Cladding of Ni-Cr-Si-B Powder Coatings by an Electron Beam Injected into the Atmosphere

Abstract

The influence of the cladding rate on the structure and microhardness parameter of coatings obtained by non-vacuum electron beam treatment of Ni-Cr-Si-B powder mixtures was investigated. Modified layers characterized by the gradient structure and consist of dendritic grains and a eutectic located at the grain boundaries. It was found that the lowest microhardness level (300 HV) was characteristic of the coatings obtained when the workpiece was moving relative to an electron beam with a speed of 10 mm per second. This treatment regime allowed obtaining high-quality coatings 2.5 mm in thickness. However, a large thickness of fusion penetration led to the interfusion of the base metal with a coating material and a decrease in the concentration of alloying elements in the coating. Reducing the lifetime of the liquid phase during treatment prevented intensive diffusion processes. Increasing the treatment velocity to 20 mm per second doubled the cladded layer microhardness (up to 650 HV).