Liquid phase surface nitriding of Ti-6Al-4V pre-placed with chromium

• Published in: Materials chemistry and physics 2016-08, Vol.178, p.98-103
• Main Authors: Vahedi Nemani, Alireza, Sohi, M. Heydarzadeh, Amadeh, A.A., Ghaffari, Mahya
• Format: Article
• Language: English
• Subjects: Beta phase; Chromium; Formations; Liquid phases; Microhardness; Microstructure; Surface; Surface treatment; Titanium base alloys; Wear; Wear resistance; Weight loss
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2016.04.075

In this study, liquid phase surface nitriding of Ti-6Al-4V was carried out by pre-placing of chromium powder on the substrate and subsequent Tungsten Inert Gas (TIG) surface melting. The effect of the application of low and high heat inputs on the microstructure, microhardness and wear resistance of the treated layers were studied. Surface alloying with chromium in a nitrogen containing atmosphere resulted in the formation of hard intermetallic compounds such as TiN, Cr2N and TiCr2. Moreover, the presence of beta stabilizer chromium together with the application of high heat input during surface treatment resulted in the presence of beta phase at room temperature. However, applying low heat input could not prevent transformation of beta to martensite. The hardness of the layers fabricated at high and low heat inputs were respectively 1050 and 1200 HV0.3 compared to average 280 HV0.3 for the as-received material. Liquid phase surface treatment of titanium at the aforementioned conditions improved the wear resistance. The lowest weight loss belonged to the specimen with the beta phase matrix. The formation of the fairly ductile bcc-β phase hindered crack nucleation during wear. The weight loss in this condition was 7 times lower than that of the base material. •Liquid phase surface nitriding of Ti-6Al-4V was carried out by TIG surface melting.•Cr powder was pre-placed on the surface as the beta stabilizer alloying element.•The treated layers were characterized by OM, SEM and X-ray diffraction pattern.•Hardness of the layers increased up to 3 times higher than that of the base alloy.•Liquid phase surface alloying improved the wear resistance.