Study on microstructure and mechanical properties of TiC-TiB ₂ composite coatings on Al matrix by self-propagating high-temperature synthesis

The powders of Ti, C, B₄C, and polytetrafluoroethylene (PTFE) were used as the raw materials in this paper. The TiC-TiB₂ composite coatings were in-situ synthesized on the surface of ZL205A alloys by reactive cladding technology, combining with self-propagating high-temperature synthesis (SHS) and vacuum-expendable pattern casting technology. The effect of solution temperature on the microstructure, hardness, and thermal stability of Al matrix and TiC-TiB₂ coatings were investigated. The results show that, the adiabatic temperature of Ti-C-B₄C-PTFE system is much higher than 1800 K, the SHS reaction can be ignited by the vacuum-expendable pattern casting technology of molten ZL205A alloys, resulting in the formation of TiC-TiB₂ composite coatings on the surface of Al matrix. The TiC-TiB₂ composite coatings after solution heat treatment show the excellent thermal stability, the hardness of the composite coatings is HB 285, and the mass loss of composite coatings is 49.7 mg at 20 N loading, decreasing by 90%, which indicates that the wear resistance of ZL205A alloys is significantly improved.