Study On Microstructure And Properties Of The High Alloy Content High Speed Steel Coating Produced By Laser Cladding

The M2?W6Mo5Cr4V2?high-speed steel coating was prepared by laser cladding.It was found that the coating had fine structure after solidification,but the laser non-equilibrium rapid solidification enhanced the solid solubility of strong carbide forming elements such as W and Mo in the matrix.As a result,the precipitation of hard carbides in the coating is greatly reduced,and the carbides are distributed as network.Therefore,this paper proposes the design idea of laser rapid solidification high alloy content high speed steel composition,which is mainly divided into the following two categories:The first type is to add high-content strong carbide forming elements like W,Mo,V to the typical M2 high-speed steel to obtain more hard precipitated carbide phase,thus three alloy compositions for High Mo-Co,high Mo-Co-V,high W-Mo-V are proposed;The second type is Fe₆₈?WMoCrVCoNiCuAl?₃₂2 coating combined with multi-component medium entropy steel composition,and the effects of C,W,Al,Cu are studied.The experimental results show that the microstructure of high-alloy content HSS coatings?high Mo-Co,high Mo-Co-V,high W-Mo-V?is acicular martensite,a small amount of retained austenite and M₂C type carbides distributed among grain boundary.After tripple tempered at530°C,the retained austenite have almost eliminated,and the secondary carbides precipitated on the grain boundary and tempered martensite matrix;Compared with the M2 coating with aged hardness of 813 HV_0.5,the increase of strong carbide forming elements?W,Mo?is beneficial to obtain more hard carbides in the coating.The maximum hardness reached 872HV_0.5,but the carbide network distribution is more obvious,which is not conducive to the cracking performance of coating,besides,the wear performance under 500°C is close to M2high speed steel.All the Medium-entropy coatings obtained typical martensitic matrix,M₂C carbides and a small amount of retained austenite phase after solidification.Moreover,the carbide distribution is relatively dispersed with finer size,and reduced mesh distribution,and the aging hardness is between 810 HV_0.5 and 870 HV_0.5.TEM observations show that compared with the M2high-speed steel coating,the significant secondary hardening effect of the medium-entropy high-speed steel coating comes from the nano-scale M₂C carbide precipitated on the martensite matrix.The 500°C hot wear test shows that the medium entropy high-speed steel has a lower friction coefficient than the M2 high-speed steel coating,and the weight lossing is reduced over50%.It can be seen that this project combines the technical characteristics of laser rapid solidification,proposes the two design ideas of high-alloy content laser cladding high-speed steel composition,Compare to the High-speed steel composition design relative to the high-strength carbide alloy content that causes the coating toughness to decrease,the Medium-entropy High-speed steel owns a much better hot wear resistance under the temperature of 500°C,science it contains more oxidation-resistant components,significant nano-scale age hardening effect,Higher toughness and silimar hardness compare to M2 high speed steel coating.