Slow strain rate tensile test properties of iron-based superalloy Suh660 in hydrogen gas

Research output: Contribution to journalArticle

Abstract

To investigate dependence of strain rate of tensile test for iron-based superalloy SUH660 (A286), tensile tests were conducted for the specimens in 70 MPa hydrogen gas and air at 150°C. Nominal stress-nominal strain curve of each strain rate in 70 MPa hydrogen gas showed same behavior to maximum load via yield point in comparison with that in air, however, each elongation at breaking point in 70 MPa hydrogen was a little shorter than that in air. The values of tensile strength didn’t depend on the strain rate in 70 MPa hydrogen as well as those in air. In addition, the difference in tensile strength wasn’t observed between that in 70 MPa hydrogen gas and that in air for the strain rate. However, it’s proved that relative reduction of area in 70 MPa hydrogen to that in air was significantly affected by strain rate of tensile test. Those values were 80%, 51%, and 32% in the case of strain rate 5.0×10 −5 , 7.5×10 −6 , and 1.25×10 −6 s −1 , respectively. The morphology of fracture surface also changed from dimple to quasi-cleavage (QC), with a decrease in strain rate. Simulation of hydrogen gas diffusion from surface to inside during experiment showed that the hydrogen diffusion layer of specimen with QC fracture surface (RRA 51%, strain rate 7.5×10 −6 s −1 ) was only 0.25 mm in depth. That implies that hydrogen content at crack tips is much higher than that of simulation due to hydrogen concentration by a couple of defects. That tendency seems to become stronger with a decrease in strain rate.

Original languageEnglish
Pages (from-to)359-366
Number of pages8
JournalISIJ International
Volume59
Issue number2
DOIs
Publication statusPublished - 2019 Feb 1
Externally publishedYes

Fingerprint

Superalloys
Strain rate
Hydrogen
Iron
Gases
Air
Tensile strength
Diffusion in gases
Stress-strain curves
Crack tips
Elongation
Defects

Keywords

  • A286
  • Dimple
  • Hydrogen embrittlement
  • Quasi-cleavage fracture
  • Reduction of area
  • Relative reduction of area
  • Slow strain rate tensile test
  • SUH660

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

Cite this

Slow strain rate tensile test properties of iron-based superalloy Suh660 in hydrogen gas. / Fukunaga, Akihiko.

In: ISIJ International, Vol. 59, No. 2, 01.02.2019, p. 359-366.

Research output: Contribution to journalArticle

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abstract = "To investigate dependence of strain rate of tensile test for iron-based superalloy SUH660 (A286), tensile tests were conducted for the specimens in 70 MPa hydrogen gas and air at 150°C. Nominal stress-nominal strain curve of each strain rate in 70 MPa hydrogen gas showed same behavior to maximum load via yield point in comparison with that in air, however, each elongation at breaking point in 70 MPa hydrogen was a little shorter than that in air. The values of tensile strength didn’t depend on the strain rate in 70 MPa hydrogen as well as those in air. In addition, the difference in tensile strength wasn’t observed between that in 70 MPa hydrogen gas and that in air for the strain rate. However, it’s proved that relative reduction of area in 70 MPa hydrogen to that in air was significantly affected by strain rate of tensile test. Those values were 80{\%}, 51{\%}, and 32{\%} in the case of strain rate 5.0×10 −5 , 7.5×10 −6 , and 1.25×10 −6 s −1 , respectively. The morphology of fracture surface also changed from dimple to quasi-cleavage (QC), with a decrease in strain rate. Simulation of hydrogen gas diffusion from surface to inside during experiment showed that the hydrogen diffusion layer of specimen with QC fracture surface (RRA 51{\%}, strain rate 7.5×10 −6 s −1 ) was only 0.25 mm in depth. That implies that hydrogen content at crack tips is much higher than that of simulation due to hydrogen concentration by a couple of defects. That tendency seems to become stronger with a decrease in strain rate.",
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