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Re: Carbide Sensitization

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Posted By<" ">Mike McGuire on May 23, 2002 at 13:55:57:

In Reply to: Carbide Sensitization posted byHJackson on May 22, 2002 at 14:49:52:

: Can anyone provide a definition of carbide sensitization?

Sensitization is the precipitation of chromium carbides ( actually mixed iron/chromium carbides)along the grain boundaries of stainless steel. This precipitation depletes the volume of metal near the grain boundaries of chromium in solution, thereby diminishing its corrosion resistance.
In austenitic stainless it occurs at a maximum rate around 1500F and more slowly down to 900F.
The rate is a complex function of a number of factors. In austenitics, it is avoided by keeping carbon below 0.03%. In ferritcs it is only avoided by combining all carbon and nitrogen with Titanium or Niobium.
Austenitics can be quenched from above 1600F, which prevents the precipitation, but ferritics cannot be quenched rapidly enough.

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Subject: Re: Re: Carbide Sensitization

Comments:: : Can anyone provide a definition of carbide sensitization? : Sensitization is the precipitation of chromium carbides ( actually mixed iron/chromium carbides)along the grain boundaries of stainless steel. This precipitation depletes the volume of metal near the grain boundaries of chromium in solution, thereby diminishing its corrosion resistance. : In austenitic stainless it occurs at a maximum rate around 1500F and more slowly down to 900F. : The rate is a complex function of a number of factors. In austenitics, it is avoided by keeping carbon below 0.03%. In ferritcs it is only avoided by combining all carbon and nitrogen with Titanium or Niobium. : Austenitics can be quenched from above 1600F, which prevents the precipitation, but ferritics cannot be quenched rapidly enough.

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