Effect of WC content on laser cladding Ni-based coating on the surface of stainless steel

Abstract

Ni-based cladding coatings with WC weight percentage of 5%, 7.5% and 10% were prepared on the surface of 0Cr17Ni12Mo2 stainless steel by Raycus RFL-C1000 laser, and optical microscope, scanning electron microscope, energy spectrum analyzer, X-ray diffractometer, microhardness instrument, electrochemical analyzer, friction and wear test machine and wear track measuring instrument were used to characterize the microstructure and properties of the coatings. The results showed that the coating microstructure was mainly composed of cellular crystals and columnar crystals，and due to the combined effects of convection and rapid solidification of laser in the molten pool, WC granules were unevenly distributed and had "agglomeration" effect. With the increase of WC content, the nucleation core in the coatings saw an increase, and the degree of grain refinement raised. In addition, the coatings obtained higher thermodynamic stability and microhardness with the increase of WC content. However, as the number of unevenly distributed WC granules acting as primary batteries added, the tendency of corrosion reaction was enhanced and the corrosion rate increased initially, followed by a decrease. Owing to the influence of solid solution strengthening, dispersion strengthening and surface defects such as cracks and pores, the wear volume and friction coefficient of the coating showed a trend of first growing and then dropping with the increase of WC content.