INFLUENCE HEATING RATE AND PROCESSING TIME ON THE KINETICS OF A ZIRCONIUM ALLOY THERMODIFFUSION SATURATION BY OXYGEN

2018;
: 103-113
Authors:
1
Karpenko Physico-Mechanical Institute of the NAS of Ukraine

Aim. Study of the kinetics of oxidation of zirconium alloy Zr-1% Nb and Zr with heating in air, depending on the heating rate and processing time. Method. Zirconium alloy Zr-1% Nb and zirconium of vacuum remelting were chosen as the material of the studies. For the thermal treatment, a laboratory electric furnace SNOL30/1300 was used. The heating rate was varied from 2.5°C/min. up to 20°С/min., and cooled together with the furnace. When the samples were cooled to a temperature of 270°C, air was introduced into the chamber of the furnace for a thin oxide film, which prevents the metal from being irrigated at atmospheric conditions. The samples were thoroughly washed in acetone and alcohol before heat treatment, and then dried. Results. It was found that during the oxidation in air, an increase in the heating rate from 2.5°C/min. up to 6.0 and 7.5°C/min. reduces the activation energy of the oxidation process of Zr from 70.2 to 67.0; 52.7 kJ/mol, respectively. Whereas for Zr-1% Nb zirconium alloy, the heating rate increases from 5°C / min. to 10; 20°C/min. causes an increase in the activation energy of the oxidation process of the zirconium alloy Zr-1% Nb from 65 kJ/mol to 70.1; 78.5 kJ/mol, respectively. Scientific novelty. The kinetics of oxidation of the Zr-1% Nb and Zr zirconium alloy was experimentally studied and analytically described for heating in air, depending on the heating rate and residence time. It is shown that an increase in the rate of Zr zirconium heating of vacuum remelting Zr from 2.5 to 7.5°С/min, and Zr-1% Nb alloy from 5 to 20°С/min leads to a decrease in the size of the ZrO2 oxide film. It was found that an increase in the temperature from 750°C to 800°C for 5 hours leads to a change in the oxidation function from parabolic to quasilinear. Practical significance. The regularities of saturation of zirconium alloys have been established. They can be used to select the processing regimes for finished articles from zirconium-based alloys.

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