Investigation of the phase formation in magnetron sputtered hard multicomponent (HfNbTiVZr)C coatings

Abstract

Multicomponent carbides have gained interest especially for ultra-high temperature applications, due to their ceramic hardness, good oxidation resistance and enhanced strength. In this study the phase formation, stability and mechanical properties of (HfNbTiVZr)C multicomponent carbide coatings were investigated. Phase stability was predicted by the CALPHAD (CALculation of PHAse Diagrams) methods. This revealed that the multicomponent solid solution phase is only stable at elevated temperatures, namely above 2400 °C. At lower temperatures a phase mixture was predicted, with a particular tendency for V to segregate. Magnetron sputtered thin films deposited at 300 °C exhibited a single NaCl-type multicomponent carbide phase, which attributes to the kinetic stabilisation of simple structures during thin film growth. Films deposited at 700 °C, or exposed to UHV annealing at 1000 °C, however, revealed the decomposition of the single-phase multicomponent carbide by partial elemental segregation and formation of additional phases. Thus, confirming the CALPHAD predictions. These results underscore the importance of explicitly considering temperature when discussing the stability of multicomponent carbide materials, as well as the applicability of CALPHAD methods for predicting phase formation and driving forces in these materials. The latter being crucial for designing materials, such as carbides, that are used in applications at elevated temperatures.

Keywords

• High entropy ceramics
• Multi-principal element carbide
• Multicomponent carbide
• Physical vapour deposition (PVD)
• CALPHAD