Spray forming and post processing of superalloy rings

Abstract

Spray forming as a technology to produce near net shape components or preforms for additional forming operations with defined microstructural properties is well known for several alloys and applications. The production of spray formed superalloy rings made of IN718 and U720 for aero engine components in order to reduce production cost is the goal of the current EU-research project. Several spray runs were carried out at University of Bremen to optimize the process parameters regarding a low porosity, low segregation and a high yield. Macro and micro-etchings were prepared to analyze the influence of the parameter variations on before mentioned structural properties. Several optimized rings were used to examine the influence of thermomechanical processing on porosity and microstructure of spray formed superalloy rings. Hot isostatic pressing and forging processes were performed separately as well as in combination in order to obtain the ideal post processing route, which was determined via microstructure analysis. As a result of this project, it became clear that HIPping is an integral part of the post-processing of as-sprayed material, due to the fact that it was not possible to produce as-sprayed material without porosity. The development of micro- and macro structural properties through all these processes and their variations will be shown. Another paper presented here will focus on the final properties and applications of this material.