PLASMA NITRIDING OF TI AND TI-AL COATINGS

The Ti and Ti-Al coatings were deposited onto hot-worked AISI H11 stee l substrates and plasma nitrided at 900-degrees-C. The Ti coated sampl es were successfully nitrided, while cracking and delamination of the Ti-Al coating was observed during nitriding. The formation of delta-Ti N and epsilon-Ti2N phases were detected after plasma nitriding of the Ti coating. During plasma treatment of the Ti-Al coating, the initial Ti3Al and Al phases were partially transformed into TiAl phase. The ma rtensite transformation of the substrate material was found. The as-de posited Ti coating has a fibrous structure, while the structure of the as-sputtered Ti-Al coating is columnar. The superficial Vickers micro hardness of plasma-nitrided Ti coating was 2200 HV 0.03 and the critic al load of higher than 50 N indicates very good coating-to-substrate a dhesion.