Interstitial Hardening of the Surface of Titanium Alloys by Vacuum Heat Treatment

We have determined the kinetic parameters of interaction of VT1-0, VT5, OT4-1, and VT16 alloys with a rarefied gaseous medium. We have established the interrelation between the parameters of chemical heat treatment (T, τ, and p, the interstitial hardening of surface layers of the metal, and its phase and structural state. The conditions of saturation (T, τ, and p) being equal, hardened layers differing in the microhardness and thickness of the layer H and l are formed on titanium alloys of different structural classes. Single-phase VT1-0 and VT5 α-titanium alloys as well as OT4-1 pseudo-α-alloy are the most sensitive to the conditions of gas saturation: the hardness and its gradient in the hardened layer grow significantly. As the β-phase content increases (VT16), changes in the parameters of chemical heat treatment affect less the hardness of the surface layer, but the depth of the hardened zone grows with temperature T and time τ. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 2, pp. 63–70, March–April, 2005.     

Features of diffusion dissolution of oxide films on titanium under conditions of thermocycling

We theoretically and experimentally investigate isothermal and thermocycling dissolution of oxide films on titanium in vacuum. The important role of accumulation of damages in the process of dissolution under thermocycling is underscored. For example, thermocycling can favor an increase in the size of a gas saturated layer with a decrease in the concentration gradient. We use a variation in the thickness of oxide layers under thermocycling in vacuum for the calculation of the constantsn andn ₁. The constants are employed for physicomathematical model of interaction of titanium with an oxygen-containing medium to determine the influence of thermocycling. Kapenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 34, No. 1, pp. 78–82, January–February, 1998.     

Endurance of VT1-0 Titanium Alloy Subjected to Solid-Solution Surface Hardening

We study the influence of solid-solution hardening (by the method of thermal-diffusion saturation from a rarefied oxygen-containing atmosphere) of the surface layers of VT1-0 titanium alloy on its fatigue resistance in bending with rotation. It is shown that the dependence of fatigue limit on the degree of surface hardening has a maximum whose value depends on the depth of the hardened zone. We managed to increase the original fatigue limit of the alloy by 38% for a relative increment of the surface hardness K of 70% and a depth of the hardened zone l of 30 μm. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 3, pp. 119–122, May–June, 2005.