Tensile properties and microstructures of investment complex shaped casting

Abstract

The tensile properties of complex shaped nickel based superalloy casting were investigated at elevated temperature. Specimens were prepared from investment casting with/without hot isostatic pressing (HIP) treatment. Grain size and microstructure of specimen are examined through optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The results show that the tensile properties change remarkably, although the specimens were cut from the same casting; the ultimate tensile strength and elongation in semilogarithmic scale of the specimens have obvious linear relationship with grain size. The HIP treatment can not only improve the tensile properties but also increase the sensitivity of elongation in terms of grain size, which roots from the morphology and redistribution of bifilms, δ phase, Laves phase and γ″ precipitates. The present work will provide a better understanding of the local profile–property relationships of complex shaped casting in bottom filling system and suggest that the local profile should be considered seriously in design and manufacture of the complex shaped superalloy casting.

Keywords:

• Complex shaped casting
• Tensile properties
• Grain size
• Precipitates
• Bifilms

Acknowledgement

The authors gratefully acknowledge the financial support from the Science and Technology Commission of Shanghai (project no. 11521100703).