Manufacturing Process of a Forged TiAl Turbine Rotor Containing B2 Phase

Abstract

Manufacturing process of a forged TiAl alloy with a commercial size is investigated in order to realize practicalapplication of TiAl as a turbine rotor material in a high performance and high efficiency turbine engine. Accomplishment of apparently contradicting properties such as good hot deformability and high temperature strength is pursued in a alloy of Ti-45Al-8Nb-2Cr (at%) which contain B2 phase. The phase transformation behavior of this alloy is first investigated during quenching from temperatures between 1473K1673K and the basic scheme for the manufacturing process, e.g. casting→heat treatment in the (γ+B2) phase field→isothermal forging→heat treatment in the phase field which contains α₂ (α) phase, is defined. Then various factors such as the heat treatment and forging conditions for the stages up to the isothermal forging are examined by compression tests. Finally, it is shown that manufacturing of a 210mm in diameter 40mm in thickness forged piece can be successfully done using a industrial 6000ton press without causing any plastic deformation of the IN100, die material.