Preparation and wear performance of NiCr/Cr3C2-NiCr/hBN plasma sprayed composite coating

Abstract

NiCr clad hexagonal BN powder (NiCr/hBN) was added to NiCr/Cr3C2 feedstock to improve the tribological properties of chromium carbide nichrome coating. The microstructure, flowability and apparent density of the composite powder, as well as the structure and mechanical properties of the plasma sprayed coating were characterized. The friction and wear behavior of the NiCr/Cr3C2-NiCr/hBN coating from ambient temperature up to 800 degrees C was evaluated on a ball-on-disk wear tester and compared with that of NiCr/Cr3C2 coating and NiCr/Cr3C2-NiCr/BaF2-CaF2 coating. The results show that NiCr cladding can reduce the decarburization of Cr3C2 and oxidation of hBN during the thermal spray. The main wear mechanisms of the NiCr/Cr3C2-NiCr/hBN composite coating are ploughing and adhesive wear. Layered hexagonal BN particle reduce the direct contact and severe adhesion between friction pairs, thus decreasing the friction coefficient. The NiCr/Cr3C2-NiCr/hBN composite coating shows a promising application in the high temperature environment with the request of both wear resistance and friction reduction. (C) 2011 Elsevier B.V. All rights reserved