Structure of Commercial Titanium Subjected to Low-Temperature Ion Nitriding

Abstract

The structural-phase state of commercial titanium of grades ВТ1-00 (VT1-00) and ВТ1-0 (VT1-0) has been studied in the initial state and after various types of low-temperature ion nitriding. In the initial state, the VT1-00 and VT1-0 alloys have a single-phase α-Ti structure with a hexagonal close-packed crystal lattice. The hardness of titanium is 140–150 HV 10. It has been shown that ion-beam nitriding of VT1-00 alloy at low temperatures of 350 and 450 °С leads to the formation of thin (up to 5 μm) nitrogen-hardened layers with a hardness of 160–180 HV 0.05. As a result of ion implantation at temperatures of 500 and 550 °C, a nitrogen-modified layer with a microhardness of 190–220 HV 0.05 is formed in the surface layers of the VT1-00 titanium alloy, containing a solid solution of nitrogen in the α-Ti matrix phase. Nitrogen implantation of the VT1-00 alloy at a temperature of 620 °C leads to the formation of titanium nitrides TiN0.26, ε-Ti2N, η-Ti3N2-x in the surface layer of titanium alloy. The microhardness of VT1-00 titanium treated with nitrogen ions at 620 °C increases to 360 HV 0.05. In the case of ion-plasma nitriding (IPN) of VT1-0 titanium at 550 °C for 5 h, a nitrogen-modified layer up to 20 μm deep is recorded in its surface layer, containing isomorphic phases: α-Ti and titanium nitride TiN0.26. The microhardness of the VT1-0 titanium alloy subjected to IPN is 190 HV 0.01.

Keywords

• commercial titanium
• ion-beam nitriding
• ion-plasma nitriding
• modified layer
• solid solution
• titanium nitrides
• microhardness