Design of new oxide and hardmetal feedstock material compositions for surface technologies

Most of the feedstock materials (oxides, hardmetals, etc.) applied for thermal spraying were emperically developed and are used for decades. Many reasons exist for modification and improvement of these compositions, such as improved technical requirements, shortage and supply risks for some elements, health protection and ecological requirements.

The trial-and-error approach of the development of new and alternative materials through experimental feedstock powders is cost-intensive, ineffective, and laborious requiring a special particle fraction with good processability and sufficient amounts. Therefore, a reliable pre-evaluation method for the development of new compositions is required. An approach consisting of the preparation of sintering bodies via classical powder metallurgical processing steps, applicable for ceramics and hardmetals, is considered as an appropriate tool for such an evaluation. Such sintered bulk bodies have small sizes and allows to study interactions in complex systems, sinterability for fast densification, target properties, such as hardness, corrosion resistance in a state close to equilibria, etc. This enables extensive screening of promising compositions from complex systems, such as Al₂O₃-Cr₂O₃-TiO₂, MgO-Al₂O₃, WC-Cr₃C₂-Ni(Co) presented in this short overview. This concept also supports the interpretation of the processes during spraying and the resulting coating microstructure. Some limitations of this approach are critically discussed as well.