Laser composite strengthening method and application for high surface hardness uniformity

Abstract

The present invention discloses a laser composite strengthening method with high surface hardness uniformity and its application. The laser composite strengthening method comprises: performing laser remelting along multiple remelting paths on the surface of a metal component to form a remelting layer, and there is overlap between adjacent remelting paths, and adjacent remelting spots in any remelting path overlap; performing multiple rounds of laser quenching along multiple quenching paths on the surface of the remelting layer to form a quenching layer, and in any round, there is overlap between adjacent quenching paths, and adjacent quenching spots in any quenching path are separated from each other, and for the quenching path, the spot positions between multiple rounds complement each other to form overlaps. The laser composite strengthening method provided by the present invention compensates for the thermal interference between the spots by performing laser quenching with a smaller spot size and smaller heat input on the surface of the remelting layer, and forming quenching paths with partial overlap through multiple rounds of complementarity, thereby forming a surface hardened layer with uniform hardness on the surface of the component.

Description

Technical Field

[0001] The present invention relates to the field of surface engineering technology, and in particular to a laser composite strengthening method with high surface hardness uniformity and its application, which is mainly used for preparing a wear-resistant and corrosion-resistant surface strengthening layer of a key component. Background Art

[0002] Laser remelting can obtain a surface layer with ultra-fine structure, the same composition as the matrix, and complete metallurgical bonding on the surface of the steel matrix through rapid cooling, which significantly improves the surface hardness and wear and corrosion resistance of steel components. It is considered to be a very promising surface strengthening method. However, the microstructure of the laser remelting molten pool after solidification is not uniform, and there is a high overlap rate between adjacent spots and passes during laser cladding or remelting. The spot of the latter pass has a thermal effect on the previous remelted solidified structure, resulting in uneven microstructure and performance of the remelted surface. In actual use, this unevenness will cause local wear or pitting, reducing the expected service life. This quality problem limits the application scope of laser remelting strengthening. Therefore, in order to realize the large-scale application of laser remelting, a laser surface strengthening method that can obtain more uniform surface hardness is needed. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a laser composite strengthening method and application with high surface hardness uniformity.

[0004] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0005] In a first aspect, the present invention provides a laser composite strengthening method for achieving high surface hardness uniformity, comprising:

[0006] Laser remelting is performed on the surface of the metal component along a plurality of remelting paths using a first spot diameter and a first heat input to form a remelting layer, wherein adjacent remelting paths overlap and adjacent remelting spots in any remelting path overlap;

[0007] performing multiple rounds of laser quenching on the surface of the remelted layer along multiple quenching lanes using a second spot diameter and a second heat input to form a quenched layer, wherein adjacent quenching lanes are overlapped in any round, adjacent quenching spots in any quenching lane are separated from each other, and for the quenching lane, the positions of the spots in multiple rounds complement each other to form an overlap;

[0008] The first light spot diameter is larger than the second light spot diameter, and the first heat input is higher than the second heat input.

[0009] In a second aspect, the present invention further provides a surface-strengthened component manufactured by the above-mentioned laser strengthening composite method, which comprises a component substrate, a remelting layer, and a quenching layer stacked in sequence;

[0010] The remelting layer includes remelting spots arranged along multiple remelting lanes, and the quenching layer includes quenching spots arranged along multiple quenching lanes. There is overlap between adjacent remelting lanes, and adjacent remelting spots in any remelting lane overlap. There is overlap between adjacent quenching lanes. The quenching spots in any quenching lane are divided into multiple rounds, and the quenching spots in any round are separated from each other, and the positions of the quenching spots in multiple rounds complement each other to form an overlap.

[0011] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention include at least:

[0012] The laser composite strengthening method provided by the present invention performs laser quenching with a smaller spot size and smaller heat input on the surface of the remelting layer, and forms partially overlapping quenching paths through multiple rounds of complementary quenching, thereby compensating for the thermal interference between the spots, thereby forming a surface hardened layer with uniform hardness on the surface of the component, and the surface flatness of the formed strengthening layer is high.

[0013] The above description is only an overview of the technical solution of the present invention. In order to enable those skilled in the art to more clearly understand the technical means of this application and implement them according to the contents of the specification, the following is an explanation of the preferred embodiments of the present invention with detailed drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the relationship between the spot path and the spot position of the laser composite strengthening method provided by a typical embodiment of the present invention;

[0015] Figure 2 Schematic diagram of the distribution of surface hardness test points provided by some typical implementation cases and comparative cases of the present invention;

[0016] Figure 3 This is a hardness distribution test diagram of the surface strengthening layer provided by a typical comparative case of the present invention;

[0017] Figure 4 This is a hardness distribution test diagram of the surface strengthening layer provided by a typical embodiment of the present invention;

[0018] Figure 5 This is a hardness distribution test diagram of the surface strengthening layer provided by another typical embodiment of the present invention;

[0019] Figure 6 This is a hardness distribution test diagram of the surface strengthening layer provided by another typical embodiment of the present invention. DETAILED DESCRIPTION

[0020] In view of the shortcomings of the prior art, the inventors of this case, after long-term research and extensive practice, have proposed the technical solution of the present invention. The following will further explain this technical solution, its implementation process and principles.

[0021] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0022] Moreover, relational terms such as “first” and “second” are merely used to distinguish one component or method step from another with the same name, but do not necessarily require or imply any actual relationship or order between these components or method steps.

[0023] The embodiment of the present invention provides a laser composite strengthening method for achieving high surface hardness uniformity, which includes the following steps:

[0024] Laser remelting is performed on the surface of the metal component along a plurality of remelting paths using a first spot diameter and a first heat input to form a remelting layer, wherein adjacent remelting paths overlap and adjacent remelting spots in any remelting path overlap;

[0025] performing multiple rounds of laser quenching along multiple quenching lanes on the surface of the remelted layer using a second spot diameter and a second heat input to form a quenched layer, wherein adjacent quenching lanes in any round are overlapped, adjacent quenching spots in any quenching lane are separated from each other (do not overlap), and for the quenching lane, the positions of the spots in multiple rounds complement each other to form an overlap;

[0026] The first light spot diameter is larger than the second light spot diameter, and the first heat input is higher than the second heat input.

[0027] The main technical means of the above technical solution is to prepare a remelting layer on the surface of the steel component to be strengthened under the conditions of large spot and high heat input, and then use a small spot and lower heat input for quenching to obtain a surface hardened layer with high hardness and uniformity. The purpose is to provide a laser composite strengthening technology that can achieve high and uniform hardness of the surface remelting layer, replacing the traditional laser cladding or remelting technology for the surface strengthening of steel wear-resistant and corrosion-resistant components.

[0028] It is worth noting that in the present invention, the diameter of the quenching spot is smaller than the diameter of the remelting spot, and the overlapping arrangement is achieved by a single-round discrete and multi-round complementary method. This is because there is a high overlap rate between adjacent spots and passes during laser cladding or remelting, and the spot of the later pass has a thermal impact on the previous remelted solidified structure, which leads to unevenness. The laser quenching in the present invention compensates for the above-mentioned unevenness and strengthens it, so the quenching spot needs to be smaller in size; in addition, since two quenching spots adjacent in time will cause heat superposition and affect each other, it is not appropriate to use a single-round overlapping method to directly complete laser quenching, but requires a multi-round overlapping method to complete it.

[0029] For detailed spot distribution, see Figure 1 As shown, in some embodiments, the quenching track is arranged in parallel with the remelting track, and the center line of the quenching track runs along the overlapping seam of the two adjacent remelting tracks; the overlapping seam refers to the common tangent line of the edges of multiple remelting spots in the adjacent subsequent remelting track, and the common tangent line is located on the side close to the previous remelting track.

[0030] In some embodiments, N represents the number of laser quenching rounds, L represents the center distance between adjacent quenching spots in any quenching lane in any round, and P represents the center offset distance between quenching spots in adjacent rounds in any quenching lane. Then:

[0031] P = L / N;

[0032] Wherein, L>L0, L0 refers to the second light spot diameter.

[0033] In some embodiments, the number of rounds of laser quenching is 2-3 rounds.

[0034] In some embodiments, in any one of the quenching lanes, the overall overlap rate of the quenching spots of all rounds is 40-60%.

[0035] In some embodiments, during the laser remelting, the overlap rate of adjacent remelting tracks is 60-70%, and the overlap rate of light spots in any remelting track is 60-80%.

[0036] In some embodiments, during the laser quenching, the overlap rate between adjacent quenching lanes is 20-30%.

[0037] In some embodiments, the first light spot has a diameter of 0.5-2.0 mm.

[0038] In some embodiments, the second spot diameter is 40-60% of the first spot diameter.

[0039] As for other condition parameters, such as heat input controlled by current, pulse width and frequency, adaptive adjustments can be made for different materials, different cladding thicknesses, etc., and you can refer to many existing technologies or experiment with the process window yourself; not only that, the irradiation frequency of remelting and quenching can also be adaptively adjusted to match the scanning speed, the main purpose of which is to control the overlap rate.

[0040] In some embodiments, the last spot of the laser remelting and the laser irradiation are completely outside the preset strengthening area of ​​the metal component to avoid a complete molten pool remaining.

[0041] A second aspect of the embodiments of the present invention further provides a surface-reinforced component manufactured by the laser strengthening composite method according to any of the above embodiments, comprising a component substrate, a remelting layer, and a quenching layer stacked in sequence;

[0042] The remelting layer includes remelting spots arranged along multiple remelting lanes, and the quenching layer includes quenching spots arranged along multiple quenching lanes. There is overlap between adjacent remelting lanes, and adjacent remelting spots in any remelting lane overlap. There is overlap between adjacent quenching lanes. The quenching spots in any quenching lane are divided into multiple rounds, and the quenching spots in any round are separated from each other, and the positions of the quenching spots in multiple rounds complement each other to form an overlap.

[0043] As some typical examples of the above technical solutions, the present invention provides a laser composite strengthening method that combines laser surface large-spot high-heat input remelting with small-spot low-heat input quenching, which can be used for surface wear and corrosion protection of metal components such as large-size hot working molds, especially steel components. The main steps are as follows: first, the surface of the steel component is cleaned to remove surface stains and oxide layers, and then the surface is remelted under conditions of large spot and high heat input. The laser equipment, current, scanning speed, pulse frequency, pulse width, spot size, etc. can be flexibly selected, with an overlap rate of 60-70% between passes and a spot overlap rate of 60-80%. Then, a small spot and low heat input are used to quench the tangent area of ​​the remelted spot. The quenching spot diameter is 40-60% of the remelted spot. This is done in 2-3 rounds. The spots in any pass of each round are discontinuous and spaced apart to ensure the quenching effect. The spots in the next round or multiple rounds fill the gaps and form a complementary effect. Finally, the spot overlap rate of the overlapping passes is 40-60%, resulting in a surface hardened layer with uniform hardness. The advantages of the above technical solution are that it can produce a remelted quenched strengthening layer with high and uniform microstructure, surface hardness, corrosion resistance, and hardened layer thickness, with a smooth surface and low energy consumption.

[0044] Exemplarily, the main component of the components used in the embodiments of the present invention can be low alloy steel or stainless steel, but it is not limited to this. Metal materials with similar properties that can be subjected to surface laser quenching and strengthening treatment can utilize the technical solution provided by the present invention, such as nickel alloys, titanium alloys, aluminum alloys, high alloy steels, etc. Of course, the spot size and overlap arrangement of different materials should meet the above requirements, but some other condition parameters such as laser power need to be adaptively adjusted.

[0045] The technical solution of the present invention is further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0046] Comparative Example 1

[0047] The surface of the 10mm thick H13 hot working die steel plate was mechanically polished to remove surface stains and oxide layer, and then rinsed with water and alcohol in turn and then blown dry;

[0048] The laser remelting current is 50A, the scanning rate is 108mm / min, the spot diameter is 0.6mm, the frequency is 10Hz, and the pulse width is 6ms to achieve a 70% overlap rate; the overlap rate between passes is 60%; the remelting path is as follows Figure 1 As shown, the final light spot ends outside the workpiece.

[0049] The surface hardness of the remelting spot was measured using a micro Vickers hardness tester with a load of 50 g and a holding time of 10 s. The microhardness indentation position was measured along the diameter of the remelting spot at intervals of 0.03 mm. Figure 2 As shown, there are 100 points in total, and the hardness distribution is obtained as Figure 3 In the figure, 1 to 10 refer to a row of test points from top to bottom, and the vertical axis is the hardness of each row from left to right.

[0050] Example 1

[0051] This embodiment adds a laser quenching process based on the comparative example 1, which is as follows:

[0052] The surface of the 10mm thick H13 hot working die steel plate was mechanically polished to remove surface stains and oxide layer, and then rinsed with water and alcohol in turn and then blown dry;

[0053] The laser remelting current is 50A, the scanning rate is 108mm / min, the spot diameter is 0.6mm, the frequency is 10Hz, and the pulse width is 6ms to achieve a 70% overlap rate; the overlap rate between passes is 60%; the remelting path is as follows Figure 1 As shown, the final light spot ends outside the workpiece.

[0054] The laser quenching current was 15A, the scanning rate was 190mm / min, the spot diameter was 0.3mm, the frequency was 10Hz, and the pulse width was 8ms, so that the quenching spots did not overlap. The overlap rate between passes was 24%. Two rounds of laser quenching were performed, and the quenching paths of the two passes were consistent, both following the joints of the remelted spots. However, the spot offset along the quenching path was half the quenching spot spacing.

[0055] The surface hardness of the remelting spot was measured using a micro Vickers hardness tester with a load of 50 g and a holding time of 10 s. The hardness distribution was obtained along the diameter of the remelting spot at intervals of 0.03 mm. Figure 4 shown.

[0056] Comparative Example 2

[0057] This comparative example is substantially the same as Example 1, with the main difference being:

[0058] When laser quenching is performed, it is not divided into multiple rounds, but all quenching spots are irradiated in one round, and the irradiation frequency remains unchanged.

[0059] The result is that the surface hardness is low, and the average hardness is reduced by 10-15% compared with Example 1. The reason is that the latter laser pulse is emitted before the high temperature caused by the previous pulse has dropped, which delays the temperature drop and thus reduces the quenching effect.

[0060] Comparative Example 3

[0061] This comparative example is substantially the same as Example 1, with the main difference being:

[0062] During laser quenching, the quenching path does not run along the joints of the remelted spots, but runs along the center of the remelted spots.

[0063] The consequence is that the hardness of the overlap area is low, and the gap with the center area increases. The reason is that the hardness of the joint area itself is low, and without further quenching, its hardness is even greater than that of the center area that has undergone secondary quenching.

[0064] This shows that making the quenching path run along the joints of the remelted spots is the key factor in compensating for the hardness non-uniformity by utilizing the arrangement of the quenching spots.

[0065] Example 2

[0066] The surface of the 6mm thick H13 hot working die steel plate was mechanically polished to remove surface stains and oxide layer, and then rinsed with water and alcohol in turn and then blown dry;

[0067] The laser remelting current is 45A, the scanning rate is 108mm / min, the spot diameter is 0.6mm, the frequency is 10Hz, and the pulse width is 8ms to achieve a 70% overlap rate; the overlap rate between passes is 60%; the remelting path is as follows Figure 1 As shown, the final light spot ends outside the workpiece.

[0068] The laser quenching current was 12A, the scanning rate was 190mm / min, the spot diameter was 0.3mm, the frequency was 10Hz, and the pulse width was 7ms, so that the quenching spots did not overlap; the overlap rate between passes was 24%;

[0069] Two rounds of quenching were performed, with the starting positions of the two rounds offset by half the spacing of the quenching spots;

[0070] The surface hardness of the remelting spot was measured using a micro Vickers hardness tester with a load of 50 g and a holding time of 10 s. The hardness distribution was obtained along the diameter of the remelting spot at intervals of 0.03 mm. Figure 5 shown.

[0071] Example 3

[0072] The surface of 8mm thick H13 hot working die steel plate was mechanically polished to remove surface stains and oxide layer, and then rinsed with water and alcohol in turn and then blown dry;

[0073] The laser remelting current is 40A, the scanning rate is 108mm / min, the spot diameter is 0.6mm, the frequency is 10Hz, and the pulse width is 8ms to achieve a 70% overlap rate; the overlap rate between passes is 60%; the remelting path is as follows Figure 1 As shown, the final light spot ends outside the workpiece.

[0074] The laser quenching current was 10A, the scanning rate was 190mm / min, the spot diameter was 0.3mm, the frequency was 10Hz, and the pulse width was 10ms, so that the quenching spots did not overlap; the overlap rate between passes was 24%;

[0075] Two rounds of quenching were performed, with the starting positions of the two rounds offset by half the spacing of the quenching spots;

[0076] The surface hardness of the remelting spot was measured using a micro Vickers hardness tester with a load of 50 g and a holding time of 10 s. The hardness distribution was obtained along the diameter of the remelting spot at intervals of 0.03 mm. Figure 6 shown.

[0077] Example 4

[0078] This embodiment is substantially the same as embodiment 3, with the main difference being that during laser quenching, the scanning rate is 190 mm / min, the frequency used is 15 Hz, the spot diameter is 0.2 mm, and the spot spacing is 0.21 mm; three rounds of quenching are performed, and the starting position offset of each round of quenching is 1 / 3 of the spot spacing.

[0079] The obtained surface composite strengthening layer still has a relatively high hardness value and hardness uniformity.

[0080] Example 5

[0081] This embodiment is substantially the same as embodiment 3, with the main difference being that the base material is replaced with stainless steel, model TC4 titanium alloy.

[0082] When other conditions remain unchanged, the obtained surface composite strengthening layer still has a high hardness value and hardness uniformity.

[0083] Example 6

[0084] This embodiment is substantially the same as embodiment 3, with the main difference being that the substrate is replaced with 3003 aluminum alloy.

[0085] When other conditions remain unchanged, the obtained surface composite strengthening layer still has a high hardness value and hardness uniformity.

[0086] Based on the above embodiments and comparative examples, it can be clearly seen that the laser composite strengthening method provided in the embodiments of the present invention compensates for the thermal interference between the light spots by performing laser quenching with a smaller spot size and smaller heat input on the surface of the remelting layer, and forms a quenching path with partial overlap through multiple rounds of complementarity, thereby forming a surface hardened layer with uniform hardness on the surface of the component, and the surface flatness of the formed strengthening layer is high, and the energy consumption of the surface strengthening process is low.

[0087] It should be understood that the above embodiments are merely illustrative of the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent variations or modifications made in accordance with the spirit and substance of the present invention are intended to be encompassed within the scope of protection of the present invention.

Claims

1. A laser composite strengthening method for achieving high surface hardness uniformity, characterized in that: include: Laser remelting is performed on the surface of the metal component along a plurality of remelting paths using a first spot diameter and a first heat input to form a remelting layer, wherein adjacent remelting paths overlap and adjacent remelting spots in any remelting path overlap; performing multiple rounds of laser quenching on the surface of the remelted layer along multiple quenching lanes using a second spot diameter and a second heat input to form a quenched layer, wherein adjacent quenching lanes are overlapped in any round, adjacent quenching spots in any quenching lane are separated from each other, and for the quenching lane, the positions of the spots in multiple rounds complement each other to form an overlap; The diameter of the first light spot is larger than the diameter of the second light spot, and the first heat input is higher than the second heat input. The quenching track is arranged in parallel with the remelting track, and the center line of the quenching track runs along the overlapping seam of two adjacent remelting tracks. The overlapping seam refers to the common tangent line of the edges of multiple remelting spots in the adjacent subsequent remelting track, and the common tangent line is located on the side close to the previous remelting track. N represents the number of laser quenching rounds, L represents the center distance between adjacent quenching spots in any quenching track in any round, and P represents the center offset distance of quenching spots in adjacent rounds in any quenching track. Then: P = L / N; Wherein, L>L0, L0 refers to the second light spot diameter.

2. The laser strengthening composite method according to claim 1, characterized in that: The number of rounds of laser quenching is 2-3 rounds.

3. The laser strengthening composite method according to claim 1, characterized in that: In any of the quenching lanes, the overall overlap rate of the quenching spots of all rounds is 40-60%.

4. The laser strengthening composite method according to claim 1, characterized in that: During the laser remelting, the overlap rate of adjacent remelting paths is 60-70%, and the overlap rate of light spots in any remelting path is 60-80%.

5. The laser strengthening composite method according to claim 4, characterized in that: During the laser quenching, the overlap rate between adjacent quenching lanes is 20-30%.

6. The laser strengthening composite method according to claim 1, characterized in that: The diameter of the first light spot is 0.5-2.0 mm; And / or, the diameter of the second light spot is 40-60% of the diameter of the first light spot.

7. The laser strengthening composite method according to claim 1, characterized in that: The last light spot of the laser remelting and the laser irradiation are completely outside the preset strengthening area of ​​the metal component.

8. The surface-reinforced component obtained by the laser strengthening composite method according to any one of claims 1 to 7, characterized in that: It includes a component base, a remelting layer and a quenching layer stacked in sequence; The remelting layer includes remelting spots arranged along multiple remelting lanes, and the quenching layer includes quenching spots arranged along multiple quenching lanes. There is overlap between adjacent remelting lanes, and adjacent remelting spots in any remelting lane overlap. There is overlap between adjacent quenching lanes. The quenching spots in any quenching lane are divided into multiple rounds, and the quenching spots in any round are separated from each other, and the positions of the quenching spots in multiple rounds complement each other to form an overlap.

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