the effects of nitriding parameters in hot working steel aisi h13 on its surface properties and nitride layers during conventional and active screen plasma nitriding treatments

the main aim of this research was to investigate the effects of plasma nitriding parameters including frequency and duty cycle for a seris of test samples with different grooves during conventional plasma nitriding (cpn) and active screen plasma nitriding (aspn) treatments. the sample assemblies were consisted of rectangular grooved steel blocks with different groove dimensions of 2, 4, 6, 8 and 10 millimeters (width), 40 millimeters (height), and 20 millimeters (length) and aisi h13 steel plates (as the substrate material) with dimensions of 10 40 60 mm3. the sample assemblies were processed in conventional and active screen plasma nitriding chamber at the atmosphere of 75%h2-25%n2 with the temperature of 500 °c, the duty cycles of 40, 60, 80%, and the frequencies of 8, 10 khz for 5 hours. the properties of processed substrates were investigated through the evaluation of the compound layer thickness, case depth, phase composition as well as the hardness profile. the results showed that the hallow cathode effect occurs during cpn method for a sample with 2 mm width groove and the duty cycle of 80% leading to the overheating of the sample. the surface morphology of the cpn treated samples was consisted of cauliflower shaped surface nitrides while the surface of the aspned samples were covered by the hexagonal particles with a uniform distribution.