Hardness and Wear Resistance of Ni-B Alloy Coatings

Ni-B alloy coatings were prepared on copper substrate by constant current electroplating method from the electrolyte system with nickel sulfamate as main salt and sodium borohydride as boron source,and pure Ni coating and Ni-Fe alloy coating were prepared using similar method as control samples.Ni-B alloy coatings were heat treated in vacuum annealing furnace.The crystal structure and surface morphology were characterized by X-ray diffractometer and scanning electron microscopy,and the hardness and wear resistance were tested by microhardness tester and friction wear testing machine.Wear cracks morphology of the coatings were observed,and then the wear mechanisms were analyzed.Results showed that Ni-B alloy coatings featuring bright and smooth surface,the hardness reach up to 7000~8000 MPa. Furthermore,higher hardness value of about 11 000MPa can be obtained after heat treatment at 300℃.Compared to pure Ni coating and Ni-Fe alloy coating,Ni-B alloy coatings present better wear resistance.