PM304 coating on a Ni-based superalloy rod for high temperature lubrication

PM304 coating on a Ni-based superalloy rod for high temperature lubrication has been prepared by high-energy ball milling and powder metallurgy techniques. The composition of the PM304 coating is the same as that of PS304 coating, but the microstructure is quite different. The microstructure of PM304 coating is fine and dense; the size of self-lubricating particles in the coating is very small. Self-lubricating Cr2O3 particles are about 100 nm, BaF2/CaF2 particles about 1 μm, Ag particles below 5 μm, while BaF2/CaF2 and Ag particles precipitated from NiCr matrix are less than 50 nm. The fine and dense microstructure results in increased tensile strength and crack growth resistance of PM304 coating. The mean tensile strength is about 46 MPa.