Роль противосварочного покрытия в трехслойных гофрированных конструкциях из титановых сплавов

Abstract

In the manufacture of three-layer corrugated structures made of titanium alloys by diffusion bonding followed by superplastic forming, stop-off materials are used. The use of stop-off material makes it possible to selectively connect sheet blanks with each other and, as a result, get a hollow structure with an internal set of stiffeners in the form of a corrugation. The effect of stop-off materials based on boron nitride and yttrium oxide on the structure and mechanical properties of the titanium alloy Ti-6Al-4V is studied. Special attention is paid to the influence of stop-off materials on the quality of solid-phase joints in a corrugated structure. It is shown that the stop-off material based on yttrium oxide leads to the least degradation of the mechanical properties of the titanium alloy. It is established that the quality of the design depends not only on the composition of the stop-off materials, but also on the procedure of its processing before diffusion bonding of blanks. The composition of stop-off materials as binders includes organic components that contain light elements: nitrogen, carbon, oxygen and hydrogen. The latter are known to be harmful impurities for titanium and its alloys, and their chemical interaction with titanium is sharply intensified at high temperatures. The traditional temperatures of diffusion bonding and superplastic forming of the Ti-6Al-4V alloy are in the range of 900 – 950°C. Therefore, it is necessary to control and prevent the process of adsorption of hydrogen, nitrogen, oxygen and carbon atoms on the connected surfaces of titanium blanks, since this can have a noticeable effect on the quality of diffusion joints, will lead to defects, and the fatigue strength of the entire structure already depends on this.