MICROSTRUCTURAL STUDIES OF QPQ COMPLEX SALT BATH HEAT-TREATED STEELS

QPQ salt bath surface treatment has been developed successfully in Chi na, introducing a new salt to the bath and offering superior surface p roperties such as high hardness, good wear-resistance, improved fatigu e resistance and very good corrosion resistance for the treated compon ents. In recent years the method has been used widely: for tools and m oulds to increase their strength and to extend their life; for gears t o increase their strength, wear-resistance and fatigue strength and to secure less distortion; for automobile parts to increase their wear-r esistance and corrosion resistance; also for PCB parts to increase the ir hardness, wear resistance and corrosion resistance and to reduce th eir distortion. This article emphasizes the microstructural and compos itional analysis, and also the effects of temperature and process dura tion on the depth of the nitrided layer. (C) 1997 Elsevier Science S.A .