Metastable phase evolution and nanoindentation behavior of amorphous Ni–Cu–P coating during heat treatment process

Abstract Effects of heat treatment on the microstructure evolution and phase transition of the Ni–Cu–P amorphous coating, prepared through electroless plating, were investigated by X–ray diffraction (XRD) and transmission electron microscope (TEM). It is found that the metastable Ni 5 P 4 , Ni 12 P 5 and Ni 5 P 2 phases were precipitated during the annealing process, which were transformed into stable Ni 3 P phase after crystallization. Cu atoms in the Ni–Cu–P amorphous coating was precipitated in the form of Ni(Cu) solid solution. Besides, the mechanical properties of the Ni–Cu–P coating during crystallization was systematically studied by nanoindentation measurements. The results showed that the hardness, elastic modulus and wear resistance of the coating were significantly affected by the microstructure evolution and phase transition during the crystallization process.