The influence of temperature on the wear of Cr3C2-25(Ni20Cr) coating-comparison between nanocrystalline grains and conventional grains

CrxCy-NiCr coating is commonly used in the industry for protection against wear at elevated temperature. With an aim to investigate the friction behaviour of this layer at elevated temperature, Cr3C2-25(Ni2OCr) coating with nanocrystalline grains and with conventional grains are deposited on 253 MA alloy using JP-5000 high velocity oxy fuel (HVOF) system. The coating microstructure was characterised using X-ray diffraction (XRD), scanning electron microscopy and micro hardness measurements. The wear and friction behaviour of this coating against 100Cr6 steel are studied and compared for a range of temperature up to 1073 K with the help of an high temperature friction and wear rig. The mechanisms of wear are characterised using SEM. Both coatings exhibited excellent wear resistance under the test conditions. The coating with nanocrystalline grains exhibited minimum friction coefficient at 873 K whereas coating with conventional grains had minimum friction coefficient at 1073 K. This behaviour is attributed to the formation of a thick soft transfer layer on the wearing surface of the coating with nanocrystalline grains.