Effect of Annealing in an Active Boron-Containing Medium on Surface Hardening of Nitrided Titanium

We studied the effect of the structural and phase state of surface layers of nitrided VT1-0 titanium on its surface hardening after additional saturation in an active boron-containing atmosphere (900°C, 5 h, 0.1 MPa Ar, a mixture of boron carbide and borax). Additional treatment almost doubles the surface microhardness of the specimens. Surface hardening is a result of both the formation of borides and carbides and the introduction of additional elements into the lattice of titanium nitrides. We established that the formation of a nonstoichiometric nitride with a deficiency of the nonmetallic component prior to additional treatment enables one to reach the maximum effect of surface hardening.     

Effect of saturation parameters on the interaction of titanium alloys with carbon-nitrogen-containing media

We study some specific features of phase formation and gas saturation in the course of chemical and thermal treatment of VT1-0, OT4, and VT14 titanium alloys in carbon-nitrogen-containing (graphite and nitrogen under atmospheric pressure) and nitrogen-containing (molecular nitrogen under atmospheric pressure) media. Saturation was carried out at 750–1100°C, and the time of isothermal holding was 5 or 20 h. We have shown that, irrespective of the composition of the saturating medium, within the range 750–1000°C, the phase composition of coatings is identical and consists of TiN and Ti₂N nitrides. The quantitative proportions between them depend on the temperature and time of treatment. Owing to the specific features of the composition of a carbon-nitrogen-containing medium, the depth of the diffusion sublayer increases, and the stoichiometry of cubic nitride decreases, which leads to an increase in the surface microhardness of nitride coatings. Carbonitride coatings are formed only at high saturation temperature (1100°C). Their maximum hardness is 2.5 GPa higher than that of nitrides formed under similar conditions.Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 3, pp. 81–87, May–June, 2004.     

Modeling the process of redistribution of alloying elements in titanium alloys in interaction with gas media

Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 3, pp. 55–58, May–June, 1988.     

Corrosion resistance of titanium with diffusion carboxide coatings

Corrosion and electrochemical properties of diffusion coatings on titanium formed by saturating from the carbon-oxygen-containing medium in aqueous 80% sulfuric acid solutions are studied. It is found that morphology of diffusion coatings affects the protective properties of titanium. It is shown that in extra-corrosive sulfuric-acid media carboxide coatings provide titanium with high protective properties, which exceed the corrosion resistance of carbide and oxide coatings. Original Russian Text ? S.V. Guryn, I.N. Pogrelyuk, V.N. Fedirko, I.V. Dyug, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 3, pp. 306–311.     

Effect of strain textures on the high-temperature interaction of titanium with rarefied gases

We studied the influence of the type and degree of perfection of the original crystallographic strain texture of thin-sheet semifinished products of VT1-0 alloy on the processes of high-temperature interaction with rarefied oxygen-containing gases. It is shown that the basic texture facilitates the process of increase in the concentration of interstitial impurities in subsurface layers of the metal, intensifies the process of nucleation of oxide phases, and accelerates the process of formation and growth of oxide films. The “prismatic” texture is characterized by the intensification of diffusion (gas saturation and sublimation) which manifests itself in an increase in the depth of the zone of solid-solution hardening as well as in the growth of the surface roughness of the metal caused by the development of sublimation micropatterns. The indicated effects become more pronounced as the crystallographic strain texture becomes more perfect. We determine the constants of phase-boundary reactions and estimate the ratios of diffusion coefficients of interstitial impurities for various crystallographic textures. This enables one to take into account the influence of the strain texture on the conditions of mass exchange through the metal-gas boundary as well as the conditions of mass transfer in the titanium matrix and, therefore, to develop a model of the diffusion saturation of titanium alloys in gases. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 32, No. 5, pp. 28–36, September–October, 1996.     

Effects of nitriding on titanium alloy strength and plasticity

Summary Studies have been made on the effects of temperature and time on nitriding and from the pressure of the nitrogen on the strength and plasticity of pseudo- and + titanium alloys. Factors are observed that provide for retaining a high level of mechanical characteristics.Karpenko Physicomechanics Institute, Ukrainian Academy of Sciences, L'vov. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 1, pp. 81–84, January–February, 1993.     

Interaction between amorphous boron and titanium alloys in a gaseous oxygen-containing medium

We study the influence of oxygen partial pressure in the course of diffusion saturation of titanium with the formation of boride phases (TiB, TiB₂) at 900°C. We establish the dependence of the reactivity of saturating medium, consisting of powdered amorphous boron and a vacuum atmosphere, on the oxygen partial pressure. We also present some physical characteristics of boride coatings. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 5, pp. 30–34, September–October, 2006.