Abstract: Objective: To investigate the influence of welding gap distances on the mechanical properties and fatigue life of Co-Cr alloy laser-welded joints. Methods: Dumbbell rods made of Co-Cr alloy were laser-welded with the gap distances of 0.00mm, 0.25mm and 0.50mm respectively (n=10). The non-weld group was chosen as control group. All specimens were subjected to three-point bending test on the material testing machine. The maximum compressive stress values and fatigue life were recorded automatically. The fracture of specimen was tested with microscopic phase analysis. Results: The maximum compressive stress values and fatigue life of laser-welded groups were smaller than the non-weld group (P<0.05). No statistically significant difference of the maximum compressive stress values was found within the laser-welded groups. The longest fatigue life was found in the 0.25mm group (P<0.05), and no statistically significant difference was found between 0.00mm group and 0.50mm group. Conclusion: Proper gap distance (0.25mm) is good for enhancing the fatigue life of Co-Cr alloy laser-welded joints.

Key words: Laser-welding, Cobalt-chromium alloy, Fatigue life