High Temperature Oxidation and Tribological Behaviors of NiCrAl-Graphite Self-Lubricating Composites

Nickel-graphite self-lubricating composites are a promising candidate to be used in turbine constructions that are usually exposed to high temperature oxidation and wear.However,the high-temperature stability of graphite as well as the effect that the oxide scale will play on the following wear process are still yet in debate.In this work,oxidation behavior of a NiCrAl-graphite composite and the subsequent friction and wear performances were studied.Results indicate that graphite is stable in the composites after oxidation at T≤400℃ for 300 h,which contributes synergistically with the thin oxide film to self-lubrication.The friction coefficient is below 0.20 and the wear rate is~1.43×10^(-5) mm³ N-1 m-1.The composite has the highest friction coefficient and wear rate when it was suffered from the high temperature oxidation at 500℃.Once it was oxidized at 600℃,a glaze layer would develop during the subsequent sliding.It plays a positive role in improving tribological properties though in the absence of lubricant phase of graphite,with to be exactly the friction coefficient and wear rate reduced by 13%and 21%,respectively,in comparison with the case of oxidation at 500℃.