Effect of spray distance on the mechanical properties of plasma sprayed Ni-45Cr coatings

Ni-45Cr coating was plasma sprayed at different spray distances in order to clarify the influence of spray distance on the mechanical properties. The mechanical properties of Ni-45Cr coatings include the fracture toughness, elastic modulus and Poisson's ratio parallel to lamellar plane. The fracture toughness of plasma-sprayed Ni-45Cr coating in terms of critical strain energy release rate (G_lc) was investigated using a tapered double cantilever beam approach. The elastic modulus and Poisson's ratio parallel to lamellar plane,were obtained by measuring the relation of stress and strain using strain gauges. It was found that the fracture toughness of plasma sprayed Ni-45Cr coatings was not significantly influenced by spray distance up to 190mm and further increase in spray distance to 210mm resulted in an evident decrease in the fracture toughness of the coatings. Moreover, spray distance showed minor effect on the elastic modulus and Poisson's ratio parallel to lamellar plane of Ni-45Cr coating. The examination of fractured surface revealed that the fracture toughness of plasma-sprayed Ni-45Cr coatings is related with the lamellar bonding.