INVESTIGATION OF MECHANICAL AND TRIBOLOGICAL CHARACTERISTICS OF Ni-B COATINGS DEPOSITED ON STEEL

Abstract

In this study, mechanical properties and wear behaviors of Ni-B coatings were investigated. The mechanical and wear properties of the coating change depending on the nickel boride (Ni2B and Ni3B) phases formed after heat treatment at 400oC for 2 hours. Nodular structure formed in the surface morphology and columnar growth in the cross-sectional images of the coating as-deposited and annealed was examined by scanning electron microscopy (SEM). The amorphous structure at as-deposited and the nickel boride phases formed in the structure after annealing were analyzed by X-ray diffraction (XRD). Using the Debye-Scherrer formula, the effect of the phases formed in the structure on the crystalline grain size after annealing was calculated. The hardness values of the coating as-deposited and annealed were calculated by nano-indentation hardness measurement method. Wear tests of the coatings, which were subjected to heat treatment at 400oC for 2 h, were carried out in dry conditions without the use of lubricants, at different loads (1N-3N-5N), at a sliding speed of 25 mm/s and at 25oC. After the wear tests, the wear surfaces of the samples were imaged by SEM and their chemical compositions were analyzed by energy dispersive spectroscopy (EDS). The wear rate and coefficients of friction the samples tested under different loads had compared each other.