Research On Laser Cladding AlCoCrFeNiTi High-Entropy Alloy On H13 Steel And Their High-temperature Wear Mechanism

As a widely used hot work die steel,H13 steel possesses a series of excellent properties,such as high hardenability,toughness,wear resistance and good fatigue performance.However,under severe conditions,H13 steel tends to fail early due to thermal wear.Compared with traditional alloys,high-entropy alloys possess excellent properties such as high strength,hardness,corrosion resistance,and high-temperature softening resistance due to their sluggish diffusion effect and cocktail effect.Therefore,the high-temperature wear resistance of H13 steel can be improved by surface modification with high-entropy alloy,which extends the service life of hot work dies.In this research,high-entropy alloy coats were laser cladded on H13 steel.The microstructure,composition and performance of coats were analyzed.The hightemperature tribological experiments on H13 steel and high-entropy alloy coats was carried out at the temperature of 400?C and 600?C,respectively.To study the wear behavior and wear resistance of H13 steel and high-entropy alloy coats,the morphology,composition,phase and hardness of the worn surface and cross section of H13 steel and high-entropy alloy coats were analyzed by SEM,EDS,XRD and Vickers hardness tester.The wear mechanism and anti-wear mechanism of high-entropy alloy coats were discussed.AlCoCrFeNiTi high-entropy alloy coats were laser cladded on H13 steel according to a series of parameters.These laser cladding coats were complete,dense and metallurgically bonded to the substrate.These coats consisted of BCC single phase.In the top area of these coats,grains were very fine.In the area adjacent to the heat-affected zone,there was a combination of planar crystals and columnar crystals.For the inner area,the grains in some coats were equiaxed,while those in other coats were dendritic.The results of high-temperature tribological experiments show that the mass of H13 steel decreased obviously after wear.Especially,when the experimental temperature was 600?C and the load was high,the mass of H13 steel decreased dramatically after wear.However,the mass loss of high-entropy coats was significantly reduced.When the experimental temperature was 600?C,the mass change of highentropy coats could be positive,which means the wear resistance of high-entropy coats is much higher than that of H13 steel.Furthermore,the friction coefficient trends of H13 steel and high-entropy alloy coats were found to be very similar: as the load increased,the friction coefficient at the experimental temperature of 400?C decreased gradually,but the friction coefficient at the experimental temperature of 600?C increased gradually.Based on the microscopic analysis,the wear mechanism of H13 steel and highentropy alloy coats can be summarized.When the experimental temperature was 400?C,as the load increased,the wear mechanism of H13 steel transitioned from the combination of slightly oxidative wear and abrasive wear to a single mode of slightly oxidative wear,while that of high-entropy alloy coats was always the combination of slightly oxidative wear and abrasive wear.When the experimental temperature was600?C,as the load increased,the wear mechanism of H13 steel transitioned from the single mode of slightly oxidative wear to a combination of oxidative and fatigue wear,while that of high-entropy alloy coats was always slightly oxidative wear.