Enhanced wear and corrosion resistances of AlCoCrFeNi high-entropy alloy coatings via high-speed laser cladding

Abstract

In this study, an AlCoCrFeNi high-entropy alloy (HEA) coating was prepared on the surface of AISI 1045 steel by high-speed laser cladding (HLC). The microstructure, phase composition, element distribution, microhardness, wear, and corrosion resistance of the coatings were analyzed, respectively. It was found that a metallurgical bond was formed, the mail microstructure were the fine columnar and equiaxed dendrites, and the phase composition of the coating was a single-phase bulk cubic-centered structure (BCC/B2). Moreover, the elements of the HLC coating were evenly distributed without obvious segregation. Compared to conventional laser cladding (CLC), the efficiencies of cladding and processing quality were higher. The scanning speed of CLC was 10 mm/s with some pores and overburning on the surface of the coating. However, the scanning speed of HLC increased by 30 times to 300 mm/s, and the surface roughness of the HLC coating was 39.83% lower. The dilution ratio of the HLC coatings was 4.6%, which was 3 times lower than that of 13.4% by CLC. It also leads to a significant decrease in the grain size, element transition zone, and heat affected zone. As a result, the hardness of the coating increased by 100 HV, the friction coefficient decreased by 0.15, the wear weight loss was reduced by 9.85%, the self-corrosion potential increased by 84 mV, and the self-corrosion current density was one order of magnitude lower. Therefore, the potential application of HLC is suggested to effectively improve the wear and corrosion resistances of HEA coatings. Coatings were prepared by both conventional laser cladding (CLC) and high-speed laser cladding (HLC). The intersection of the laser beam and the powder stream in CLC was on the surface of the substrate, but in HLC it was slightly elevated above the surface of the substrate. Since 65% of the laser energy was used to melt the powder, and only a small amount of laser energy was used to melt the substrate, the area of the coating pools, the heat affected zone, and the dilution rate were reduced. The HLC coating was denser and finer, with consistent dendritic development in the same direction, and its roughness was only 60.17% of that of the CLC coating. Under the same test circumstances, the surface microhardness of the HLC coating rose by 100 HV, while the coefficient of friction and weight loss decreased. Furthermore, abrasive wear characteristics were more obvious. The grain boundaries of the HLC coating were enriched with Ni and Cr, and the area of the passivation film was increased. The passivation tendency of the coating became more evident as the arithmetic mean equilibrium potential increased. • HLC had a scanning speed of 300 mm/s, which was about 30 times faster than CLC. • The surface roughness of the HLC coating was 39.83% lower. • The HLC coating was denser and was also composed of a single-phase BCC/B2 structure. • The microhardness, wear and corrosion resistances of the HLC coating were enhanced. • AlCoCrFeNi HEA coating was mainly strengthened by fine grain strengthening.