Creep Properties Dependence to Solution Heat Treatment of Second and Third Generation Ni-Based Single Crystal Superalloys

Computational design is increasingly being used by industry and research institutes for the development of new compositions of Ni-based single crystal (SX) super-alloys. Alloy selection is often based on the mechanical properties of the fully heat-treated Ni-based SX superalloys. However, a more complex chemical composition leads to a more complex solution heat treatment (ST). The development of a ST to reach optimum homogenization, requires time and resources, overall penalizing the time/cost savings provided by computational design approaches. Thus, the present study investigates several superalloys "as cast" mechanical properties to predict the creep life of the solution heat treated alloy. Four commercial superalloys with distinct chemical composition were chosen. Each alloy was investigated in (i) the as cast (AC) and (ii) solution treated and aged (ST) states. The superalloys were creep tested at 950 degrees C/390 MPa and 1050 degrees C/190 MPa. A creep life improvement by a factor of 1.5-3 times has been observed after the ST, irrespective of the alloy chemical composition or creep test conditions. Down-selecting alloys' composition from the as-cast creep properties can be a viable approach to speed-up alloy design.