Study on cracks in laser direct-cladded titanium layer on low carbon steel

By adjusting laser power and nozzle speed in laser cladding technology, crack-free titanium layer with even thickness and titanium mass percentage over 99%, was obtained on the substrate of low carbon steel without any intermediate layer when heat input was between 12-20 J/mm. The temperature field and the mechanical strain were simulated. Together with phase diagram and EDS, it was found that an interface zone, consisted of TiFe, (TiFe+-Ti) eutectic compound and -Ti, was formed between the titanium layer and the substrate. The interface zone is brittle and cracks occur in it. In titanium layer crack also occur if the mechanical strain exceeds the critical plasticity of metal. By reducing heat input, the mechanical strain decreases, thus a crack-free titanium layer with even thickness can be obtained.