Effect of joining temperature on the microstructure and strength of W-steel HIP joints with Ti/Cu composite interlayer

Cylinders of tungsten and P91 steel are successfully joined by using a hot isostatic pressing (HIP) method with the help of the combination of Ti and Cu as interlayer. The effect of joining temperature on the interfacial microstructure and tensile strength of the joints are investigated in this work. No intermetallic compound was observed at W/Ti and Cu/steel interfaces of the joints bonded at the temperature studied. However, the electron probe microanalysis and X-ray diffraction analysis reveal that Ti2Cu, TiCu, Ti3Cu4 and TiCu4 formed at Ti/Cu interface of the joint bonded at and below 950 °C. Further increase of the joining temperature caused the significant reduction in the intermetallic compounds at the Ti/Cu interface, and at 1050 °C the intermetallic compounds totally disappeared after joining due to the effect of liquid formation at Ti/Cu interface. The results indicate that the Ti/Cu liquid forming interlayer can be used to improve joint strength.