The Use of CrNiCo-based Superalloy as Die Material in Semi-solid Processing of Steels

摘要

Semi-solid processing of aluminium and magnesium alloys has matured to become a well established manufacturing route for the production of intricate, thin-walled parts with mechanical properties as good as forged grades. This innovative forming technology, however, still remains as a major challenge in the case of steels. One major limitation in the thixoforming of steels has been the lack of suitable tool materials which could withstand the complex load profile and significantly increased forming temperatures which promote chemical interaction between forming dies and liquid steel. For industrial application to be attractive, the lifetime of the thixoforming tools has to be sufficient to ensure the cost effectiveness of this technology. Forming experiments using conventional hot working tool steel as die material have shown massive wear and plastic deformation. Several alternatives including copper alloys, titanium-zirconium-molybdenum based high temperature application alloy TZM, graphite and ceramics with and without suitable ceramic coatings have been tested with limited success. An attempt was made in the present work to investigate the applicability of CrNiCo-based superalloy dies in small scale forming tests in an effort to contribute to the development of semi-solid processing of steels.