Influence of aging and HIP treatment on the structure and properties of NiAl-based turbine blades manufactured by laser powder bed fusion

Abstract

The parameters and strategy of laser powder bed fusion (LPBF) applied in the manufacture of turbine rotor blade models using an innovative Ni41Al41Cr12Co6 alloy were optimised. The effect of exposure to heat treatment by aging and hot isostatic pressing (HIP) on the evolution of structural phase transformations was studied by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR TEM). HIP eliminates the structural anisotropy and facilitates the segregation of 0.02–1.5 μm coherent α-Cr precipitates oriented along the NiAl <011> direction. Nanoparticles of the Hf and Heusler phase Ni2AlHf were predominantly redistributed from the boundaries equiaxial with the NiAl grains, which increased the elevated-temperature strength of the alloy. The mechanical properties were studied in the temperature range of 923–1273 K. The temperature-force dependence of the steady-state creep rate, activation energy for creep, and mechanisms of plastic strain accumulation were determined. The temperature dependences of the Young's modulus and offset yield stress were plotted. It was found that the post-treatment of the aged LPBF- built blades by HIP had a positive influence on the resistance to plastic deformation. The high-temperature strength of the rotor blade material fabricated by LPBF + aging + HIP was higher than that of the as-HIP and as-LPBF + aging material by 85 K. The temperature-force operating conditions (over 100,000 h) at a plastic strain less than 1 % were identified.