Abstract
Experiments were performed with an aim of studying the effect of hot-rolled temperature (600 and 900A degrees C) on radio frequency (rf) plasma nitriding of Fe93Ni4Zr3 alloy. Nitriding was carried out for 10 min in a nitrogen atmosphere at a base pressure of 10(-2) mbarr. Different continuous plasma processing powers of 300-550 W in steps 50 W or less were applied. Nitrided hot-rolled specimens were characterized by optical microscopy (OM), X-ray diffraction (XRD) and microhardness measurements. The results reveal that the surface of hot-rolled rf plasma nitrided specimens at 600A degrees C is characterized with a fine microstructure as a result of the high nitrogen solubility and diffusivity. Moreover, the hot-rolled treated samples at 600A degrees C exhibit higher microhardness value than the associated values of hot-rolled treated samples at 900A degrees C. The enhancement of microhardness is due to precipitation and predominance of new phases (gamma and epsilon phases). Mainly, this conclusion has been attributed to the high defect densities and small grain sizes of the samples hot-rolled at 600A degrees C. Generally, the refinement of grain size plays a dramatic role in improvement of mechanical properties of tested samples.