Formation of layers by plasma nitriding imposed to 32CrMoV13 low alloy steel

Abstract

The aim of the study is to optimise the application of heat treatments by modifying the nitriding conditions in high temperature process. The influence of gas mixture (composed of N2, H2 and CH4) and time of nitriding on the mechanical and structural properties of 32CrMoV13 low alloy steel samples was studied. The composition and structure of the nitrided layers was determined by EDS and XRD respectively. Vickers micro hardness profiles were also performed to study the influence of the gas mixture and time of nitriding. The morphology of the nitrided layers was observed by optical microscopy. EDS analyses permitted to verify the composition of the layers while their structure was determined by XRD. The time of nitriding was influent on the diffusion layer’s thickness and properties. Furthermore, it was obvious that increasing the nitrogen contents from 20 to 80 % in the nitriding gas mixture N2+H2 or adding 5% of methane permits to increase the nitrided layer’s thickness and hardness. The duplex treated samples obtained with 80 % of N2 or 5% CH4 performed best and allowed to increase almost twice the tools service life.