Investigation of the effect of WAAM surfacing on the structure and coefficient of thermal linear expansion of the AK-5 alloy

The paper presents the results of studies to determine the coefficient of thermal linear expansion (CTLE) of the Sv-AK5 alloy after WAAM surfacing. The data of CTLR measurements of grown workpieces during pulsed electric arc surfacing in the temperature range of 20-400 °C are presented. The influence of heat removal conditions on the structure of surfacing zones and CTLR of grown workpieces is shown. It has been established that in the lower layers of the grown workpiece, due to accelerated heat removal into the substrate, a more dispersed structure is formed compared to the overlying layers. An increase in the dispersion of the structure of a sample cut and prepared from the lower deposited layers of the grown workpiece leads to a decrease in the growth of the CTLR when heated to 180-200 °C due to an increase in the area of the grain boundaries, which inhibits the expansion of the “body” of the grains when heated. The change in the CTLR of the alloy during heating in the range from room temperature to 400 °C was studied depending on the direction of surfacing and cutting of samples for measurements. A comparison of samples cut along the direction of surfacing and perpendicular to it showed that their CTLR values differ noticeably only in the temperature range from room temperature to 80 °C. When the temperature increases to 400 °C, the difference in the thermal expansion of all samples practically disappears, which indicates the stability of the formed structure and the absence of anisotropy in the thermal expansion of the deposited samples.