A device and method for evaluating crack resistance of laser cladding materials

Abstract

The present invention discloses a device and method for evaluating the crack resistance of laser cladding materials. The device includes a test plate, the test plate is provided with a slit, and the test plate and a backing plate are fixed by anchors on both sides of the slit with the slit as the symmetry axis; the surface of the slit is covered with a cladding layer. The method is as follows: first, a slit is cut at one end of the test plate, holes are symmetrically punched on both sides of the slit with the slit as the symmetry axis, the test plate is fixed to the backing plate by bolts, and then metal powder is laser clad along the slit to form a continuous cladding layer; the crack length on the surface of the cladding layer and the total length of the cladding layer are measured, the crack rate is calculated, and the crack resistance of the cladding metal powder material is evaluated. The present invention only needs to use bolts to fix the test plate and the backing plate. The method is simple to operate, the constraint degree can be flexibly adjusted, the crack rate calculation is simple, the test results are reliable and effective, and can be used to evaluate the crack resistance of laser cladding materials under various conditions.

Description

Technical Field

[0001] The present invention relates to a device and method for evaluating laser cladding, and in particular to a device and method for evaluating the crack resistance of laser cladding materials. Background Art

[0002] Laser cladding technology is a new green surface technology that uses a high-energy-density laser beam to melt and deposit the cladding material together with the substrate surface, forming a metallurgical bond between the substrate surface and the cladding material to achieve the purpose of repair and strengthening. Compared with traditional surface strengthening and repair technologies, laser cladding technology has a low substrate dilution rate. Under the action of the laser, the substrate and the cladding layer achieve a good metallurgical bond, with a bonding strength that cannot be achieved by traditional technologies. At the same time, laser cladding technology has a faster heating and cooling rate, which is conducive to the formation of fine grains and greatly improves the strength and wear resistance of the cladding layer. However, rapid heating and cooling will generate large stresses during the solidification process, and the cladding layer is prone to cracks, resulting in failure of the cladding layer and difficulty in achieving the surface strengthening effect. Cracks have become a major issue hindering the development and application of laser cladding technology. Therefore, it is crucial to develop a reliable and effective method for evaluating the crack resistance of laser cladding materials.

[0003] CN114279785 discloses a method for evaluating the crack resistance of laser cladding coatings. The method involves providing a test specimen with a slot structure comprising a circular arc-shaped groove and a longitudinal channel. Laser cladding is used to clad metal powder over the arc-shaped groove to form a coating. After cladding, the crack rates of the coatings are measured and compared to evaluate the crack resistance of the different coatings. However, this technique has the disadvantages of complex slot structures, making machining difficult. Furthermore, the arc-shaped grooves used in this technique predominately require flat cladding in actual production, making it difficult to apply to actual cladding conditions.

[0004] CN105506615 discloses a method for controlling the microstructure and thermal crack sensitivity of laser cladding coatings. This method changes the incident angle of the laser during the laser cladding process, thereby changing the microstructure and growth orientation of the cladding layer, thereby changing the resistance of the cladding layer to thermal cracking, thereby achieving the purpose of controlling the formation of thermal cracks in the cladding. After the cladding is completed, the thermal crack sensitivity is evaluated by comparing the total crack length per unit cross-sectional area of ​​the cladding coating. However, this technology requires the preparation of metallographic samples after the cladding is completed to calculate the total crack length per unit cross-sectional area of ​​the cladding coating. This statistical process is relatively cumbersome and time-consuming. Summary of the Invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a device for evaluating the crack resistance of laser cladding materials with simple operation and high reliability;

[0006] A second object of the present invention is to provide a method for evaluating the crack resistance of laser cladding materials using the above-mentioned apparatus.

[0007] Technical solution: The device for evaluating the crack resistance of laser cladding materials described in the present invention includes a test plate with a gap provided on it. The test plate and the backing plate are fixed to each other by anchors on both sides of the gap with the gap as the axis of symmetry; the surface of the gap is covered with a cladding layer.

[0008] Among them, the anchor is a bolt, and through holes are symmetrically provided on both sides of the gap. Through holes are provided at corresponding positions on the pad. The bolts are inserted into the through holes of the test plate and the pad to fix the test plate and the pad; a groove is provided at the center line of the upper surface of the pad to ensure forming.

[0009] Wherein, the width W of the test plate T 20~100mm, length L T 100~300mm, thickness D T 3 to 20 mm; the length of the gap L G The width of the gap is 0.5 to 0.6 times the length of the test plate. G The diameter of the through hole is 3 to 16 mm.

[0010] The laser cladding starts from the beginning of the gap and clads along the gap, and the cladding length is 0.5 to 1.5 times the length of the gap.

[0011] The method for evaluating the crack resistance of laser cladding materials using the above-mentioned device comprises the following steps:

[0012] (A) Cut a test plate, cut a slit at the center axis of one end of the test plate, and drill holes symmetrically on both sides of the slit with the slit as the axis of symmetry;

[0013] (B) Clean the surface of the test plate and fix the test plate to the backing plate with bolts;

[0014] (C) Laser cladding the metal powder along the gap to form a continuous cladding layer;

[0015] (D) Measure the crack length on the surface of the cladding layer and the total length of the cladding layer, and calculate the crack rate;

[0016] (E) The crack resistance of the cladding metal powder material is evaluated based on the crack rate δ.

[0017] Wherein, in step (C), during the laser cladding, the laser power is 1-3 kW, the scanning speed is 3-5 mm / s, and the feeding rate of the metal powder is 10-25 g / min.

[0018] Wherein, in step (C), a protective gas is used in the laser cladding process, and the protective gas is argon or helium; the flow rate of the protective gas is 10 to 20 L / min; and the protective gas is passed for 15 to 30 seconds before and after cladding.

[0019] In step (D), the crack rate (δ) is calculated using the following formula:

[0020] Crack rate (δ) = crack length (L C ) / total length of cladding layer (L S ).

[0021] The material of the test plate is one of nickel-based high-temperature alloy, aluminum alloy, titanium alloy, zirconium alloy, high entropy alloy, magnesium alloy or steel.

[0022] Wherein, in step (E), the crack sensitivity evaluation is: the lower the crack rate of the metal powder, the better the crack resistance. According to the size of the crack rate, the crack resistance of different metal powders is evaluated. The lower the crack rate, the better the laser cladding crack resistance of the metal powder under this condition. That is, the crack rates of the metal powders are compared and ranked. The lower the crack rate of the metal powder, the better the crack resistance. For example, the crack rates of the three metal powders A, B, and C are ranked as δ A >δ B >δ C When , it indicates that the crack resistance of the metal powder under the test conditions is C>B>A.

[0023] Principle of the invention: The present invention adopts a rectangular test plate with a gap, and connects the test plate to the pad by bolts to impose constraints. The bolt diameter and the number of bolts can be flexibly adjusted according to the size of the test plate to change the constraint. For example, when the test plate size is large, the constraint can be increased by increasing the bolt diameter and the number of bolts. Laser cladding tests with various process specifications can be carried out according to actual production needs. At the beginning of laser cladding, the constraint is large near the beginning of the gap to ensure the generation of cracks. As the cladding proceeds, the cracks continue to expand, but the constraint near the gap gradually decreases along the cladding direction. When the constraint decreases to a critical value, the crack stops expanding. Under certain cladding process parameters and powder types, the crack rate measured can be used to evaluate the laser cladding crack resistance of different metal powders under the same process parameters and the same metal powder under different process parameters.

[0024] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects: (1) The present invention only needs to use anchors, such as bolts, to fix the test plate and the backing plate. The method is simple to operate, the constraint degree can be flexibly adjusted, the crack rate calculation is simple, and the test results are reliable and effective. It can be used under various conditions, such as cladding nickel-based alloy powder on nickel-based alloy test plates, cladding nickel-based alloy powder on stainless steel test plates, etc., to evaluate the crack resistance of laser cladding materials; (2) The method of the present invention can evaluate the crack resistance of the same cladding material under different process parameters, which is of great significance to the optimization of the cladding layer composition, the development of high crack resistance cladding materials and the formulation of laser cladding processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the test plate of Example 1;

[0026] Figure 2 Schematic diagram of the pad of Example 1;

[0027] Figure 3 This is a physical picture of the crack results of the cladding layer in Example 1;

[0028] Figure 4 This is a graph showing the crack resistance test results of the same metal powder under different laser powers in Example 1;

[0029] Figure 5 This is a schematic diagram of the test plate of Example 2;

[0030] Figure 6 This is a graph showing the crack resistance test results of different metal powders in Example 2. DETAILED DESCRIPTION

[0031] The present invention is described in further detail below.

[0032] Example 1

[0033] The present invention provides a device for evaluating the crack resistance of laser cladding materials, comprising a test plate 1, such as Figure 1 As shown, a slit 3 is provided on the test plate 1. Anchors are used on both sides of the slit to fix the test plate 1 and the backing plate 2 with the slit 3 as the axis of symmetry. The surface of the slit 3 is covered with a cladding layer. The anchors in this embodiment are bolts. Through holes 4 are symmetrically provided on both sides of the slit. Through holes are provided at corresponding positions on the backing plate 2. Bolts are inserted into the through holes of the test plate 1 and the backing plate 2 to fix the test plate 1 and the backing plate 2. The structural diagram of the backing plate is shown in FIG. Figure 2 As shown, a groove (not shown) is provided at the center line of the upper surface of the pad to ensure the shaping.

[0034] In this example, Inconel718 nickel-based high-temperature alloy material is used as the cladding plate, and the cladding powder is Ni60A+35% WC. The crack resistance of the same cladding powder under different laser powers is evaluated:

[0035] (1) Test plate preparation: Inconel718 nickel-based high-temperature alloy test plates with a rectangular shape were cut by wire cutting. The length of the test plate is L T 120mm, width W T 21mm, thickness D T The length of the test plate is 3.8 mm, and the number is 9. Starting from the center axis of one end of the test plate, a length L is cut using a wire cutting machine. G 40mm, width W G The gap is 0.5mm, and holes are drilled on both sides of the gap. The diameter of the hole is Φ3mm, and the distance between the center of the hole on one side of the gap is L R The distance between the centers of the through holes on both sides of the gap is 105mm. R It is 13mm.

[0036] (2) Test plate cleaning: Before laser cladding, the test plate was cleaned with alcohol to remove oil and scale on the surface of the test plate.

[0037] (3) Application of restraint: Use bolts with a diameter of 3 mm to fix the test plate on the pad, where the length of the pad is L B 300mm, width W B 200mm, thickness D B The groove width on the pad is 5mm, the length is 300mm, and the depth is 8mm. Figure 2 As shown, Figure 2 This is a schematic diagram of the pad of Example 1.

[0038] (4) Cladding test: Laser cladding was performed. At the beginning of cladding, argon with a purity of 99.999% was used as the protective gas. The argon flow rate was 15 L / min, and argon was supplied for 15 seconds before and after cladding. A rectangular laser focus spot with a spot size of 5 mm × 5 mm was placed at the beginning of the gap. Under the action of laser heat, the alloy powder was melted and evenly coated on the gap surface. The rate of supplying metal powder was 15 g / min. Then, the laser was moved from the beginning to the end of the gap along the axis of the test plate at a scanning speed of 5 mm / s. After cladding 80 mm along the gap, the cladding was stopped, thereby forming a continuous cladding layer. During the cladding process, cracks on the cladding layer were generated and expanded. The expansion of the cracks stopped as the constraint degree decreased to a certain extent. The cladding was divided into three groups. The laser power of each group was 1.2 kW, 1.5 kW and 1.8 kW respectively. Each group of tests was repeated three times.

[0039] (5) Crack rate calculation and sensitivity evaluation: Measure the crack length L after cladding C ,like Figure 3 As shown, the average crack length of 3 specimens in each group is determined, and the measured crack length L C Divide by the total length of the cladding layer L SThe crack rate δ can be obtained. The crack rates δ obtained at 1.2kW, 1.5kW and 1.8kW laser powers are 0.15, 0.28 and 0.57 respectively. Figure 4 As shown, Figure 4 is the crack rate diagram of the same cladding powder under different laser powers, Figure 4 It can be seen that with the increase of laser power, the crack resistance of the cladding powder decreases. This is mainly because the increase in laser power leads to an increase in the amount of hard phase generated in the cladding layer, which makes it difficult to coordinate the strain. While improving the hardness and wear resistance of the cladding layer, it increases the cracking tendency of the cladding layer, resulting in increased crack sensitivity.

[0040] The crack rate rankings under the three laser powers are as follows: Figure 4 As shown in the figure, the lower the crack rate, the better the crack resistance of the cladding powder under this condition. Therefore, the crack resistance of the cladding powder materials under different laser powers is ranked from large to small as follows: laser power 1.2kW > laser power 1.5kW > laser power 1.8kW, which realizes the accurate and effective evaluation of the crack resistance of the same cladding powder material under different laser powers.

[0041] Example 2

[0042] In this example, Inconel718 nickel-based high-temperature alloy material was used as the cladding plate. The cladding powders were Ni60A, Ni60A+15%WC, Ni60A+25%WC, and Ni60A+35%WC. The crack resistance of different laser cladding powders was evaluated:

[0043] (1) Test plate preparation: Inconel718 nickel-based high-temperature alloy test plates with a rectangular shape were cut by wire cutting. The length of the test plate is L T 300mm, width W T 100mm, thickness D T The length is 20mm, the number is 12, and a length L is cut from the center axis of one end of the test plate using a wire cutting machine. G 100mm, width W G The gap is 1mm, and holes are drilled on both sides of the gap. The diameter of the hole is Φ16mm, and the distance between the center of the hole on one side of the gap is L R 250mm, L R1 The distance between the centers of the through holes on both sides of the gap is W R is 50mm, such as Figure 5 As shown, Figure 5 This is a schematic diagram of the test board of Example 2.

[0044] (2) Test plate cleaning: Before laser cladding, the test plate was cleaned with acetone solution to remove oil and scale on the surface of the test plate.

[0045] (3) Application of restraint: Use bolts with a diameter of 16 mm to fix the test plate on the pad, where the length of the pad is L B 400mm, width W B 300mm, thickness D B The groove width on the pad is 8mm, the length is 400mm and the depth is 12mm.

[0046] (4) Cladding test: Laser cladding was performed. At the beginning of cladding, argon with a purity of 99.999% was used as the protective gas. The argon flow rate was 20 L / min, and argon was supplied for 15 seconds before and after cladding. A rectangular laser focus spot with a laser power of 3 kW and a spot size of 5 mm × 5 mm was placed at the beginning of the gap. Under the action of laser heat, the alloy powder was melted and evenly coated on the gap surface. The rate of supplying metal powder was 25 g / min. Then, the laser was moved from the beginning to the end of the gap along the central axis of the test plate at a scanning speed of 3 mm / s. After cladding 200 mm along the gap, the cladding was stopped, thereby forming a continuous cladding layer. During the cladding process, cracks on the cladding layer were generated and expanded. The expansion of the cracks stopped as the constraint degree decreased to a certain level. The cladding was divided into four groups. The cladding powder types of each group were Ni60A, Ni60A+15%WC, Ni60A+25%WC and Ni60A+35%WC. Each group was tested three times.

[0047] (5) Crack rate calculation and sensitivity evaluation: Measure the crack length L after cladding C , the average crack length of 3 specimens in each group is determined, and the measured crack length L C Divide by the total length of the cladding layer L S The crack rate δ can be obtained. When the cladding powder types are Ni60A, Ni60A+15%WC, Ni60A+25%WC and Ni60A+35%WC, the crack rates δ are 0.13, 0.29, 0.60 and 0.77 respectively. Figure 6 As shown, Figure 6 is the crack rate diagram under different cladding powder types, Figure 6 It can be seen that with the increase of WC content, the crack resistance of the cladding powder decreases. This is mainly because the increase in WC content leads to an increase in the amount of hard phase generated in the cladding layer, which makes it difficult to coordinate the strain. While improving the hardness and wear resistance of the cladding layer, it increases the cracking tendency of the cladding layer, resulting in a decrease in the crack resistance of the cladding powder.

[0048] The crack rate ranking of the four cladding powders is as follows: Figure 6As shown in the figure, the lower the crack rate, the higher the crack resistance of the cladding powder under this condition. Therefore, the crack resistance of different cladding powder materials obtained in the experiment is Ni60A>Ni60A+15%WC>Ni60A+25%WC>Ni60A+35%WC, which realizes the accurate and effective evaluation of the crack resistance of different cladding powder materials.

Claims

1. A device for evaluating crack resistance of laser cladding materials, characterized in that: The invention comprises a test plate (1), wherein a slit (3) is provided on the test plate (1), and the test plate (1) and the backing plate (2) are fixed on both sides of the slit (3) by anchoring pieces with the slit (3) as a symmetric axis; the surface of the slit (3) is covered with a cladding layer; The anchoring piece is a bolt, through holes (4) are symmetrically provided on both sides of the gap (3), and through holes are provided at corresponding positions on the pad (2). The bolts are inserted into the through holes of the test plate (1) and the pad (2) to fix the test plate (1) and the pad (2); the test plate and the pad are connected by the bolts to impose constraints, and the bolt diameter and the number of bolts can be flexibly adjusted according to the size of the test plate to change the constraint degree.

2. The device for evaluating crack resistance of laser cladding materials according to claim 1, characterized in that: The width W of the test plate (1) T 20~100mm, length L T 100~300mm, thickness D T 3~20mm.

3. The device for evaluating crack resistance of laser cladding materials according to claim 1, characterized in that: The length L of the gap (3) G The width W of the gap (3) is 0.5 to 0.6 times the length of the test plate (1). G 0.5~1mm.

4. The device for evaluating crack resistance of laser cladding materials according to claim 1, characterized in that: The cladding layer starts along the starting end of the gap (3), and the length of the cladding layer is 0.5 to 1.5 times the length of the gap (3).

5. The device for evaluating crack resistance of laser cladding materials according to claim 1, characterized in that: The diameter of the through hole is 3-16 mm.

6. The device for evaluating crack resistance of laser cladding materials according to claim 1, characterized in that: A groove is provided at the center line of the upper surface of the pad (2) to ensure forming.

7. A method for evaluating the crack resistance of laser cladding materials using the device according to claim 1, characterized in that: The following steps are involved: (A) Cut a test plate (1), cut a slit (3) at the center axis of one end of the test plate (1), and drill holes symmetrically on both sides of the slit (3) with the slit (3) as the symmetry axis; (B) Clean the surface of the test plate (1) and fix the test plate (1) on the backing plate (2) with bolts; (C) laser cladding the metal powder along the gap (3) to form a continuous cladding layer; (D) Measure the crack length on the surface of the cladding layer and the total length of the cladding layer, and calculate the crack rate; (E) Evaluate the crack resistance of the cladding metal powder material based on the crack rate δ.

8. The method for evaluating crack resistance of laser cladding materials according to claim 7, characterized in that: In step (C), during the laser cladding, the laser power is 1-3 kW, the scanning speed is 3-5 mm / s, and the feeding rate of the metal powder is 10-25 g / min.

9. The method for evaluating crack resistance of laser cladding materials according to claim 7, characterized in that: In step (C), a protective gas is used in the laser cladding process, and the protective gas is argon or helium; the flow rate of the protective gas is 10-20 L / min, and the protective gas is passed for 15-30 seconds before and after the cladding.

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