Extending the Use of Nitriding Processes to Reduce Distortions and Fuel Consumption

In order to meet requirements for lower fuel consumption, low friction powertrain-components are needed. Nitriding and nitrocarburising are thermochemical heat treatment processes that enhance the surface properties, e.g. high resistance to adhesive and abrasive wear as well as low friction and high corrosion resistance, of steel components. Beside this, another benefit is low distortions of the heat treated components due to the low process temperature.

To take a better use of the benefits provided by nitriding processes, and to replace case carburizing which is more commonly used today, a better knowledge and understanding of the properties that are possible to achieve by the different nitriding processes, in combination to selection of steel, is needed. A major challenge for many components is how to obtain required strength properties, e.g high-strength fatigue properties, as can be achieved by case carburising.

In this work the influences on compound layer, diffusion zone and residual stresses have been evaluated for different steel grades after nitriding and nitrocarburizing. Distortions on gear wheels have been evaluated for different combinations of steel and nitriding process compared to case carburized wheels. This will be followed by fatigue testing.