Laser Surface Strengthening of Heat-Resistant Titanium Alloy for Gas Turbine Engines

The structural-phase state of the surface layers of the heat-resistant twophase titanium alloy VT-8 after laser treatment in different gaseous environments is studied by the XRD and metallographic analyses. It is found out that laser melting in the atmospheres of argon, nitrogen and air leads to structural changes in the surface layers, which leads to their microhardness increase. It is shown that during laser treatment in an argon atmosphere a complete polymorphic 13- alpha '-transformation by the martensitic mechanism occurs, which together with the raising in the degree of structure dispersion leads to an increase in microhardness values from 2.99 GPa to 5.62 GPa. During laser melting in nitrogen and air atmospheres, the change in the microhardness of the treated surfaces is due to the complex influence of several factors: increasing the degree of dispersion of the structure, formation of high-strength cubic titanium nitrides of TiN type and formation of supersaturated solid solutions of nitrogen and oxygen in alpha-titanium lattice. These factors cause an increase in the microhardness of the surface layers of the laser melting zone to 7.82 GPa (in a nitrogen atmosphere) and 6.56 GPa (in an air atmosphere).