High pressure gas quenching: Distortion analysis in gears after heat treatment

The analysis of distortions, hardness level and microstructure of the surface layers of the toothed gears after low pressure carburizing and high pressure gas quenching is presented in this paper. Toothed gears of module 2 made of 16MnCr5 steel, case carburized to depth 0.3 mm and toothed gears of module 5 made of 15CrNi6 steel, case carburized to depth 0.6 mm were analyzed. Quenching intensity of nitrogen and helium was compared and its influence on microstructure, dimensional changes and wheels geometry was assessed. Helium is proposed as an alternative cooling medium because of its higher quenching power in comparison to nitrogen. Better mechanical properties of the core of case hardened elements were achieved in case of helium quenching. No negative effect of helium cooling medium on surface layer microstructures and level of distortions was observed. (C) 2012 Elsevier B.V. All rights reserved.