Effect of Fast Axial Flow CO₂ Laser Processing Parameters on Graphene/Al_xCoCrNiTi High Entropy Alloy

Abstract

The energy distribution characteristics of fast axial flow CO₂ lasers demonstrate that they are often used for cutting and welding metal materials, and it is generally believed that they are not suitable for material heat treatment. In order to expand the application range of these lasers, we prepare graphene (Gr) reinforced high entropy alloy (HEA) coatings, employing this type of laser under loworder mode conditions by adjusting processing parameters and cladding powder composition through orthogonal experiments. Then we study the effect of laser processing parameters on Gr/Al_xCoCrNiTi composite coatings. The research results indicate that the optimum process parameters are as follows: the laser power P = 3200 W, the scanning speed V = 14 mm/s, the cladding powder thickness d = 1.2 mm, and the spot diameter D = 4.0 mm. We find that, under the optimum process parameters, the Gr/Al_xCoCrNiTi laser cladding coatings exhibit typical dendrites and equiaxed grains. The microstructure refines with increase in the Al content. The Gr/AlxCoCrNiTi laser cladding coating mainly consists of the face centered cubic (FCC), body centered cubic (BCC), and M₂₃C₆. Increase in the Al content promotes the formation of the BCC structure. The microhardness of Gr/Al_xCoCrNiTi composite coatings range from 550 to 725 HV. The hardness is related to the solid solution strengthening caused by Gr and Al. With increase in the Al content, the microhardness of the coating shows a trend to increase, the wear resistance first increases and then decreases. The wear resistance is related to the BCC content and cracks in the coating. Orthogonal experiments and coating performance indicate that, by adjusting laser processing parameters and alloy composition, it is possible for fast axial flow CO₂ lasers to prepare Gr/Al_xCoCrNiTi composite coatings under low-order mode conditions, which can expand the applicability of these lasers.