Investigation of Dimensional and Shape Changes in Combined Surface Layer Heat Treatments of Gear Components Made of EN31CrMoV9 and EN42CrMo4

Abstract Surface heat treatments such as case hardening, nitriding and surface hardening are often used to improve the performance properties of gear components. Due to limitations in the individual processes, e. g., with regard to the distortion that occurs, the achievable hardening depth or surface hardness, combinations of several processes are important in order to achieve better process efficiency and component properties. The present investigations focus on dimensional and shape changes in the combination of nitriding and induction hardening on samples and gears made of the materials EN31CrMoV9 and EN42CrMo4, measured before and after the heat treatments. For the gears examined, comparable dimensional and shape changes were determined after the combination treatment as for induction hardening alone, which overall resulted in larger geometric changes than nitriding. Due to the dimensional and shape deviations of the geometric features, reworking by means of gear grinding is advisable in certain cases.