TiAl alloy and 42CrMo steel were vacuum brazed at temperature of 1 143-1 213 K for 120 s-1 500 s. The microstructure was analyzed using optical microscope,scanning electron microscope( SEM) and energy dispersive spectrometer( EDS). The thickness of the reaction layers was measured using an analysis software. The hardness of the reaction layers and phases was tested and compared using nano-indenter and traditional microhardness tester. In order to determine the weak phases or layers,the brazed joints were te...