Abstract
NiCrBSi and Ni-50Cr coatings are deposited using High Velocity Oxygen-Fuel (HVOF) spray process under different spray parameters with two powders of different sizes to clarify the influence of melting state of spray particles on the adhesive strength of the coating. The adhesive strength of coating is estimated according to ASTM C633-79. The melting state of spray droplet is examined from the coating microstructure. It is found that the melting state of spray particles has significant effect on the adhesive strength of HVOF sprayed Ni-based coatings. The significant melting of spray particle does not contribute to the increase in the adhesion of HVOF metallic coatings. On the other hand, the deposition of partially melted large particle contributes to the substantial improvement of adhesive strength of HVOF coating. The subsequent coating presents a dense microstructure and yields an adhesive strength of over 76 MPa, which is doubled compared to the coating deposited with completely molten particles.
