Mechanical properties of laser welded joints in dissimilar alloys

Objectives: (i) To evaluate some properties of the welded joints between Cobalt-Chromium and Titanium. (ii) To investigate the feasibility of laser welding between fusing joint of dissimilar alloys. Materials and Method: Thirty specimens of (1×3×42) mm were prepared as recommended by ISO. Specimens were divided into experimental groups (15 Cobalt-Chromium and 15 Titanium) and one control group of 26 specimens of Cobalt-Chromium. Each specimen was invested and moulded into mould rings with a special investment material. After that all specimens were casted. Each specimen was then cleaned utilizing Acetone solution. All specimens of Titanium were then checked by using X-ray to ensure that all specimens are porosity free. Specimens of each alloy were then laser welled. Tensile strength, three-point bending test and modulus of elasticity were evaluated. Two specimens were selected randomly for SEM examination to investigate the topography of the specimen under laser welding. Data were then statistically analyzed using t-test. Results: For tensile strength, the average maximum stress was significantly reduced for laser welding specimens as compared to the control specimens (p = 0.000). For 3-Point Bending test, the experimental groups were significant difference compared to control (p = 0.000). However for modulus of elasticity, there were no significant difference between tested groups (p = 0.254). SEM shows some porosity inside laser welding joints. Conclusion: The results shows that 3-points bending test and tensile strength for experimental group was significantly reduced than control group. However, there were no significant differences between both groups for modulus of elasticity.