Microstructure and property evolution during the sintering of stainless steel alloy with Si 3N 4

Abstract

This paper describes the sintering of a martensitic stainless steel alloy with addition of Si 3N 4. Sintering behavior was studied at different sintering temperatures ranging from 1250 to 1400 °C with different holding times (20–80 min) and with varying Si 3N 4. Results showed that the samples were densified rapidly via liquid phase sintering mechanism. Nearly full density was obtained at 1300 °C after 60 min of holding time with 5 wt% Si 3N 4. Temperature above 1350 °C and Si 3N 4 content 10 wt% caused slumping of the samples. Two weight percent Si 3N 4 was found chemically stable in steel alloy. Above 2 wt% Si 3N 4 dissolved in the steel matrix. The distribution of dissolved Si and N was characterized by XMAP. When N content reached much above its solubility limit in steel alloy it diffused out leaving pores in steel alloy with considerable decrease in the sintered density. The mechanical properties of the sintered product with varying Si 3N 4 were measured. A maximum ultimate tensile strength of 1011 MPa was achieved with 2 wt% Si 3N 4 sintered at 1300 °C after 60 min of holding time. Fracture morphologies of tensile samples are also reported.