Modelling of the laser surface nitriding of Ti-6Al-4V alloy - analysis of heat transfer and residual stresses

A three-dimensional finite element modelling of the laser surface nitriding of Ti-6Al-4V alloy is presented. Design capabilities of ANSYS parametric d esign language (APDL) were employed for this purpose. The model calculates transient temperature profiles, the dimensions of fusion zone and residual stresses in the laser surface nitrided Ti-6Al-4V alloy. Model simulations a re compared with experimental results, acquired on-line using an ultra-high -speed shutter camera which is able to acquire well-contrasted images of th e molten pool, and off-line using metallographical and X-ray diffraction an alyses which show very good agreement. The results are further discussed to provide directions for reducing the residual stresses, as well as for feed back and process control.