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Microstructure Investigation of Low Temperature Carburized Precipitation Hardenable 17-4 And 13-8 Mo Stainless Steels

Baniasadi, Fazel | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 47346 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Asgari, Sirous
  7. Abstract:
  8. Recently, low temperature carburizing of stainless steels, especially austenitic stainless steels, have been considered by so many researchers. The improvement of tribological properties of which is so impressive so much so that such properties like hardness and wear resistance increase to manifold. In this research, low temperature carburizing was done on two kinds of precipitation hardenable stainless steels 17-4 and 13-8 Mo. After that, microstructural investigations were done on the carburized surfaces and in 5, 10, 20, 80, and 150 micrometer depths. Moreover, in each depth, in order to phase structure and tribological properties investigation, XRD and microhardness tests were done, respectively. It was seen that by going into depth, hardness decreases for two steels till receiving the substrate hardness. Then, the coherency of carburized layers was investigated. It was proved that with a little deformation, slip lines went beyond the interface of substrates and carburized layers. Also, it was seen that some of martensites being on the interface have been shared between the surrounded phases that means carburization was done on a part of which and was not done on the other part. After coherency investigation, thermal stability of carburized layers was investigated. With temperature increasing, hardness was decreased for two steels untill at 400C and 2h and 450C 2h heat treatments the hardness of PH SS 13-8 Mo and PH SS 17-4 decreased abruptly, respectively. These conditions are critical for these steels applications
  9. Keywords:
  10. Thermal Stability ; Low Temperature ; Microstructure ; X Ray Diffraction ; Precipitation Hardening ; Stainless Steel ; Carburizing

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