Experience in the application of the non-destructive method of acoustic emission in the production of titanium billets and products of transport engineering

The article discusses the issue of using the non-destructive method of acoustic emission at the stage of blank production. So, due to the violation of the heat treatment modes, various defects are formed in the starting material, which affects the operational properties of the finished products. To eliminate this problem, the stages of production of titanium blanks and products of transport engineering were studied, such as: heat and mechanical treatment, ultrasonic quality control, determination of the level of mechanical properties and control of the structure. In the course of the research, a method of acoustic emission control was developed and tested. The experiment on setting the locations of defects was carried out on ingots of VT22 titanium alloy during cooling. The reliability of the developed method is confirmed by the existing method of ultrasonic flaw detection. It has been established that this method can be effectively used to control workpieces and machined workpieces for the manufacture of particularly critical mirrors for searching for inhomogeneous inclusions and increasing the efficiency of the technological process by eliminating machining of VT1-0 titanium surfaces with inhomogeneous inclusions. In addition, this method can be used to search for defects commensurate with the grain size of the ingot, as well as significantly smaller sizes.

Influence of surface hardening by combined thermal force impacts on VT22 titanium alloy fatigue life and damage

The study covers the influence of electromechanical surface treatment (EMT), non-abrasive ultrasonic finishing (NAUF), their complex influence with subsequent aging on the fatigue life and surface microhardness changes. Samples for research were made of VT22 transition alloy rods after standard thermomechanical treatment. EMT was carried out by sample surface rolling with a roller and applying a high density current between them. As a result, surface thermomechanical treatment was carried out with the local fast surface heating and cooling. NAUF were implemented by shock treatment with an ultrasonic emitter striking on the treated surface. This revealed 1.8 times higher fatigue life when loading by rotational bending (with amplitude of 0.5σв) for samples after NAUF in comparison with the untreated initial state together with a slight increase in microhardness (up to 16 %). EMT reduces microhardness and fatigue life by almost 20 % and 70 %, respectively. EMT + NAUF complex processing has an insignificant effect on microhardness, but it increases fatigue life by 40 % with respect to EMT. Aging at 450 °C for 5 hours increases microhardness after EMT by 30–40 % with a simultaneous increase in fatigue life by 2 times. The aging of samples subjected to EMT + NAUF revealed virtually no increase in microhardness, but increased fatigue life by almost 3 times (as compared to EMT). According to fractography results, the reduction in fatigue life after EMT is associated with a reduction in the crack initiation stage, which virtually excludes this stage of fatigue damage accumulation from the overall sample fatigue life.