| 摘要 |
PURPOSE:To form a sprayed deposit excellent in corrosion resistance to molten nonferrous metal by thermally spraying a cermet consisting of metal boride or metal carbide and Ta or Nb onto the surface of a steel member to be in contact with nonferrous metal in a molten state. CONSTITUTION:A thermal spraying robot 11 having a thermal spray gun 15 and a steel stock 13 to be treated, such as conductor roll for use in a hot dip metal coating tank, are disposed in a chamber 1. After the inside of the chamber 1 is evacuated, low-pressure Ar gas is introduced through a supply pipe 7 and a plasma arc is produced by using the thermal spray gun 15 as a cathode and the steel stock 13 to be treated as an anode, by which the surface of the steel stock 13 is cleaned and heated. Subsequently, the polarities of the thermal spray gun 15 and the steel stock 13 are reversed, and, while rotating the steel stock 13, a cermet material prepared by mixing 5-40wt.% of Ta or Nb with ZrB2 or TiB2 is thermally sprayed from the thermal spray gun 15, by which a sprayed deposit in which surface roughness Ra and porosity are regulated to 0.01-5mum and <1.8%, respectively, is formed. By this method, the cermet film excellent in corrosion resistance to molten nonferrous metal, such as Zn, Al, and Sn, and molten alloy can be formed. Further, a cermet in which various metal carbides are used can be used instead of borides, such as ZrB2. |
