Effect of Additions of B and Al₂O₃ Fine Powders on the Densification of SUS316L Steel Powder

Abstract

It has been known B is the most effective sintering enhancer for stainless steel powders. But at the same time, a considerable grain growth was often seen in the sintered compacts containing B. In order to obtain the sintered compacts with high densities and fine-grain structures, 0.2-1.4 mass%Al₂O₃ fine powders were mixed with SUS316L water atomized steel powder, in addition to 0.4 mass% B powders. These mixed powders were compacted and sintered in H₂ atmosphere at 1232-1252°C for 1 hr.
It was shown that the SUS316L steel powder compacts were much more densified during sintering when Al₂O₃ fine powders were added together with B powders, compared with when B powders alone were added. It was considered Al₂O₃ fine powders prevented the formation of isolated large pores which tended to emerge during sintering of SUS316L steel powders containing only B powders, and resulted in the high densification. It was also shown that the tensile strengths of the sintered compacts were fairly improved by the addition of Al₂O₃ fine powders because of its function making the grains finer. The reduction of the elongation causing by the addition of Al₂O₃ fine powders was in allowable ranges.