18th International Conference on Surface Modification Technologies; Dijon; 15 November 2004 through 17 November 2004; Code 67119 - Microprobe characterization of nitrocarburized surface layers.

The present study aims to analyse by microprobe the phases obtained in sintered steel samples nitrocarburized in a gaseous atmosphere at 730°C, by means of a mixture of ammonia-methanol (15%) with a previous sulfoxidizing treatment, executed with sulfur dioxide at 500°C, in order to close the surface porosity. The alloying elements in samples are: C (0.01, 0.50 and 0.76%), Ni (4 and 7%), Cr (1.5%), Mo (0.5%), Cu (0.5 and 2%) and Al (1%). The surface hardened layers present remarkable thickness and are constituted by the s solid solution, the γ′-Fe4N carbonitride, martensite and austenite. The surface layers are characterized by X-ray diffraction analyses, effected at different depth, by grinding the surface layers, in order to evaluate the relationship of the phase types and percentages with the depth in the compound layers. Microprobe analyses evidence a partition of alloying elements in the different phases, more evident in the γ′- carbonitride and in martensite than in the ε solid solution and in austenite.