Influence on liquid quenching in heat treatment by means of previous surface structuring

• Applicant: Professor Dr.-Ing. Olaf Keßler
• Subject Area: Metallurgical, Thermal and Thermomechanical Treatment of Materials
• Term: from 2013 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 240635062

During the first project stage, the feasibility of influencing on liquid quenching by selective surface structuring has been proven. Successful surface structures of metal components have been derived.Increasing the heat transferring surface area has been found to be an important mechanism. Thereof new strategies for surface structuring result. Up to now, deep surface structures have been intended, whose tips should penetrate the vapour layer during liquid quenching. In the second project stage, the focus shall be on smoother surface structures with large heat transferring surface areas. This will also ease integration of surface structuring in component manufacturing, because smaller material allowances can be used.Real components cannot exhibit highly rounded edges, to reduce the superimposed influence of sharp edges on liquid quenching. But often, real components exhibit slightly rounded or bevelled edges. It shall be investigated, to which extent edges must be rounded or bevelled, to allow an effective surface structuring for liquid quenching.Surface structuring can accelerate rewetting during liquid quenching, but also hinder rewetting, especially if surface structures are horizontal, i.e. perpendicular to the rewetting direction. Therefore the orientation of surface structures shall be investigated as an additional parameter. The focus shall be on structures parallel to the rewetting direction.The feasibility of influencing on liquid quenching by selective surface structuring has been shown for cylinders. Particular advantages of surface structuring are expected for components with varying cross sections. In thick cross sections, quenching can be accelerated, whereas in thin cross sections, quenching can be slowed down by surface structuring. This would result in more homogeneous quenching and thereby lower residual stresses and lower component distortion.Surface structuring of steel has been successful, but surface structuring of aluminium alloys has been not that successful. Instead, selective anodic oxidation is a promising process, which shall be investigated for aluminium alloys.

• DFG Programme: Research Grants