Post-sintering thermal treatment of nitrogen containing pressed and sintered and PIM stainless steels

• Published in: Powder metallurgy Vol. 50; no. 2; pp. 165 - 171
• Main Authors: Hwang, K. S., Hsueh, Y. W.
• Format: Journal Article
• Language: English
• Published: London, England Taylor & Francis 01.06.2007; SAGE Publications; Maney; Taylor & Francis Ltd
• Subjects: Applied sciences; CHROMIUM NITRIDE; COOLING RATE; CORROSION; Corrosion environments; Exact sciences and technology; Metals. Metallurgy; NITROGEN ATMOSPHERE; POWDER INJECTION MOULDING; POWDER METALLURGY; Powder metallurgy. Composite materials; Production techniques; Sintered metals and alloys. Pseudo alloys. Cermets; SINTERING; STAINLESS STEEL; Technology; POWDER METALLURGY; STAINLESS STEEL; POWDER INJECTION MOULDING; CORROSION; CHROMIUM NITRIDE; SINTERING; NITROGEN ATMOSPHERE; COOLING RATE; Heat treatment; Nitrogen atmosphere; Cooling rate; Chromium nitride; Sintered steel; Nitrogen; Powder metallurgy; Corrosion; Powder injection moulding; Powder injection; Stainless steel; Sintering; Chromium; Injection molding
• ISSN: 0032-5899; 1743-2901
• DOI: 10.1179/174329007X164853

It is known that nitrogen in the sintering atmosphere impairs the corrosion resistance but enhances the strength and hardness of sintered stainless steels. In this study, an additional post-sintering thermal treatment was applied on parts that were sintered in N 2 containing atmospheres and its effects on the mechanical properties and corrosion resistance were evaluated. Both pressed and sintered (P/S) 304L and powder injection moulded (PIM) 316L stainless steel compacts were examined. The results show that the Cr 2 N compound was formed throughout the low density 304L compact, causing poor corrosion resistance when there was nitrogen in the sintering atmosphere. However, the high density PIM 316L compact only contained Cr 2 N at the surfaces owing to the high sintering temperature and the lack of interconnected pores. This Cr 2 N compound can be suppressed when the compact is reheated to 1100°C in argon and then cooled at a moderate rate of 57°C min −1 . With this post-sintering treatment, even the compact sintered in pure nitrogen showed satisfactory corrosion resistance results, similar to those of hydrogen sintered compacts.