The influence of welding defects on the fracture mechanism of samples made of the VT-22 alloy, with the use of restorative surfacing with filler wires

Abstract

The restoration of the surface of damaged parts made of high-strength titanium alloys by the method of restorative surfacing with the use of filler wires is a quite reasonable and promising technique since its aims is to restore a partially damaged surface of parts while preserving their strength properties. However, this technique requires a significant number of static, fatigue and corrosion tests to be followed by suitable processing of the obtained results to correct or improve even the welding technology. The main purpose of the research was to study the fatigue behavior of samples with a restored surface by the method of metal surfacing. Fatigue tests were carried out on VT-22 alloy samples, the surface of which was restored by surfacing using SP-15 and VT-22 filler wires. Fractography revealed the presence of several welding defects (pores mainly) located both in the zone of the deposited metal and on its borders. These conclusions summarize the obtained research results and provide important information about the correlation between welding defects, fatigue strength, and the properties of the VT-22 alloy. The results showed that the presence of these defects is primarily related to the initiation of fatigue cracks. The size and shape of defects, as well as their location relative to the deposited layer, also affected the reduction of fatigue properties. Correcting the surfacing conditions may significantly reduce the critical size of defects and, as a result, significantly increase the residual life of restored parts. Keywords: high-strength titanium alloy VT-22, welding pores, segregation of defects, zone of thermal influence, cyclic loading.