The Effect of Heat Treatment Temperature on Wear Resistance of Ni-B Coating on the C63200 Alloy Applied by Electroless Process

In the present study, in order to increase the wear resistance and surface hardness of Ni-Br-Al alloy, coating process of electroless plating was used to make nickel-boron coating. Microstructural investigations by field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) showed that the nickel-boron coating was uniformly formed with completely amorphous structure, thickness of about 7 µm, and the cauliflower morphology on the substrate. The resulting coating with a hardness of 788 (Hv50) increased the hardness of the substrate by about 40%. To increase the hardness, the coated samples were heat treated at three temperatures of 310, 410, and 510°C for 70 minutes. After the heat treatment, the hardness of the samples increased to 1365 (Hv). By increasing the temperature of the heat treatment from 410°C, the hardness of the samples decreased. XRD results showed that at 310°C temperature, the coating structure was maintained amorphous and at temperatures of 410 and 510 °C, a completely crystalline structure was created. Also, XRD analysis showed the formation of Ni2B and Ni3B precipitates in samples after the heat treatment. According to results of the wear test on the disk, the highest wear resistance was related to the sample coated and heat treated at 410 °C temperature.