Volume 8, Issue 1 (January 2011)
Characterization of Highly Hardened Surface Layers on Austenitic Stainless Steels
The highly hardened surface layers obtained from a TiN-physical vapor deposition (PVD) coating and a treatment that leads to a surface carbon enrichment, applied to American Iron and Steel Institute (AISI) 304, 316, and 316L stainless steels, have been characterized. The metallographic analyses have revealed a depth of about 2.5 μm for the TiN-PVD treatment (1150 HV) and of between 30 and 40 μm for the carbon enrichment (1000–1150 HV), depending on the steel composition. The molybdenum enhancing carbon diffusion is also discussed. The X-ray diffraction analysis has shown an increase in the lattice parameter, subsequent to insertion of the carbon interstitial element, a reduced Fe5C2 Hägg carbide precipitation (mainly on AISI 304 samples), and high compressive stresses. The carbon profiles, obtained on carbon enriched samples through microprobe analysis, have been related to the HV profiles.