Mechanical properties and pitting corrosion behaviour of 316L stainless steel parts obtained by a modified metal injection moulding process

Abstract

Stainless steel AISI 316L parts have been obtained by a modified metal injection moulding (MIM) process using two different thermosetting polymers: commercial acrylic resin and cyclohexyl methacrylate (CHMA). The first resin polymerises at 90 °C while the later cures between 20 and 80 °C. Different mixtures of metal and polymer were investigated and the optimum one was 60 vol.% of metal, for both resins. Due to the fact that the corrosion properties in this type of steel decrease with the carbon content, the debinding cycle has been optimised on the basis of a thermogravimetric study. Sintering was carried out under vacuum atmosphere between 1200 and 1350 °C for 1 h. Mechanical properties were evaluated by means of tensile tests and a good agreement between mechanical properties and sintering curves has been found. Pitting corrosion has been studied through pitting potentials in different chloride environments and at several temperatures. The behaviour of this material has been compared to a wrought 316L and to a conventional powder metallurgy 316L, pressed at 750 MPa and sintered at 1350 °C. The results have been studied on the basis of the carbon content determined by LECO analysis. Pits have also been examined through optical microscopy, to obtain more information about the pitting process.