Laser metal deposition of Ti-6Al-4V alloy with beam oscillation

摘要

One of the most prevalent problems of additive technologies is the improvement of process efficiency at the expense of increase in mass deposition rate and reduction of postprocessing time. Deposition rate can be improved by the modification of the shape and size of the molten pool through the optimization of laser beam power distribution. Time and cost of postprocessing depend on the surface roughness requirements and presence of macroscopic waviness. Beam oscillation can help to solve this problem. Laser metal deposition with linear beam oscillation was studied. Effects of numerous process parameters on pool shape and size was analysed by simulation. The heat conduction problem was solved analytically by Green's function method. Temperature fields due to moving normally distributed strip heat sources were studied. It was established that on increasing the oscillation amplitude up to laser beam radius the heat flux of normally distributed strip heat source decrease rapidly to 53%. Greater the beam radius, the less effect of amplitude on the peak value of molten pool width and lower allowable oscillation amplitude. Microscopic examination revealed that beam oscillation promotes obtaining smooth wall surface without any macroscopic waviness.