Heat treatment effect of hexagonal boron nitride reinforced electroless nickel coatings

Abstract

In this study, surfaces of 1050 aluminium alloy were coated with hexagonal boron nitride (h-BN) reinforced electroless nickel-phosphorus (Ni-P) composite coating and the effect of heat treatment on the coating structure for 1 hour at 400°C was investigated. Composite coatings were performed in solutions which consist of three different compositions (1, 5 and 10 g/L) of h-BN. A scanning electron microscope (SEM), X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis were performed on the composite coatings. Additionally, surface roughness and hardness were measured and finally, electrochemical corrosion experiments were conducted in 3.5% sodium chloride (NaCl) solution. The heat treatment process has identified a transition from the amorphous structure to crystalline in the nickel matrix. The result of heat treatment, hardness values increased and the highest value of hardness (1015 ± 41 HV0.05) was achieved with the specimen coated in 10 g/L h-BN solution. In the electrochemical experiments, a reduction in corrosion resistance of the composite coatings was determined as a result of heat treatment.