A COMPLEX THERMAL-CHEMICAL TREATMENT INFLUENCE TO CORROSION RESISTANCE OF STEEL PRODUCTS

CUJOGE

Abstract

The article examines the effect of complex chemical-thermal treatment (CTT) of steel products, including cementation, diffusion saturation with chromium and quenching on the corrosion resistance of steel products in a 30% aqueous solution of HCl and 3% NaCl. St3, 40X, 40X13, 20X13 steels were used as processed materials. It was found that the CTT allows to obtain coatings with a thickness of 7 to 27 microns, while the microhardness of the coated samples surface reached 24,000 MPa, depended on the temperature of the CTT. It was found that the rate of corrosion is affected by the elemental composition of the material, CTT modes, the composition of the corrosive medium. The testing of samples revealed that uncoated steels have lower corrosion resistance than materials subjected to CTT. At the same time, the corrosion rate of materials decreased in proportion to the increase in the chromium content in and the decrease in the carbon content in the coated material. The corrosion rate was reduced most effectively in the NaCl environment. Thus, the corrosion rate of samples made of St3 steel decreased by 11.6 times, from 40X steel by 8.22 times, 40X13 by 4.56 times, 20X13 by 4.1 times. In a 30% aqueous HCl solution, the corrosion rate of samples made of St3 steel decreased by 4.6 times, from 40X steel by 4.4 times, 40X13 by 3.99 times, 20X13 by 3.84 times. Also, it was found that the corrosion resistance is influenced by the temperature of the CTT. Thus, at a temperature of 1000°C, the corrosion rate in 3 % NaCl was 0.08 g/(m2* hour). With an increase in temperature to 1070°C, the corrosion rate decreased to 0.059 g/(m2*hour). Similarly, the temperature of the CTT affected other materials under study.