The effects of microstructure and microtexture generated during solidification on deformation micromechanism in IN713C nickel-based superalloy

G. Liu, J. Salvat Cantó, S. Winwood, K. Rhodes, S. Birosca*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

Nickel-based superalloy IN713C produced through investment casting route is widely used for turbocharger turbine wheels in the automotive industry. The produced microstructure and microtexture are not homogeneous across the turbine component due to geometrical factors and localised cooling rate during the casting process, which give rise to inhomogeneous deformation during service. In the present paper, two kinds of in-house fatigue tests, Low Cycle Fatigue (LCF) and High Cycle Fatigue (HCF), were conducted at 600 °C in attempt to simulate the actual fatigue conditions experienced by turbine wheels in turbocharger. From Geometrically Necessary Dislocation (GND) distributions and strain analyses, it is concluded that microstructure heterogeneity such as carbide precipitates distribution within dendritic structure network determine the failure micromechanics during LCF tests. In the early stage of LCF loading, crack principally initiated within near surface carbides that have been oxidised during high temperature exposure. The higher GND density at the tip of carbide precipitates due to oxidation volume expansion are found to facilitate easy cracks initiation and propagation. Moreover, the cluster-like carbides network and its distribution can accelerate oxidation process and crack growth effectively. Furthermore, in the later stage of crack propagation during LCF, the weak interdendrite areas rotate to accommodate increased strain leading to faster cracks propagation and hence final catastrophic failure. Serial section technique for 3-D visualisation was employed to investigate the crystallographic grain orientation correlation with fracture mechanics during HCF loading. It appears that the microtexure and grain orientations are more critical than the alloy microstructure in an area with a relatively uniform carbides distribution and weak dendrite structure where HCF failure occurred. Based on the slip trace analysis, it was found that most faceting occurred in Goss grains (<110>//LD) and on slip system with the highest Schmid factor. It is concluded that cracks were initiated on planes with high Schmid factors and assisted by the presence of porosity.

Original languageEnglish
Pages (from-to)391-406
Number of pages16
JournalActa Materialia
Volume148
Early online date16 Feb 2018
DOIs
Publication statusPublished - 15 Apr 2018

Keywords

  • Fatigue crack
  • GND
  • IN713C
  • Microtexture
  • Oxidised carbides

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