The effect of titanium interlayer on the mechanical and structural properties of steel- tungsten diffusion bonding

In this study the diffusion bonding of steel– tungsten using a pure titanium interlayer was investigated. Samples were heated in a special fixture under 5 MPa pressure and at the different times and temperatures in the argon furnace. The images of optical and scanning electron microscopes indicated that a detectable diffused region was formed at the Ti- W, while no detectable diffused region was formed at the Steel- Ti interface. Also with increasing the time and or temperature of the process, the thickness of diffused region was increased. Results of the energy dispersive x- ray spectroscopy (EDX) approved the diffusion of Ti and W and little diffusion of steel and Ti. The results of x- ray diffraction (XRD) approved the presence of FeTi and Fe2Ti phases at the welded region. The results of microhardness indicated that the maximum hardness is related to the 1000T1H sample and spatially in its steel- Ti interface. This maximum hardness was due to the presence of intermetallic compounds (FeTi and Fe2Ti). Regarding to the results of shear test, 950T1H had the maximum shear strength and with increasing the time and temperature of welding, the strength was decreased due to the more intermetallic formation. Regarding all the results, temperature of 900 C and time of 1 hr, were found the optimum time and temperature for steel- tungsten diffusion bonding.