Modification of Ti-6Al-4V titanium alloy surface relief by compression plasma flows impact

Abstract

Investigation of compression plasma flows impact on surface relief of Ti-6Al-4V titanium alloy was carried out in this work. Profilometry, X-ray diffraction, scanning electron microscopy and samples weight measurements were used as investigation techniques. The findings showed that plasma impact led to the formation of developed surface relief (Ra parameter was changed in the range of 0.7-2.7 µm) due to the action of hydrodynamic instabilities at the melt-plasma border. Increase in the number of pulses resulted in the growth of Ra value. Numerical simulation of surface evolution under plasma impact was carried out on the basis of the model of incompressible fluid potential flow. Simulation data correlated with experimental data set. The hydrodynamic flow of the melt during plasma impact led to another process - surface erosion. Increase in both the absorbed energy density and the number of pulses resulted in erosion intensity increase. Formation of titanium nitride on the surface was observed as a result of the interaction of nitrogen (as a plasma generating gas) with the surface heated under plasma impact. Titanium nitride film prevented the development of the surface relief formed by the action of hydrodynamic instabilities.