Abstract

The surface characteristics of CF8 stainless steel materials for shell mold cast and investment cast were studied, including surface composition, roughness and reflectivity. We report their changes are governed by the solution annealing, casting and passivation treatment. As for the surface composition, Chromium (Cr) portion decreased initially but showed increasing tendency at time passed in passivated shell mold cast. However, nickel (Ni) portion increased initially but revealed decreasing tendency at time passed. This implies the surface film becomes the chromium-rich oxide phase at optimum condition. The optical reflectivity of solution annealed and passivated surface increased by 16% compared to the basis metal case. When the optimum chemical passivation was applied, the surface roughness showed the lowest value in shell mold cast. This may indicate that the corrosion resistance of CF8 material can be improved by solution annealing followed by optimized chemical passivation.

Keywords: CF8 stainless steel; Reflectivity; Roughness; Corrosion resistance