On the nature, properties and wear response of s-phase (nitrogen-alloyed stainless steel) coatings on AISI 316L

Nitrogen-alloyed AISI 316L coatings with nitrogen contents, [N], between 1.2 and 80 nitrogen atoms per 100 metal atoms (N/100 Me) were obtained by reactive sputter deposition. Coatings comprising only a nitrogen supersaturated metastable face-centred cubic (fcc) phase (s-phase) were obtained for 8.6 less than or equal to [N] less than or equal to 48 N/100 Me. For [N] less than or equal to 5.8 N/100 Me body-centred cubic (bcc) phases were present in the coatings while at [N] greater than or equal to 65 N/100 Me the coatings comprised unidentified high nitrogen phases in addition to s-phase. The lattice parameter of the fully a-phase coatings increased linearly with increasing [N] according to a = 0.3585 + 0.00075 [N] nm The hardness of the s-phase coatings attained a maximum value of approximate to 20 Cpa at [N] approximate to 30-40 N/100 Me. The nitrogen in the s-phase coatings reduced the wear of the coatings by 1-2 orders of magnitude compared to the wrought material by promoting an oxidational wear mechanism.