Influence of Sintering Atmosphere in the Hardness and Corrosion Resistance of 17-4 PH Stainless Steel Shaped from Powder Injection Molding Process

Abstract

Abstract The powder injection molding process is used to manufacture parts with complex shapes and high production demand. In orthodontic and medical applications, in which high hardness and corrosion resistance are required, 17-4 PH stainless steel is used mainly by this forming technique. The sintering atmosphere is responsible for controlling the chemical reactions that occur during material densification and is critical to the ultimate product quality. This research evaluated the influence of the sintering atmosphere on the hardness and corrosion resistance of this type of steel. The removal of the primary binder was conducted by chemical extraction by using a solvent with less environmental impact which has proved to be suitable for this purpose. The subsequent binder thermal extraction was performed by heating at temperatures of 250 and 450 °C and afterwards to 900 °C to initiate sintering. Nitrogen, vacuum and hydrogen atmospheres were used with sintering temperatures at 1250 and 1330 °C with 30 and 60 minute time step. It was shown that the densities achieved in hydrogen and vacuum atmospheres are similar and suitable by the regulations, whereas the nitrogen atmosphere resulted in lower performance. The hardness and corrosion resistance obtained with the use of hydrogen and vacuum atmospheres were also higher than those obtained for samples sintered in the nitrogen atmosphere.