Laser gas oxidising of Ti–6Al–4V surface: experimental and numerical investigation

Abstract

The laser gas oxidising of Ti–6Al–4V surface was studied. Confocal laser scanning microscopy techniques were used to investigate its two- and three-dimensional surface topographies. Gas flow behaviour was simulated to define the minimum O₂ concentration required for Ti–6Al–4V to self-sustain combustion. To understand the flow behaviour of the Ti–6Al–4V fluid, a high-speed camera monitored the evolution of the Ti–6Al–4V fluid, and the flow behaviour was simulated. Experimental and simulation results show that Ti–6Al–4V can self-sustain combustion with a high O₂ to Ar gas flow ratio, and the oxidising layer is rough with macroscopic cracks, while a low O₂ to Ar gas flow ratio results in a smooth oxidising layer without cracks. Ti–6Al–4V can self-sustain combustion when the O₂ concentration exceeds 65%. Furthermore, the laser molten pool and self-sustaining combustion zone mix and flow together, and a large self-sustaining combustion zone leads to a low convection velocity.