A Combinatorial Approach To Study The Phase Constitution Of The Ni-Al-Pt System

Platinum has a beneficial effect on improving alumina scale adhesion and decreasing the alpha alumina growth of aluminide bond coats in thermal barrier coatings. However, complex phases form among Ni, Al and Pt during service due to diffusion between bond coat and underlying Ni-base superalloy substrate. A combinatorial/high-throughput approach to study alloy phase equilibria with precious compositions is high-efficient and cost-saving. The microstructural evolution of a Ni-Al-Pt diffusion triple fabricated by annealing at 1100 degrees C for 96 h followed by water-cooling was characterized by transmission electron microscopy and electron probe microanalysis. The high temperature Pt3Al(h) phase is stabilized due to dissolved Ni, indicating that Ni is a stabilizer for Pt3Al(h). A ternary phase, Ni2PtAl, predicted to exist, has been observed experimentally with L1(2) structure adjacent to (Ni,Pt)(3)Al, while the L1(0)-structured tetragonal NiPt2Al phase is also confirmed in the Ni-Al-Pt system. Upon cooling, the Ni-rich beta-(Ni,Pt)Al undergoes a martensitic transformation from beta (B2) to beta'-(Ni,Pt)Al (L1(0)). The orthorhombic D-2h(19)-structured (Ni,Pt)(5)Al-3 phase with lattice parameters a = 0.747 nm, b = 0.682 nm, and c = 0.376 nm was found to form from beta'-(Ni,Pt)Al martensite. The orientation relationship of D-2h(19), and beta ' phases is (100)[010] D-2h(19) // (100)[001] beta'. (221) twins are observed in lamellar (Ni,Pt)(5)Al-3. Phase constitution is determined in the Ni-Al-Pt system at 1100 degrees C. The mechanism of formation of (Ni,Pt)(5)Al-3 from beta'-(Ni,Pt)Al was analyzed. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.