Multilayer SiBCN/TiAlSiCN and AlOx/TiAlSiCN coatings with high thermal stability
Nowadays, there is a growing interest in the development of tools working in dry metal processing to meet the increasingly greater demands for environmental protection by eliminating environmentally harmful liquid lubricants and coolants. Dry metal processing can lead to working temperature on the tool surface exceeding 1000 °C. We developed multilayer TiAlSiCN/SiBCN and TiAlSiCN/AlOx coatings as a promising candidate working in high speed dry metal processing. The coatings were deposited by magnetron sputtering of TiAlSiCN target and ion sputtering of either SiBC or Al2O3 targets. To investigate thermal stability, samples were annealed in vacuum at 1000, 1300, 1400°C for 1 h. The results demonstrated that after vacuum annealing at 1300°C, the TiAlSiCN/AlOx coatings lost multilayer structure due to recrystallization, which was accompanied by a significant grain growth, Si loss, and h-AlN precipitation. In contrast, the TiAlSiCN/SiBCN samples annealed at 1300°C completely preserved their multilayer structure. After 1400°C, recrystallization of the TiAlSiCN/SiBCN coating was only observed to occur in several upper layers, whereas other part of the coating retained its initial microstructure. Hardness of the TiAlSiCN/SiBCN and TiAlSiCN/AlOx coatings increased from 34 and 24 GPa to 40 and 30 GPa at 1000°C and then decreased to 27 and 15 GPa at 1300°C, respectively.