PLASMA NITRIDING OF MICROALLOYED STEEL

Microalloyed or high strength low alloy (HSLA) steels are carbon-manga nese steels containing small amounts of Nb, V or Ti. The excellent mec hanical properties of these alloys, particularly high yield strength, usually obviate the need for expensive quench and tempering operations . Furthermore, the presence of a significant amount of nitride-forming elements in some microalloyed steels has generated interest in the ap plicability of these alloys as a new generation of nitriding steels. I n this paper, a study of the plasma nitriding behaviour of a commercia lly available microalloyed steel MAXIMA(TM) is reported. A comparison is made with a traditional quenched and tempered nitriding steel(En19) , plasma nitrided under similar conditions. Optical and scanning elect ron microscopy in conjunction with microhardness measurements and X-ra y diffraction were utilized to characterize the nitrided surfaces. The observed differences in the thickness and structure of the compound l ayer and the diffusion zone are discussed in terms of chemical composi tion and microstructure of these steels.