The effect of the deposition temperature and activator concentration on the structure of NiCrBSi coatings deposited on low carbon steels by pack cementation process

Abstract

The feasibility of NiCrBSi powder deposition on low alloy steels with pack cementation is investigated at different temperatures (800–1000 °C) and with various halide salt activator content in the pack powder (1–6 wt.%), while the deposition time was set at 4 h. The as-coated samples were examined with Scanning Electron Microscopy (SEM) associated with Energy Dispersive Spectroscopy (EDS), and X-Ray diffraction analysis (XRD). It was revealed that both parameters affect the coating thickness, but not the phase composition of the as deposited coating, which in every case is composed by a Cr 2O 3 thin layer on the top, which enhances the corrosion resistance and Cr–B, Ni–B and Fe–Ni phases in the rest of the coating which increase the hardness and wear resistance. The activator content has also effect on the coating quality and integrity. In cases where its concentration is low or at higher levels (> 6%wt.) the as formed coatings are inhomogeneous and of low cohesion.