Mechanical property testing method of WC-316L composite material
Through laser melt deposition, electric spark cutting and universal testing machine testing, combined with SEM analysis, a systematic mechanical properties testing method of WC-316L composite materials is provided, which solves the problem of incomplete testing methods in the existing technology, improves the repeatability and data consistency of the test, reveals the multi-scale performance and fracture mechanism of the material, and promotes the design and optimization of composite materials.
Patent Information
- Application Number
- CN202510711030.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-29
- Publication Date
- 2025-08-12
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
The prior art lacks systematic and standardized mechanical properties testing methods, making it difficult to evaluate the true performance of WC-316L composite materials, and 316L stainless steel is prone to failure when used in high-strength and high-wear environments.
Multi-layer deposition samples were prepared by laser melting deposition equipment, and the samples were cut using an electric spark wire cutting machine. Tensile test was performed at room temperature through a universal test machine, cross beam displacement and load stress were recorded, combined with SEM fracture morphology analysis, stress-strain curves were calculated, and different scanning directions and strain rates were considered.
It provides a systematic and comprehensive test method, improves the repeatability and data consistency of the experiment, can characterize the multi-scale performance of composite materials, supports comparative testing of different material combinations, reveals the impact of laser deposition direction on performance, simulates different service environments, and deeply understands the fracture mechanism based on microscopic analysis.
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Figure CN120467897A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of material performance testing, and in particular to a method for testing the mechanical properties of a WC-316L composite material. Background Art
[0002] With the continuous advancement of industrial technology, high-performance metal materials are playing an increasingly important role in key areas such as aerospace, medical devices, and energy equipment. 316L austenitic stainless steel is widely used in additive manufacturing (i.e., 3D printing) due to its excellent corrosion resistance, superior weldability, and biocompatibility. However, due to its low hardness and poor wear resistance, it is prone to failure in certain high-intensity, high-wear environments, limiting its wider application.
[0003] To address these issues, researchers have recently begun experimenting with reinforcing 316L stainless steel by introducing high-hardness particles. Tungsten carbide (WC) is considered an ideal reinforcement due to its exceptional hardness, excellent wear resistance, and thermal stability. Adding WC particles to a 316L matrix to form a composite material is expected to significantly improve the mechanical properties, particularly tensile strength and wear resistance, while maintaining the stainless steel's inherent properties.
[0004] Although preliminary research has demonstrated the feasibility of WC particle reinforcement of 316L stainless steel, practical applications still face numerous challenges. For example, precisely controlling laser deposition parameters to achieve a uniformly distributed composite structure is crucial; the effects of varying particle size, ratio, and scanning direction on material properties remain unclear; and there is a lack of systematic and standardized mechanical testing methods to evaluate the true performance of such composites.
[0005] Therefore, there is an urgent need for a scientific and repeatable mechanical property testing method to guide the design and optimization of WC-316L composite materials and promote their widespread application in engineering practice. Summary of the Invention
[0006] The object of the present invention is to provide a method for testing the mechanical properties of WC-316L composite materials to solve the above-mentioned defects caused by the prior art.
[0007] A method for testing the mechanical properties of WC-316L composite materials includes the following testing steps:
[0008] S1: Each WC-316L composite material was deposited using a laser melting deposition device to prepare multilayer deposition samples of the same size;
[0009] S2: Use wire-cut electric discharge machine to cut each multilayer deposited sample;
[0010] S3: Under room temperature conditions, a universal testing machine is used to perform a tensile test on each prepared multilayer deposition specimen. During the test, the beam displacement and the corresponding load stress of the universal testing machine after the load is stretched are recorded;
[0011] S4: Based on the recorded data, the stress-strain curve corresponding to each multilayer deposition sample is calculated.
[0012] Preferably, the laser power of the laser melting deposition equipment is 1.5 kW, the scanning speed is 10 mm / s, and the powder feeding rate is 6.8 g / min.
[0013] Preferably, the WC-316L composite material includes the following four types: ①316L; ②8wt.% coarse WC-316L; ③8wt.% fine WC-316L; ④(4wt.% coarse WC+4wt.% fine WC)-316L.
[0014] Preferably, each WC-316L composite material is deposited in two scanning directions, horizontal and vertical.
[0015] Preferably, the size of each multi-layer deposition sample is 45 mm×75 mm×5 mm, the thickness of each layer is 1 mm, and the overlap rate is 50%.
[0016] Preferably, during the test, the strain rates used include the following three: 0.001s -1 , 0.01s -1 , 0.1s -1 .
[0017] Preferably, after the test is completed, the fracture morphology of each multi-layer deposition sample after being stretched is photographed using SEM.
[0018] Compared with the prior art, the present invention has the following advantages:
[0019] 1. The testing method is systematic and comprehensive:
[0020] This method covers the entire process from sample preparation to mechanical testing to microscopic analysis, and can fully characterize the multi-scale properties of composite materials from macroscopic mechanical response to microscopic fracture behavior.
[0021] 2. Strong controllability of process parameters:
[0022] The specific process parameters of the laser melting deposition equipment (such as power, scanning speed, and powder feeding rate) are clearly set, which helps to improve the repeatability of the experiment and the consistency of the data.
[0023] 3. Suitable for comparison of multiple material combinations:
[0024] The method supports comparative testing of different types of WC-316L composites (including pure 316L, coarse / fine WC single doping or mixed doping), which is conducive to screening the best reinforcement scheme.
[0025] 4. Consider the influence of material anisotropy:
[0026] In particular, the introduction of horizontal and vertical deposition directions for comparative testing helps to reveal the influence of laser deposition direction on the mechanical properties of composite materials.
[0027] 5.Multi-strain rate test conditions:
[0028] Provide three different strain rates (0.001s -1 , 0.01s -1 , 0.1s -1 ) can simulate the loading conditions in different service environments and improve the actual reference value of the test results.
[0029] 6. Combined with micro-analysis methods:
[0030] SEM fracture morphology analysis after tensile testing helps to gain a deeper understanding of the material's fracture mechanism and its relationship with the microstructure.
[0031] 7. Promote composite material design and optimization:
[0032] This method can not only be used to evaluate the performance of existing materials, but also serve as a standard testing process in the research and development of new WC-reinforced metal matrix composites, laying a solid foundation for subsequent industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Figure 1 This is a flow chart of the mechanical property testing of four WC-316L composite materials in the present invention.
[0034] Figure 2 Process diagram of laser melting deposition of four WC-316L composite materials and preparation of multilayer deposition specimens.
[0035] Figure 3 Macromorphology of each multilayer deposition sample prepared using four WC-316L composite materials.
[0036] Figure 4 The macroscopic morphology of each multilayer deposition sample after tensile testing.
[0037] Figure 5 The stress-strain curves of each multilayer deposition sample prepared at different strain rates.
[0038] Figure 6The fracture macromorphology of each multilayer deposition sample after stretching.
[0039] Figure 7 The fracture morphology of each multilayer deposition sample after stretching.
[0040] Figure 8 This is a schematic diagram showing the principle of dimple formation when metal materials are stretched. DETAILED DESCRIPTION
[0041] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.
[0042] like Figure 1 As shown, a mechanical property testing method for WC-316L composite material includes the following testing steps:
[0043] S1: Each WC-316L composite material was deposited using a laser melting deposition device to prepare multilayer deposition samples of the same size;
[0044] S2: Use wire-cut electric discharge machine to cut each multilayer deposited sample;
[0045] S3: Under room temperature conditions, a universal testing machine is used to perform a tensile test on each prepared multilayer deposition specimen. During the test, the beam displacement and the corresponding load stress of the universal testing machine after the load is stretched are recorded;
[0046] S4: Based on the recorded data, the stress-strain curve corresponding to each multilayer deposition sample is calculated.
[0047] In this embodiment, the laser power of the laser melting deposition equipment is 1.5 kW, the scanning speed is 10 mm / s, and the powder feeding rate is 6.8 g / min.
[0048] In this embodiment, the WC-316L composite materials include the following four types: ①316L; ②8wt.% coarse WC-316L; ③8wt.% fine WC-316L; ④(4wt.% coarse WC+4wt.% fine WC)-316L.
[0049] In this embodiment, each WC-316L composite material is deposited in two scanning directions, horizontal and vertical.
[0050] In this embodiment, the size of each multi-layer deposition sample is 45 mm×75 mm×5 mm, the thickness of each layer is 1 mm, and the overlap rate is 50%.
[0051] In this embodiment, during the test, the strain rates used include the following three: 0.001s-1 , 0.01s -1 , 0.1s -1 . In order to study the effect of different strain rates on the tensile properties of materials.
[0052] In this embodiment, after the test is completed, the fracture morphology of each multi-layer deposition sample after being stretched is photographed using SEM.
[0053] like Figure 2 As shown, a process diagram of "using laser melting deposition equipment to deposit each WC-316L composite material to prepare multi-layer deposition samples of the same size" is shown.
[0054] like Figure 3 As shown in the figure, the macroscopic morphology of the multilayer deposited sample obtained by "depositing each WC-316L composite material in horizontal and vertical scanning directions" is shown. It can be seen from the figure that the surface of the multilayer deposited sample is relatively flat, showing a metallic luster, and the overlapping parts are clearly visible.
[0055] like Figure 4 As shown in the figure, "tensile test was performed on each prepared multilayer deposition sample using a universal testing machine", and the macroscopic morphology of the obtained multilayer deposition sample after fracture was shown, wherein: the samples in Figure a and Figure b were obtained by depositing pure 316L in the vertical and horizontal scanning directions; the samples in Figure c and Figure d were obtained by depositing 8wt.% coarse WC-316L in the vertical and horizontal scanning directions; the samples in Figure e and Figure f were obtained by depositing 8wt.% fine WC-316L in the vertical and horizontal scanning directions; the samples in Figure g and Figure h were obtained by depositing (4wt.% coarse WC + 4wt.% fine WC)-316L in the vertical and horizontal scanning directions.
[0056] like Figure 5 As shown in the figure, the stress-strain curve change trends of the same composite material in the same direction are basically the same, and the overall trend is to first rise and then fall. At the beginning of stretching, the stress-strain curve rises rapidly, which is because the material is in the elastic deformation stage. Subsequently, the curve rises slowly and enters the plastic deformation range until the curve reaches the highest point, indicating that the sample has reached the tensile limit. Subsequently, the curve drops sharply, and the sample breaks at this time. By comparing the stress-strain curves of four different materials, the mechanical properties of the sample obtained by transverse deposition are better. This may be because the overlap length of each time the material is transversely deposited is shorter, the organizational structure is more uniform, and the defects and heterogeneity in the material are reduced; at the same time, transverse deposition may lead to lower residual stress. This is because the change in deposition direction may reduce the thermal stress during the preparation process or the internal stress caused by cooling. The short transverse deposition path helps to slow down the accumulation of thermal stress and reduce the formation of internal defects.
[0057] The test data are as follows: Table 1 is the tensile data of 316L longitudinal and transverse deposition samples, Table 2 is the tensile data of 8wt.% coarse WC-316L longitudinal and transverse deposition samples, Table 3 is the tensile data of 8wt.% fine WC-316L longitudinal and transverse deposition samples, and Table 4 is the tensile data of (4wt.% coarse WC + 4wt.% fine WC)-316L longitudinal and transverse deposition samples.
[0058] Table 1 Tensile data of 316L longitudinal and transverse deposition specimens
[0059]
[0060] Table 2 Tensile data of 8wt.% coarse WC-316L longitudinal and transverse deposition samples
[0061]
[0062]
[0063] Table 3 Tensile data of 8wt.% fine WC-316L longitudinal and transverse deposition specimens
[0064]
[0065] Table 4 (4wt.% coarse WC + 4wt.% fine WC) - tensile data of 316L longitudinal and transverse deposition samples
[0066]
[0067] By comparing the tensile data in the four tables, the introduction of WC improves the mechanical tensile properties compared to pure materials. The four different materials 316L, 8wt.% coarse WC-316L, 8wt.% fine WC-316L, (4wt.% coarse WC + 4wt.% fine WC)-316L, and the corresponding transverse average tensile strengths at three tensile speeds are 916Mpa, 959Mpa, 977Mpa, and 929Mpa, respectively. Compared to pure materials, the tensile strengths of the other three materials are increased by 4.7%, 6.7%, and 1.4%, respectively. Due to the introduction of WC of different sizes, the distribution of WC in the material is more uniform. The grains grown around the WC increase the hardness of the material. At the same time, WC has a certain effect on grain refinement, which improves the tensile properties of the material.
[0068] In order to study the fracture mechanism of different materials, SEM was used to shoot the fracture morphology after stretching. Figure 6 and Figure 7 , Figure 6 The macroscopic morphology of the fracture of four different materials is shown in Figure 2. Figure 7Figures a1-a3 show the fracture morphology of pure 316L material, b1-b3 show 8wt.% coarse WC-316L, c1-c3 show 8wt.% fine WC-316L, and d1-d3 show (4wt.% coarse WC + 4wt.% fine WC)-316L. a1-d1 are longitudinal tensile specimens, a2-d2 are transverse tensile specimens, and a3-d3 are fracture morphologies at high magnification. WC of different scales is indicated in the figure. During the tensile process, the surface unevenness is mainly caused by surface inclusions and surface defects, slip bands formed on the surface by crystal plane slip, and wrinkles formed at the grain boundaries due to grain rotation. Due to the uneven density of the material caused by solidification defects, cracks are easily generated during the tensile deformation process, causing stress concentration and ultimately leading to material failure. As can be seen from the figure, there is a necking phenomenon at the fracture surface, and the coarse WC breaks during the tensile process. At the same time, dimples can be observed in the SEM image. The fracture mode of the specimen is ductile fracture. Compared with pure 316L material, no pores are formed in the sample with WC added, which has a certain effect on improving the material performance. Through the solid solution strengthening effect, WC is wrapped in the solid solution, and the dislocation barrier improves the material's deformation resistance. WC also refines the grains and makes the material structure more uniform, which has the ability to withstand forces in all directions. Figure 7 In b1, we can see the pores after WC peeling, which is caused by the rapid cooling of the molten pool and the relatively slow fluidity of the molten pool during the laser melting deposition process.
[0069] When a metal tensile test is performed on a tensile part, as the external force gradually increases, the tensile material will fracture. Fracture is a multi-stage process involving nucleation, diffusion and convergence of cracks and voids. Fracture can be divided into ductile fracture and brittle fracture. Ductile fracture is usually associated with necking and mediated by dislocation activity. It involves relatively slow void nucleation, growth and aggregation, so the formation of dimples can be observed on the fracture surface. The principle diagram of dimple generation is shown in the figure below. Figure 8 As shown in Figure 2, the necking of the material leads to the formation of dimples. When the material is subjected to tension, the rapid extension caused by the load causes the specimen to undergo plastic deformation, rapidly reducing the load-applied area and ultimately creating small voids. After necking, stress concentration and the rapid nucleation, growth, and aggregation of voids in the neck region lead to rapid ductile fracture.
[0070] The dimples in the fracture morphology are also closely related to the grain size. When the grain size is small, the dislocation sources inside the grains are reduced. Normally, dislocations are mainly generated at the grain boundaries, then pass through the grains and disappear at the grain boundaries, without accumulating within the grains. Due to the small grain size and the existence of grain boundary effects, the strain hardening rate in nanomaterials is usually low, even close to 0. Therefore, necking usually occurs at lower strains, resulting in low uniform ductility of the material. In coarse-grained materials, dislocations are usually generated at traditional dislocation sources, and as the plastic strain increases, these dislocations are effectively accumulated at dislocation cells and subgrain boundaries.
[0071] The grain refinement caused by WC has a certain influence on the mechanical tensile properties of the material. There is a certain relationship between the yield strength and the grain size of the material, which conforms to the Hall-Petch rule, as shown in formula (1-1)
[0072] YS=τ0+kD -1 / 2 (1-1)
[0073] Where YS is the yield strength of the material, D is the grain size, τ0 and k are linear fitting parameters.
[0074] According to formula (1-1), as the grain size decreases, the yield strength of the material will be improved. During the stretching process, the grains will produce dislocation movement, and the grain boundaries will hinder the slip and dislocation of the grains. When WC is introduced, the phase space increases, the grain boundary density increases, and the grain size of the material is refined, which ultimately improves the mechanical properties of the material.
[0075] In summary, this paper mainly studies the longitudinal and transverse tensile properties of four multilayer specimens: 316L, fine WC-316L, coarse WC-316L, and (coarse WC + fine WC)-316L. The main conclusions are as follows:
[0076] (1) By comparing the stress-strain curves of four different materials, the mechanical properties of the samples obtained by transverse deposition are better. This is because the overlap length of the material is shorter each time during transverse deposition, the microstructure is more uniform, and the defects and heterogeneity in the material are reduced.
[0077] (2) Four different materials: 316L, 8wt.% coarse WC-316L, 8wt.% fine WC-316L, (4wt.% coarse WC + 4wt.% fine WC)-316L, the corresponding average transverse tensile strengths at three tensile speeds are 916 MPa, 959 MPa, 977 MPa, and 929 MPa, respectively. Compared with the pure material, the tensile strength of the other three materials increased by 4.7%, 6.7%, and 1.4%, respectively.
[0078] Therefore, the embodiments disclosed above are only illustrative in all aspects and are not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are encompassed by the present invention.
Claims
1. A method for testing the mechanical properties of WC-316L composite materials, characterized in that: The test steps include: S1: Each WC-316L composite material was deposited using a laser melting deposition device to prepare multilayer deposition samples of the same size; S2: Use wire-cut electric discharge machine to cut each multilayer deposited sample; S3: Under room temperature conditions, a universal testing machine is used to perform a tensile test on each prepared multilayer deposition specimen. During the test, the beam displacement and the corresponding load stress of the universal testing machine after the load is stretched are recorded; S4: Based on the recorded data, the stress-strain curve corresponding to each multilayer deposition sample is calculated.
2. The mechanical properties testing method of a WC-316L composite material according to claim 1, characterized in that: The laser power of the laser melting deposition equipment is 1.5kW, the scanning speed is 10mm / s, and the powder feeding rate is 6.8g / min.
3. The mechanical properties testing method of a WC-316L composite material according to claim 1, characterized in that: The WC-316L composite materials include the following four types: ①316L; ②8wt.% coarse WC-316L; ③8wt.% fine WC-316L; ④(4wt.% coarse WC+4wt.% fine WC)-316L.
4. The mechanical properties testing method of a WC-316L composite material according to claim 1, characterized in that: Each WC-316L composite material was deposited in two scanning directions: horizontal and vertical.
5. The mechanical properties testing method of a WC-316L composite material according to claim 1, characterized in that: The size of each multilayer deposition sample is 45 mm × 75 mm × 5 mm, the thickness of each layer is 1 mm, and the overlap rate is 50%.
6. The mechanical properties testing method of a WC-316L composite material according to claim 1, characterized in that: During the test, the strain rates used include the following three: 0.001s -1 , 0.01s -1 , 0.1s -1 .
7. The mechanical properties testing method of a WC-316L composite material according to claim 1, characterized in that: After the test, the fracture morphology of each multilayer deposition sample after stretching was photographed using SEM.