New Carbonitriding Processes

摘要

In the last centuries carbonitriding was mainly used to enhance the hardenability of unalloyed steels. IWT developed gas-carbonitriding and low-pressure-carbonitriding processes to increase fatigue behavior and quality compared to case hardening. For example, modern gas-carbonitriding processes make it possible to extend materials strength, so that the limit of use of a given alloy can be expanded. The paper shows examples for the treatment of ball bearing and case hardening steels. The treatment results in microstructures, which are unusual, compared with conventional heat treated parts. They are characterized by high amounts of retained austenite and carbonitride precipitations. By a controlled process, which has been developed in cooperation with PROCESS-ELECTRONIC, it is possible to adjust surface carbon- and nitrogen content independently. Low pressure carburized parts have the advantage that no internal oxidation occurs. So they have the potential of leading to a higher strength. Nowadays LP-carburizing is used in a wide range, whereas LP-carbonitriding processes are at a starting point. In this paper possibilities and limitations of this process are shown. So, inline controlling of LP-processes in a classical way is not possible, but simulation guided process control. The paper will give examples for LP-carbonitriding processes and the resulting microstructure.