The influence of Ni concentration on the structure, mechanical and tribological properties of Ni–CrSiN coatings in seawater

Abstract

The impact of Ni content on the microstructure, hardness, fracture toughness and tribological properties of Ni–CrSiN coatings in seawater was investigated by using X-ray diffraction, dynamic ultra micro hardness tester and ball-on-disk tribometer. The structural analyses indicated that the Ni existed in the form of amorphous phase regardless of concentrations. The hardness of Ni–CrSiN coating maintained around 28.1 GPa at low Ni incorporation but decreased to 20.1 GPa at 10.8 at% Ni concentration. Then, owing to grain refinement, the hardness increased to 24.5 GPa at 13.9 at% Ni concentration. All coatings presented compressive stress that led to the formation of circular cracks around indentation impression. The Ni incorporation especially at high concentration was able to improve coatings toughness against circular cracks. Although the Ni incorporation had no effect in reducing the friction coefficient of CrSiN coatings in seawater, but the moderate Ni incorporation (5.2 at%) could enhance the wear resistance of CrSiN coatings in seawater due to the favorable combination of hardness and toughness.