainless steel layered composite plate.

[0111] After testing, the heterogeneous stainless steel layered composite plate prepared in this embodiment has good interface metallurgical bonding, obvious diffusion behavior of elements, and a typical microstructure consisting of alternating austenite and martensite structures. The room temperature tensile strength is 1022MPa, the yield strength is 873MPa, and the elongation after fracture is 24.6%.

[0112] Example 6

[0113] This embodiment provides a heterogeneous stainless steel layered composite plate (layered structure is 420 stainless steel layer + 316L stainless steel layer + 420 stainless steel layer, denoted as 420 / 316L / 420), the preparation method of which includes:

[0114] S1: Alternate additive manufacturing of 420 powder and 316L powder using laser powder bed fusion process.

[0115] S11: Place 420 powder in the laser powder bed melting equipment for additive manufacturing. The process parameters of laser powder bed melting are: laser power of 150W, scanning speed of 500mm / s, scanning spacing of 0.13mm, and powder thickness of 0.03mm. Before additive manufacturing, the substrate is preheated at 120°C. The thickness of the 420 stainless steel layer formed by laser powder bed melting in this step is 4mm.

[0116] S12: Clean the 420 powder in the laser powder bed melting equipment; replace the 420 powder with 316L powder, adjust the position of the forming cylinder, and pre-lay the 316L powder on the upper surface of the formed 420 stainless steel layer with a thickness of 0.08mm, and then perform two passes of laser melting (before additive manufacturing, the stainless steel substrate is not preheated). Among them, the process parameters of laser powder bed melting are: laser power of 275W, scanning speed of 1000mm / s, scanning spacing of 0.10mm, and powder thickness of 0.05mm. The thickness of the 316L stainless steel layer formed by laser powder bed melting in this step is 4mm.

[0117] S13: Clean the 316L powder in the laser powder bed melting equipment; replace the 316L powder with 420 powder, adjust the position of the forming cylinder, and pre-lay the 420 powder on the upper surface of the formed 316L powder stainless steel layer with a thickness of 0.18mm. Preheat the stainless steel substrate in advance at a preheating temperature of 120°C, and then perform laser melting forming twice. Among them, the process parameters of laser powder bed melting are: laser power of 150W, scanning speed of 500mm / s, scanning spacing of 0.13mm, and powder laying thickness of 0.03mm. The thickness of the 420 stainless steel layer formed by laser powder bed melting in this step is 4mm.

[0118] S2: The product obtained by additive manufacturing is kept at 500°C in a heat treatment furnace for 4 hours and then cooled to obtain a heterogeneous stainless steel layered composite plate.

[0119] After testing, the heterogeneous stainless steel layered composite plate prepared in this embodiment has good interface metallurgical bonding, obvious diffusion behavior of elements, and a typical microstructure consisting of alternating austenite and martensite structures. The room temperature tensile strength is 1088MPa, the yield strength is 916MPa, and the elongation after fracture is 16.2%.

[0120] Comparative Example 1

[0121] This comparative example provides a 316L stainless steel plate, the preparation method of which includes:

[0122] S1: Place 316L powder in the laser powder bed melting equipment for additive manufacturing. The process parameters of laser powder bed melting are: laser power of 275W, scanning speed of 1000mm / s, scanning spacing of 0.10mm, powder thickness of 0.05mm, and substrate is not preheated. The thickness of the 316L stainless steel layer formed by laser powder bed melting in this step is 12mm.

[0123] S2: The product obtained by additive manufacturing is kept at 600°C in a heat treatment furnace for 2 hours and then cooled in the furnace to obtain a heterogeneous stainless steel layered composite plate.

[0124] After testing, the microstructure of the 316L stainless steel plate prepared in this comparative example is a typical austenite structure, with a room temperature tensile strength of 712 MPa, a yield strength of 534 MPa, and an elongation after fracture of 40.3%.

[0125] Comparative Example 2

[0126] This comparative example provides a 420 stainless steel plate, the preparation method of which includes:

[0127] S1: Place 420 powder in the laser powder bed melting equipment for additive manufacturing. The process parameters of laser powder bed melting are: laser power of 275W, scanning speed of 700mm / s, scanning spacing of 0.13mm, and powder thickness of 0.05mm. Before preparation, preheat the substrate at 120℃. The thickness of the 420 stainless steel layer formed by laser powder bed melting in this step is 12mm.

[0128] S2: The product obtained by additive manufacturing is kept at 600°C in a heat treatment furnace for 2 hours and then cooled in the furnace to obtain a heterogeneous stainless steel layered composite plate.

[0129] After testing, the microstructure of the 420 stainless steel plate prepared in this comparative example is a typical martensitic structure, with a room temperature tensile strength of 1517 MPa, a yield strength of 1246 MPa, and an elongation after fracture of 11.1%.

[0130] Comparative Example 3

[0131] The difference between this comparative example and Example 1 is that the substrate is not preheated before preparing the 420 martensitic stainless steel layer.

[0132] After testing, the interface metallurgical bonding of the heterogeneous stainless steel layered composite plate prepared in this comparative example is general, there are obvious defects such as small holes at the 316L / 420 interface, and there are obvious defects such as cracks in the 420 martensitic stainless steel layer. The elements have obvious diffusion behavior, and the microstructure is a typical alternation of austenite and martensite structures. The room temperature tensile strength is 641MPa, the yield strength is 435MPa, and the elongation after fracture is 9.4%.

[0133] Comparative Example 4

[0134] The difference between this comparative example and Example 1 is that during powder-changing additive manufacturing, the thickness of the powder prepared for the next stainless steel layer first laid on the surface of the previous stainless steel layer is 0.05 mm.

[0135] After testing, the interface metallurgical bonding of the heterogeneous stainless steel layered composite plate prepared in this comparative example is general, there are a small amount of unfused defects at the 316L / 420 interface, the elements have obvious diffusion behavior, and the microstructure is a typical alternation of austenite and martensite structures. The room temperature tensile strength is 876MPa, the yield strength is 598MPa, and the elongation after fracture is 13.2%.

[0136] Comparative Example 5

[0137] The difference between this comparative example and Example 1 is that the heat treatment temperature in step S2 is 900°C.

[0138] After testing, the heterogeneous stainless steel layered composite plate prepared in this comparative example has good interface metallurgical bonding, obvious diffusion behavior of elements, and a typical microstructure consisting of alternating austenite and martensite structures. The room temperature tensile strength is 658MPa, the yield strength is 423MPa, and the elongation after fracture is 28.7%.

[0139] The room temperature tensile mechanical properties of the stainless steel plates prepared in the above embodiments and comparative examples are summarized in Table 1.

[0140] Table 1 Performance test results

[0141]

[0142] It can be seen from Table 1 that the room temperature tensile strength of the heterogeneous stainless steel layered composite sheet obtained in Examples 1 to 6 of the present invention is 1022 to 1203 MPa, the yield strength is 873 to 1052 MPa, and the elongation after fracture is 16.2 to 30.7%. The three indicators are between the 316L stainless steel sheet obtained in Comparative Example 1 and the 420 stainless steel sheet obtained in Comparative Example 2, taking into account the high plasticity of the 316L austenitic stainless steel material and the high strength of the 420 martensitic stainless steel material, and it can be used for key parts such as aerospace, automobiles, and ships.

[0143] By comparing Example 1 and Comparative Example 3, it can be seen that whether the substrate is preheated before preparing the 420 martensitic stainless steel layer will affect the defects in the 420 martensitic stainless steel layer, and further significantly affect the comprehensive mechanical properties of the composite plate.

[0144] By comparing Example 1 and Comparative Example 4, it can be seen that during powder-changing additive manufacturing, whether the thickness of the powder prepared by pre-laying the subsequent stainless steel layer on the surface of the previous stainless steel layer is appropriate will affect the comprehensive mechanical properties of the composite plate.

[0145] By comparing Example 1 and Comparative Example 5, it can be seen that the control of the heat treatment temperature in step S2 will also affect the comprehensive mechanical properties of the composite board.

[0146] In summary, the 316L / 420 heterogeneous interface prepared by adjusting the laser powder bed melting process parameters in the present invention presents good metallurgical bonding; by adjusting the layered structure parameters, the respective advantages of 316L austenitic stainless steel and 420 martensitic stainless steel are fully utilized; and then the microstructure of 316L austenitic stainless steel and 420 martensitic stainless steel is adjusted through a suitable heat treatment process, and the further diffusion of elements can be promoted, and finally a controllable layered structure is formed. The prepared high-strength and tough heterogeneous stainless steel composite plate can be applied to key parts such as aerospace, automobiles, and ships.

[0147] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a heterogeneous stainless steel layered composite plate, characterized in that: The following steps are involved: The 316L powder and the 420 powder are alternately additively manufactured by a laser powder bed fusion process to obtain a heterogeneous stainless steel layered composite plate consisting of alternating 316L austenitic stainless steel layers and 420 martensitic stainless steel layers; Wherein, before preparing the 420 martensitic stainless steel layer, the substrate is preheated; In powder-changing additive manufacturing, the powder for preparing the next stainless steel layer with a thickness not exceeding 0.02 mm is first laid on the surface of the previous stainless steel layer, and then the laser powder bed melting process is performed at least twice.

2. The preparation method according to claim 1, characterized in that: The process parameters of the laser powder bed fusion process include: laser power of 150W to 400W, scanning speed of 500mm / s to 2500mm / s, scanning spacing of 0.06mm to 0.13mm, and powder thickness of 0.03mm to 0.05mm.

3. The preparation method according to claim 1, characterized in that: The 316L powder and the 420 powder are independently prepared by a powder preparation method; Preferably, the powder preparation method is a vacuum air atomization method; Preferably, the particle sizes of the 316L powder and the 420 powder are independently 15 μm to 53 μm.

4. The preparation method according to any one of claims 1 to 3, characterized in that: Also includes: heat treating the product obtained by additive manufacturing; Preferably, the heat treatment is carried out at 500°C to 800°C for 0.5h to 4h, followed by furnace cooling or air cooling; More preferably, the heat treatment is carried out at 600° C. for 2 hours, followed by furnace cooling or air cooling.

5. A heterogeneous stainless steel layered composite plate, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 4.

6. The heterogeneous stainless steel layered composite sheet according to claim 5, characterized in that: The austenite structure in the 316L austenitic stainless steel layer is in strip shape; Preferably, a high density of dislocation cells are gathered on the austenite structure; Preferably, the high-density dislocation unit cell includes dislocation tangles and cellular substructures; Preferably, the microstructure of the 316L austenitic stainless steel layer also contains large-angle unit cell boundaries and a large number of twins.

7. The heterogeneous stainless steel layered composite sheet according to claim 5, characterized in that: The microstructure of the 420 martensitic stainless steel layer includes a micrometer-scale cellular structure and submicrometer-scale needle-shaped martensite, and the submicrometer-scale needle-shaped martensite is distributed in the cellular structure.

8. The heterogeneous stainless steel layered composite sheet according to claim 5, characterized in that: In the heterogeneous stainless steel layered composite plate, the Ni element gradually decreases from the 316L stainless steel layer to the 420 stainless steel layer; Preferably, the Ni content of the 420 stainless steel layer at 200 μm away from the interface is 2 wt% to 3 wt%; Preferably, the interface between the 316L austenitic stainless steel and the 420 martensitic stainless steel is well metallurgically bonded.

9. The heterogeneous stainless steel layered composite sheet according to any one of claims 5 to 8, characterized in that: The heterogeneous stainless steel layered composite plate has a tensile strength of 1022MPa to 1203MPa, a yield strength of 873MPa to 1052MPa, and an elongation after fracture of 16.2% to 30.7%.

10. A component, characterized in that: The raw materials for preparing the parts include the heterogeneous stainless steel layered composite plate material as described in any one of claims 5 to 9; Preferably, the parts include parts for aerospace, automobile or shipbuilding.

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