NiCrBSi coatings by microplasma spraying

The NiCrBSi coatings were deposited onto St37 steel substrates by microplasma spraying (MPS). The influence of the spraying parameters such as substrate temperature, plasma gas flow rate, electric current intensity and spray distance on the microstructure and properties of coatings was investigated by means of statistical experimental design. The coatings were studied in terms of their microstructure using optical microscope. The surface roughness of the coatings was measured by a Perthometers M4P 150. And the oxygen content of the coatings was determined by a LECO TC316 gas extract equipment. The results showed that the spraying parameters influenced significantly on the properties of the coatings. The coating roughness decreased with increasing current intensity and substrate temperature. The oxygen content in the coatings increased with increasing substrate temperature and spray distance. Most of the coatings had a hardness over 600 HV0.2. The coatings exhibited a high bonding strength about more than 50 MPa despite relatively low particle velocities.