Understanding Stellite-6 coating prepared by laser cladding: Convection and columnar-to-equiaxed transition

Abstract

In the Stellite-6 coating prepared by laser cladding technology, temperature gradient and solidification rate play a critical role in grain growth. The columnar-to-equiaxed transformation behavior significantly affects the properties of the coating. In this paper, a finite element model including the changes of convection and temperature field in the melt pool was established, and the effects of laser power on the geometric characteristics and columnar-to-equiaxed transformation behavior of the coating were analyzed. The results show that the laser power significantly improve the convection intensity of metal liquid, which increased the width, depth and dilution ratio of the coating. In the solidification process of melt pool, convection gradually changed from diffusion around the coating to reflux to the top of the coating. Lower temperature gradient and higher solidification rate were conducive to the growth of equiaxed crystals. The microhardness of equiaxed crystal region was higher than that of columnar crystal region. Reducing laser power could accelerate the CET behavior of melt pool and improve the mechanical properties of coating.