Effect of Boron and Silicon Additions on Liquid-Phase Sintering Behavior and CorrosionResistance of PIM Ferrite Type Stainless Steels

摘要

The effect of boron (B) and silicon (Si) additions on the liquid-phase sintering behavior and corrosion resistance of PIM ferrite type stainless steel (SUS430L) was investigated. As a result, the addition of B improved the sintering of specimens, and the relative sintered density of 0.2mass percent B and 0.2mass percent B + 2mass percent Si added steel sintered at 1573K were more than 97 percent. The high tensile strength was obtained on 0.2mass percent B +2mass percent Si added specimens sintered at 1473, 1523 and 1573 K, and the maximum strength was 508MPa obtained at 1573 K. The reason was considered due to the high density of the matrix obtained by the eutectic reaction between the matrix and borides and the solid-solution hardening of matrix by Si element. On the other hand, the ductility was not improved by the addition of B and Si. This results may be due to grain coarsening and borides precipitated along the grain boundary. The specimen with 0.2mass percent B and 0.2mass percent B + 2mass percent Si sintered at 1573 K were found to have an excellent corrosion resistance in a pitting corrosion t(.-5t of a solution of 6 percent FeCl_3 (N/20 HCl). Especially, the corrosion rate of the 0.2mass percent B + 2mass percent Si added steel sintered at 1573K is smaller by one sixth compared of the non-added steel. However, in the case of steels sintered at lower than 1523 K, the corrosion resistance of 0.2mass percent B and 0.2mass percent B+2 mass percent Si added steels was similar to that of the non-added steel. This tendency was probably due to a low sintered density in similar to the non-added P/M steel.