Bond strength of gold alloys laser welded to cobalt-chromium alloy

Mechanical and interfacial characterization of laser welded Co-Cr alloy with different joint configurations

PURPOSE

The mechanical and interfacial characterization of laser welded Co-Cr alloy with two different joint designs.

MATERIALS AND METHODS

Dumbbell cast specimens (n=30) were divided into 3 groups (R, I, K, n=10). Group R consisted of intact specimens, group I of specimens sectioned with a straight cut, and group K of specimens with a 45° bevel made at the one welding edge. The microstructure and the elemental distributions of alloy and welding regions were examined by an SEM/EDX analysis and then specimens were loaded in tension up to fracture. The tensile strength (TS) and elongation (ε) were determined and statistically compared among groups employing 1-way ANOVA, SNK multiple comparison test (α=.05) and Weibull analysis where Weibull modulus m and characteristic strength σ_ο were identified. Fractured surfaces were imaged by a SEM.

RESULTS

SEM/EDX analysis showed that cast alloy consists of two phases with differences in mean atomic number contrast, while no mean atomic number was identified for welded regions. EDX analysis revealed an increased Cr and Mo content at the alloy-joint interface. All mechanical properties of group I (TS, ε, m and σ_ο) were found inferior to R while group K showed intermediated values without significant differences to R and I, apart from elongation with group R. The fractured surfaces of all groups showed extensive dendritic pattern although with a finer structure in the case of welded groups.

CONCLUSION

The K shape joint configuration should be preferred over the I, as it demonstrates improved mechanical strength and survival probability.