Characterization of WC-doped NiCrBSi coatings deposited by Laser Cladding; effects of particle size and content of WC powder

Tungsten carbide doped NiCrBSi coatings have been deposited by Laser Cladding (LC) on steel agricultural knives in order to improve their life time. The influence of the mass fraction as well as the particle size of the tungsten carbide powder on structure, microstructure and mechanical properties was analyzed. The mechanical characteristics were studied from micro-hardness tests, pin-on-disc wear tests and cutting tests of plant material. The coating hardness is stable when carbide powder content in the mixture is between 35 and 60 wt%. Then this hardness increases significantly when the carbide content reaches 70 wt%. The wear coefficient in dry conditions decreases when the carbide powder content is increased from 35 to 40 wt%. Further increase of the carbide powder content in the mixture does not affect the wear coefficient. The coating hardness increases with the particle size of the carbide powder. The cutting test shows that the finest particle size (20–53 μm) of the carbide powder leads to the lowest values of the cutting-edge wear and the mass loss. This is attributed mainly to the better volume distribution of tungsten carbide particles as well as to the resistance of the matrix due to precipitation of the Ni4W phase.