The Effect of Nitrogen Flow Rate on the Loadbearing Capacity from Nano- to Macro-Hardness of Austenitic Stainless Steels Magnetron Sputtering-Coated with Stainless Steel Films

Abstract

UNS S31603 stainless steel (SS) substrates were covered by reactive magnetron-sputtering with protective SS coatings of the same steel specification. A mechanical characterization study (through nano-, micro-and macro-hardness tests) of samples obtained under two different sputtering conditions and varying the N 2 gas flow rate was carried out. This contribution aimed at appraising the effects of varying the nitrogen flow rate on hardness, elastic modulus, and susceptibility to indentation-induced crack formation of the coated SSs. Nitrogen-free samples displayed body-centered cubic (BCC) films with 9.0-9.4 GPa hardness and 203-206 GPa elastic modulus, while their susceptibility to indentation-induced cracking varied between superior and moderated among the two sets of sputtering conditions studied. Samples alloyed with 4-6 N at-% displayed a predominantly face-centered cubic (FCC) structure, 9.4 GPa hardness, 196-218 GPa elastic modulus, and superior resistance to crack formation. Samples with 11.5-22.0 N at-% were fully composed of the FCC structure, displayed 12.4-15.2 GPa hardness, 188-193 GPa elastic modulus, and moderated resistance to indentation-induced crack formation. Samples with 47.0 N at-% displayed FCC compound nitride structure, for which hardness and elastic modulus were 8.1 GPa and 139 GPa, respectively. These samples displayed low resistance to crack formation.