Nitrogen Diffusion at Low Temperature in fcc Materials Deformed by Attrition Peening

Recent scientific work has opened new fields of application to mechanical treatments such as shot blasting or peening. Indeed, it has been shown that this treatment, performed before a nitriding treatment on the surface of ferrous alloy, lowers processing temperatures and significantly increases the diffusion kinetics. We undertook to test this combination of mechanical pretreatment and thermochemical treatment on stainless steels and nickel-based alloys. The mechanical treatments were done by surface attrition peening. The pretreated samples were then nitrided at low temperature using remote plasma. In this paper, the results obtained after nitriding treatments on samples treated by attrition peening are compared to those nitrided only. The use of X-ray diffraction, microhardness measurement, observations by optical and scanning electron microscopy, texture analysis by EBSD (Electron BackScatered Diffraction) and measurement of nitrogen concentration profiles by SIMS (Secondary Ion Mass Spectrometry) allows quantifying the effects of the combined treatments.