High-temperature oxidation of intermetallics formed by group IV transition metals with chromium

We have studied the oxidation resistance of chromium intermetallics: TiCr₂, HfCr₂, and ZrCr₂, in the temperature interval 873–1473 K with isothermal holding of the specimens for up to 20 h. We have shown that the intermetallics TiCr₂ and HfCr₂ are oxidized 2–3 times more slowly than pure titanium and hafnium, but more than 1–2 orders of magnitude faster than chromium at T≤1273 K and 4–6 times faster at 1473 K. In this temperature interval, the intermetallic ZrCr₂ is rapidly oxidized at an increasing rate as the heating temperature rises. The scaling resistance of intermetallics of Group IV d metals with chromium is determined by formation of scales in which the major role is played by the oxides TiO₂, HfO₂, and ZrO₂, with weak protective properties.     

Distinctive features of corrosion damage to low-alloy chromium subjected to high-temperature salt corrosion

We study the influence of alloying elements (La, V, Al, Si) on the mechanism of interaction of chromium with NaCl and Na₂SO₄ salt melts at a temperature of 900°C. Alloying elements form chemically stable scales with enhanced adhesive properties and reduce the rate of salt corrosion largely due to a decrease in the share of grain-boundary damage.Institute of Problems in Materials Science, Ukrainian Academy of Sciences, Kiev. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 31, No. 2, pp. 103–108, March – April, 1995.     

High-Temperature Strength of Titanium Alloys Alloyed with Silicon,Aluminum, and Zirconium in Air

We study the behavior of VT1-0 titanium alloy alloyed with silicon, aluminum, and zirconium in the process of oxidation in air at 800°C for 30 h. It is shown that, as a result of alloying of the alloy with silicon up to 6 wt.%, its high-temperature strength becomes more than two times higher. This effect is connected with the influence of silicon on the diffusion processes in the metal and scale and changes in the morphology of scale. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 2, pp. 83–88, March–April, 2005.     

Specific features of the oxidation of complex titanium alloys in the as-cast and recrystallized states

We study the heat resistance of complex titanium alloys with 4.5–11 wt.% Al in the as-cast and recrystallized states at a temperature of 800°C for 50 h. It is shown that the procedure of alloying has the same influence on the as-cast and recrystallized metals, and the initial structure affects the kinetics of oxidation of the latter. In this case, the ground recrystallized structure promotes the formation of oxide films with high adhesive strength guaranteeing high levels of the heat resistance of the alloy for long periods of holding. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 3, pp. 112–117, May–June, 2008.     

Evaluation of the Heat Resistance of Low-Alloy Chromium Alloys by the Parametric Method

We construct the parametric heat-resistance diagrams for low-alloy VKh-2K and VKh1-17A chromium alloys recommended for the production of units operating at high temperatures. These diagrams allow one to determine the increment in the weight of alloys at temperatures of oxidation of 1000–1400°C and holding of up to 1000 h and can be used as a bank of experimental data.     

A Parametric Method of Determining the Heat Resistance of BX-2K and BX1-17A Chromium Alloys

Based on temperature-time tests on the heat resistance carried out for temperatures in a range of 1273–1673 K and for exposures from 10 to 1000 h, the parametric diagrams of heat resistance are plotted in the logq vs. pframe of reference for low-alloyed chromium alloys BX-2K and BX1-17A. These diagrams allow the heat resistance at different temperatures and exposures not only to be assessed but also to be predicted without any tests for temperatures at least 100 K higher and exposures 5–10-times longer than those mentioned above. These diagrams can be used as the data bank of experimental results.     

High-temperature oxidation of intermetallics formed by group IV transition metals with chromium

We have studied the oxidation resistance of chromium intermetallics: TiCr₂, HfCr₂, and ZrCr₂ , in the temperature interval 873–1473 K with isothermal holding of the specimens for up to 20 h. We have shown that the intermetallics TiCr₂ and HfCr₂ are oxidized 2–3 times more slowly than pure titanium and hafnium, but more than 1–2 orders of magnitude faster than chromium at T1273 K and 4–6 times faster at 1473 K. In this temperature interval, the intermetallic ZrCr₂ is rapidly oxidized at an increasing rate as the heating temperature rises. The scaling resistance of intermetallics of Group IV d metals with chromium is determined by formation of scales in which the major role is played by the oxides TiO₂ , HfO₂ , and ZrO₂ , with weak protective properties.     

Phase formation during fabrication of chromite-containing coatings

We have studied the process of phase formation in coatings based on chromium and yttrium. The coatings were formed on chromium alloy (Cr 98. 5 %) by plasma sputtering. We studied the phase composition after formation of the coating and after heating in different environments (air, oxygen, argon, vacuum). We have determined the effect of various factors on the phase formation process in the coatings. We have established that heating the coatings led to an increase in the amount of yttrium chromite and an improvement in the structure.Institute of Problems in Materials Science, National Academy of Sciences of Ukraine, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1/2(383), pp. 73–77, January–February, 1996. Original article submitted January 25, 1994.