Wear analysis of D.C. pulsed plasma nitriding of AISI 4340 low alloy steel for crankshaft application

The aim of this research work was to carry out the pulsed plasma nitriding of AISI 4340 low alloy steel in a Direct Current (D.C) glow discharge system by varying the plasma nitriding temperature and time while keeping pulse duration as constant. The benefit effect of controlling the pulse duration is to avoid the continuity of electrical charges with the ions and the substrate thereby reducing the formation of compound layer which in turn avoids the brittleness and its later side effects, and also to have the homogeneity in temperature and for energy savings. The results were characterized by micro hardness measurements followed by case depth analysis by hardness mapping from case to core and surface profilometry analysis for surface roughness measurements. The microstructure of the compound layer was examined by optical microscope, and the Scanning Electron Microscope (SEM) with Energy Dispersive Spectrometer (EDS) and X-ray Diffraction (XRD) studies were employed to analyse the compound layer morphology and its properties. The wear rate was examined by using Pin on disc test and its results were analysed by SEM and EDS. The tailored properties were obtained and the process parameters were optimized for sustained usage. The broad application of usage of this method to enhance the fatigue life of the rotating part such as crankshaft, shafts when compared with gas nitriding and induction hardening.