Nitrocarburizing of Low-Alloy Steels. Influence of Liquid Salt Bath Composition and Surface Layer Constitution and Growth

Samples of UNI 39 NiCrMo 3 and 38 CrAlMo 7 steels have been nitrocarburized with two different proprietary processes, namely the Degussa's Tenifer-TF1 and the Hydromecanique and Frottement's Sur Sulf salt bath treatments. With the former process two different melt compositions were adopted, keeping the CN** minus ions content either at the 0. 5 or at the 4 wt pct level (treatments Tenifer-TF1 A and B). The top surface layer constitution, as determined by X-ray diffraction analysis, is reported for the two steels heat-treated in the Tenifer-TF1 baths in figs. 2 and 3 as a function of the treatment time, whereas the layer thickness growth is depicted in fig. 4.