Microstructure of the deposited NiCrBSiC coating after laser polishing

Abstract

The structure of the surface layers of NiCrBSiC coatings obtained by powder laser cladding and subsequent laser polishing with a multichannel CO 2 laser has been studied. XRD and TEM / STEM showed that the coatings are a γ-Ni matrix with Ni 3 B, Cr 3 C 2 and Ni 3 Si precipitates. It was shown that the matrix of the coating after laser cladding has a high density of dislocations, which form networks. XRD evidences a decrease in the number of the precipitates after laser polishing and TEM / STEM demonstrated a decrease in the density of dislocations and the appearance of nanostructured γ-Ni layers in the form of flat elongated plates. The width of nano-grains is ≈20 nm near the interface and increases with distance from it. Microhardness measurements showed an increase from 4.4 to 5 GPa after laser polishing.