Effect of heat treatment on the tribological properties of double- layer electroless Ni-P/Ni-B-Bn nanocrystalline composite coating

In this study the effect of heat treatment on the hardness and wear resistance of electroless Ni-P/Ni-B-BN composite Coating was evaluated. Firstly electroless Ni-P Coating layer, with a thickness of 15 microns, and electroless Ni-B-BN coating, with a thickness of 10 microns, on the surface of Ck45 steel samples were deposited, respectively. Samples heat treated at 300, 400 and 500 °C were studied. The effects of heat treatment on the morphology, microstructure and wear behavior of coatings were investigated by means of scanning electron microscopy, X-ray diffraction and pin on disk wear test at ambient temperature. The hardness of the coatings in two states before and after heat treatment were measured by micro Vickers hardness tester and the effect of heat treatment temperature on the hardness of coatings was evaluated.The results of SEM examination showed that the morphology of semi-amorphous structure cauliflower was formed. The X-ray diffraction test revealed that the hard-phase crystallization and deposition of nickel borides (Ni3B) in the nickel. The typical heat treatment at 400° C, had the highest hardness. Pin on disc wear test results prevailed that heat treatment at 400° C reduced the friction coefficient. The heat treatment at 400°C led to a nanocrystalline structure, therefore, the hardness and wear resistance of the amorphous to the crystalline structure and the change in coverage due to the hard phase Ni3B increased.