Effect of composite interlayer on bonding quality of W and steel HIP joint

Tungsten (W) and Ferritic/Martensitic Steel (FMS) bonding is one of the key technologies to fabricate breeder blankets for fusion reactor. For bonding W and FMS, interlayers help to release residual stress and prevent intermetallic compound (IMC) formation. In this work, Ni/Ti/Ni, Ti/Ni, Cu/Ni and Cu were tested for joining W/FMS using Hot Isostatic Pressing (HIP) at 900 °C for 1 and 2 h with an applied pressure of 150 MPa. Compared to W/Ti/FMS joints, Ni prevents the formation of Ti-Fe brittle phase, however, TiNi, Ti2Ni, TiNi3 and Ni4W phases weaken the bonding strength. On the other hand, W/Cu/Ni/FMS interfaces are free from IMC and joints survive the Post Welding Heat Treatment (PWHT) at 1050 ℃ and 760 ℃. The highest shear strength of W/Cu/Ni/FMS reaches 185 MPa and the samples fracture plastically.