Laser weldability of Zr-2.5Nb alloy to AISI 410 stainless steel with Ni filler

The nickel interlayer improved the laser weldability of Zr-2.5Nb to AISI 410 stainless steel. The fusion zone contained a large amount of refined and tough dendritic γ-Ni(Fe, Cr) solid solution (182 ∼ 268 HV), while the brittle Zr(Fe, Cr)2 intermetallic compound (1171 ∼ 1460 HV), which was the main phase as the result of direct welding of Zr-2.5Nb to SS410 as well as the source responsible for the welding cracks, disappeared. Only limited quantities of Zr2(Ni, Fe), Zr7Ni10 (and/or Zr2Ni7) intermetallics were present mainly in the form of thin layers (less than 200 μm thick in total) near the fusion interface with Zr-2.5Nb. Those Zr-Ni based intermetallics showed relatively higher toughness and lower hardness (301 ∼ 497 HV) than the brittle Zr(Fe, Cr)2, which reduced the overall cracking sensitivity of the laser-weld.