Effect of residual stress on the strength of an alumina–steel joint by partial transient liquid phase (PTLP) brazing

The effect of residual stress on the strength of joints made between alumina and stainless using partial transient liquid phase (PTLP) brazing with the Ni of an 80Ni20Cr core interlayer was studied. It was found that the residual stress caused by the thermal expansion mismatch between alumina (Al2O3) and stainless steel-304 (SS304) deteriorated the Al2O3–SS304 joints severely compared to Al2O3–Al2O3 joints with the same brazing parameters. The high residual stress zones obtained through finite element method (FEM) simulation corresponded well to the fractographic observation of the Al2O3–SS304 joints. FEM simulation also demonstrated that Ni and Ni–Cr filler metals are compliant layers that are suitable to relieve thermal residual stress in the Al2O3–SS304 joints.