Diffusion bonding of Al2O3-TiC composite ceramic and W18Cr4V high speed steel in vacuum

Al2O3-TiC composite ceramic and W18Cr4V high speed steel were joined by diffusion bonding with a Ti-Cu-Ti multi-interlayer in a vacuum of 10−4–10−5 Pa. The interfacial microstructures of the Al2O3-TiC/W18Cr4V joint were investigated with optical microscope and scanning electron microscopy. The elemental concentration near the diffusion interface was evaluated by electron probe microanalysis. The results indicate that an obvious transition zone was formed between Al2O3-TiC and W18Cr4V during the vacuum diffusion bonding. The elements in the transition zone are mainly Ti and Cu with a small amount of Fe. Element Ti concentrates near the two interfaces of the Al2O3-TiC/transition zone/W18Cr4V. The microhardness of the transition zone is lower than that of Al2O3-TiC and higher than that of W18Cr4V. The formation process of the transition zone consists of five stages: (i) Formation of Cu-Ti liquid phase; (ii) Full melt of Cu; (iii) Full melt of Ti; (iv) Formation of reaction layer; (v) Formation of Cu-Ti solid solution and increment of reaction layer.