Mechanical Properties and Corrosion Resistances of P/M Two-phase Stainless Steels with Silicon.

Influence of the addition of silicon on mechanical properties and corrosion resistances of P/M austenitic stainless steels was investigated by means of microstructual examinations, calorimetric analysis and X-ray analysis. Silicon addition to P/M austenitic stainless steels makes the sintering in the duplex structure of austenite(γ) and ferrite(α) possible by the liquid phase sintering with a eutectic liquid. For example, addition of 4mass% Si results in the formation of about 40vol% of ferrite. Tensile strength of sintered steels increases with increased silicon content, and the maximum strength (940MPa) was obtained in the steel with 4mass%Si which was sintered for 3.6ks at 1623K. On the other hand, elongation of sintered steels tends to increase with rising sintering temperature. The maximum elongation (47.5%) was obtained in the steel with 2mass%Si which was sintered for 3.6ks at 1673K. The sintered steel with 2mass%Si was found to have excellent corrosion resistance in a boiling solution of 65% HNO3 : The corrosion rate of the steel was very small in comparison with the sintered SUS304L steel, but it was three times larger than that of a SUS304L steel produced by ingot metallurgy. However, further addition of silicon causes a decline in corrosion resistance probably due to a decrease in the green density.