Corrosion modes in P/M ferritic stainless steels

Michael C. Baran, Barbara A. Shaw

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

The corrosion properties of powder metallurgy ferritic stainless steel alloys were investigated and compared to those of wrought 409Cb stainless steel. Anodic potentiodynamic polarization was performed on all specimens in 0.1M NaCl with a sean rate of 0.5mV/s. In general, the powder metallurgy alloys were seen to exhibit lower open circuit potentials, higher current densities, and a lower degree of possivity than their wrought counterparts. The differences in open circuit potential and current density values were attributed to a crevice corrosion mechanism within the pores of the powder metallurgy part and the formation of secondary compounds, such as chromium carbides, during sintering. Crevice corrosion within pores was also thought to degrade the passivity of the powder metallurgy alloys. Intergranular corrosion tests carried out for 24h in boiling 6w/o CuSO4+ 16w/o h2SO4 were found to be too aggressive fo all the powder metallurgy specimens. A new intergranular test in 6w/o CuSO4 + 0.5w/o H2SO4 was found to be useful in ascertaining the degree of secondary compound formation, or "sinter sensitization" in the powder metallurgy specimens. Finally, a heat treatment at 816°C(1500°F) for 2h was found to reduce the intergranular corrosion rate of the powder metallurgy 434L specimens sintered at 1290°C (2350°F) by a factor of 77.

Original languageEnglish (US)
Pages (from-to)57-68
Number of pages12
JournalInternational Journal of Powder Metallurgy (Princeton, New Jersey)
Volume36
Issue number4
StatePublished - May 1 2000

All Science Journal Classification (ASJC) codes

  • Metals and Alloys
  • Industrial and Manufacturing Engineering

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