Effects of trace Sn and Cr addition on microstructure and mechanical properties of TC17 titanium alloy repaired by wire arc additive manufacturing

Wire arc additive manufacturing (WAAM) provides an efficient and low-cost potential for repairing blades or blisk made of titanium alloy. In this work, three deposition samples were fabricated by pulse arc WAAM for the test of microstructure and mechanical properties with Sn and Cr addition. Results show that the epitaxial growth beta columnar grains traversing several deposition layers were formed with the addition of 2 wt% Sn. Large elongated beta columnar grains were inhibited with the addition of Cr particles, and several equiaxed grains were formed due to constitutional supercooling of Cr and thermal supercooling of pulse arc. With the addition of 2 wt% Sn and 4 wt% Cr, the size of primary alpha phases were remarkably refined with the length no more than 2 mu m and the width no more than 0.1 mu m. The fracture position changed from the deposition zone to the base metal (Far-heat affected zone) with the addition of 2 wt% Sn and 4 wt% Cr compared to the other two depositions. It is of great guiding significance to the repair of TC17 blades or blisk by AM method. Meanwhile, the forming mechanism of two types of microstructure within the weak zone (Far-heat affected zone) and the fracture mechanism were discussed in detail. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study utilized pulse arc WAAM to fabricate deposition samples with added Sn and Cr, showing that the addition of Sn results in the formation of β columnar grains, while the addition of Cr inhibits the growth of large β columnar grains and forms equiaxed grains. The size of primary α phases can be remarkably refined by the addition of Sn and Cr, changing the fracture position. The research has important guiding significance for the repair of TC17 blades or blisk.