Enhanced creep resistance induced by minor Ti additions to a second generation nickel-based single crystal superalloy

Over the past decades, the evolution of high-performance nickel-based single crystal (SX) superalloys has advanced along the pathway of continuous increment in the Re content, which leads to microstructure instability, as well as increased density and cost. This paper proposes an alternative approach to enhance the creep resistance by slight composition modification instead of increasing the Re content. We system-atically investigated the effects of minor Ti additions on the microstructure, lattice misfit, and elemental partitioning behavior of a novel second generation nickel-based SX superalloy, whose creep performance exceeded that of Rene N5. The addition of 0.5 wt.% Ti resulted in more and finer gamma' precipitates, narrower gamma channels, and a higher magnitude of the gamma/gamma' lattice misfit. In addition, all partitioning coefficients of Re, Mo, W, and Cr elements in the gamma matrix were increased. Thicker gamma' and thinner gamma lamellae were formed in the raft structure. The creep stain rate decreased significantly, and the creep life extended twice that of the base alloy at 1030 degrees C and 230 MPa. The temperature capacity of the Ti-containing alloy was superior to that of some commercial second generation SX superalloys and similar to that of Rene N6. Denser dislocation networks accumulated at the gamma/gamma' interface, confirming the dislocation strengthening mechanism during the creep process. Stronger solid solution strengthening, impeded cross-slip, and more sluggish diffusion dynamics were considered to contribute to the enhanced creep resistance of the Ti-containing superalloy. (C) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

This paper proposes an alternative approach to enhance the creep resistance of nickel-based single crystal superalloys by slight composition modification instead of increasing the Re content. Experimental results show that the addition of minor Ti can increase the quantity and size of precipitates, improve lattice misfit, and enhance the partitioning behavior of the alloy. The Ti-containing alloy exhibits significantly improved creep resistance, extended creep life, and a stronger dislocation strengthening mechanism.