Development of New Modified "super Saturated NitroCarburizing" for Modern High Pressure Injector in Powertrain

The aim of this work is to investigate the current carburizing heat treatment and subsequently to develop new modified heat treatment with increase of surface hardness and corrosion resistances for next generation of injector parts. Considered parts are stopper (SUS303) and position ring (1.4305) of high pressure injector in powertrain. At first, current carburized components are investigated and resulted: hardness (HV_{100 mN}) 802-959, layer thickness of 17.85-24.59 μm, corrosion resistance was maximum 1 hour at 8.25% NaClO solution. New modified heat treatment is Super Saturated NitroCarburizing (SSNC) which is generated with nitrogen and carbon sourcing gas in temperature range of 350-450°C. The process in detail is: nitrogen purging and heating, activation at 360°C for 1 hour, heating, nitrocarburizing at 450°C for 9 or 12 hours, and cooling. The nitrogen rich S-phase was formed at surface and carbon rich S-phase was formed at subsurface. As a result, the SSNC layer had 1,316-1,407 HV_{100 mN}, thickness of 20.4-22.95 μm. Their corrosion resistance was approximately 3.5 times more resistant than the current one. In conclusion, the new modified SSNC heat treatment showed higher hardness of at least 300 HV_{100 mN} and 3.5 times better corrosion resistance than current carburizing.