Solar Atmospheres Develops High Temp Vacuum Nitriding Process

According to Don Jordan, Vice President of Technology, “surface hardening of stainless steel is currently one of the hottest topics in the heat treat industry and includes nitriding, carburizing, and nitrocarburizing processes.”  Solar Atmospheres R&D Technology Group is extremely interested in all aspects of this subject and in 2007 successfully performed high temperature solution nitriding of grade 422 martensitic stainless steel at sub-atmospheric pressures (vacuum partial pressure nitrogen).  Surface hardnesses of 59-60 HRC have been readily obtained.

Currently, Solar is engaged in a test program that includes solution nitriding of the martensitic stainless steel grades 410, 420, 422, and 440C.  The variables being studied are nitriding partial pressure, nitriding temperature, and nitriding time.  Tests are being run in a 10 bar high pressure gas quenching vacuum furnace, allowing for the direct quenching of parts from the nitriding temperature (2000-2100°F) to prevent nitride precipitation on cooling. The study will provide information for the development of new surface treatments for improved performance of parts for Solar’s customers.

Above is a near surface photomicrograph of a solution nitrided 422 stainless steel exhibiting a fine dispersion of nitrides / carbonitrides with a hardness of 60 HRC.