Microstructure and microindentation of Ti3SiC2 - Titanium filler brazed joints by tungsten inert gas (TIG) process

Herein we study the joining of Ti3SiC2 - a MAX phase - with a Ti filler (Ti3SiC2/Ti-filler) using a TIG-brazing process. The microstructures of the interfaces were investigated by scanning electron microscopy and energy dispersive spectrometry. When Ti3SiC2 comes into contact with the molten Ti - filler during the TIG-brazing operation, it starts decomposing into TiCx and a Si-rich liquid. Simultaneously, the molten Ti infiltrates into the Ti3SiC2 resulting in a 200 µm thick duplex region, comprised of TiCx and a Ti-rich phase with some dissolved Si. Both Si and C are found in the solidified Ti; the Si source is from the Si-rich liquid, while the presence of C indicates that some of the C diffused into the Ti. Upon cooling, C- containing Ti- rich lamellae form the solidified Ti. Microindentation results of the decomposed Ti3SiC2 layer show an increase in hardness and a decrease in elastic modulus relative to T3SiC2. Notably, no cracks were observed.