Crystal Structure and Mechanical Properties of Nitrided Stainless Steel Coatings Deposited by Arc Ion Plating

• Published in: Hyōmen gijutsu Vol. 52; no. 12; pp. 860 - 865
• Main Authors: KATOH, Jun, SATOH, Toshiki, YAMAMOTO, Kenji
• Format: Journal Article
• Language: English; Japanese
• Published: Tokyo The Surface Finishing Society of Japan 01.12.2001; Hyomen Gijutsu Kyokai; Japan Science and Technology Agency
• Subjects: Arc Ion Plating; Crystal Structure; Mechanical Property; Nitrogen; Stainless Steel
• ISSN: 0915-1869; 1884-3409
• DOI: 10.4139/sfj.52.860

Nitrogen containing stainless steel coatings were deposited on cemented carbide substrates by arc ion plating at various nitrogen partial pressures using SUS 304 (AISI 304) and SUS 430 (AISI 430) targets. The effect of nickel and nitrogen content on the crystal structure and mechanical properties of coatings were studied. The SUS 304 coatings consisted of nitrogen-supersaturated fct-γ phase with nitrogen content up to about 35at%. Additionally, fine grained Fe3N (ε) phase started to precipitate at nitrogen content above approximately 20at%. The SUS 430 coatings mainly consisted of (Cr, Fe)2N1-x(ε') phase. The hardness of the coatings increased uniformly with the nitrogen content and a maximum hardness value of Hv 1100 was obtained at a nitrogen content of about 35at%. This increase in hardness can be due to the lattice distortion caused by nitrogen atoms at interstitial sites in supersaturated Fe-N solid solution and the precipitation of fine grained nitrides. The tipping resistances of SUS 304 coatings which were determined by scratch tests showed a constant value of more than 200N, independent of the nitrogen content and the precipitation of ε phase. Contrary to this, those of SUS 430 coatings were approximately 20N, which can be due to the formation of ε' phase. Nickel may suppress the formation of ε' phase and contribute to the superior toughness observed. The nitrogen-supersaturated γ phase deposited by arc ion plating is considered to have a structure similar to that of the γN phase deposited by sputtering and YN phase by plasma nitriding.