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

Highlights: • Large elongated β columnar grains were inhibited with the addition of Cr particles. • The size of primary α phases was remarkably refined. • The fracture position changed to the far-heat affected zone. -- Abstract: 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 β columnar grains traversing several deposition layers were formed with the addition of 2 wt% Sn. Large elongated β 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 α phases were remarkably refined with the length no more than 2 µm and the width no more than 0.1 µm. 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.