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The Effect of Bainite Volume Fraction and Morphology on the Wear Resistance of a Ferrite-Bainite Dual phase Steel

Safarpour, Masoud | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52992 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Ekrami, Ali Akbar
  7. Abstract:
  8. The studied steel was AISI 4340 steel. In order to obtain dual-phase steel with a volume fraction of 60, 66 and 75% bainite, samples were heated in the α+γ region at temperatures of 730, 735 and 740 oC for 120 minutes and then to create lower and upper morphology of bainite, samples were transferred directly to salt bath at different target temperatures (300 oC and 400 oC) and kept 60 minutes. Also, to produce a Martemper microstructure, the full martensitic sample was tempered at 260 oC for 90 minutes. Tensile and hardness tests revealed that with the increasing volume fraction of lower bainite, yield strength, tensile strength, and hardness increased from 986 to 1211 MP, 1185 to 1519, and 377 to 511 HV, respectively, but elongation decreased from 14.5 to 8.8%. In upper bainite microstructure, yield strength, tensile strength, and hardness increased from 924 to 1032 Mpa, 1043 to 1190 MP, and 319 to HV 392, respectively but elongation decreased from 11.4 to 7.1%. On the other hand, the martemper microstructure has a tensile strength of 1952 MP and a yield strength of 1575 MP. Pin-on-Disk wear test results showed that the martemper microstructure in both 10 and 50 N forces has the lowest abrasion rate and surface damage. At 10 N force, in dual-phase microstructures, the wear rate decreased with the increasing the volume fraction of bainite and tensile strength, respectively. At 50 N force, the lowest wear rate is related to the bainite volume fraction of 66%, and the wear rate has increased with increasing the volume fraction of bainite to 75%
  9. Keywords:
  10. Wear Properties ; Tensile Properties ; Ferrite-Bainite Dual Phase Steels ; Bainite Morphology ; Tempered Martensite ; Bainite Volume Fraction

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