Carbide Precipitation in the Grain Boundries of 17-7PH
Carbide Precipitation in the Grain Boundries of 17-7PH
(OP)
Is it normal to find any carbide precipitation in the grain boundries of stainless steel type 17-7PH in the annealed or heat treated condition?





RE: Carbide Precipitation in the Grain Boundries of 17-7PH
Is this an actual part? Do you have some micros?
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Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm
RE: Carbide Precipitation in the Grain Boundries of 17-7PH
RE: Carbide Precipitation in the Grain Boundries of 17-7PH
See this thread for my difficulty:
Thread330-105178'
during that challenge I did various treatments of 17-7PH to find the highest strength heat treatment with the particular heat of material that I have.
(due to production part work that project was put on hold.)
I will be continuing the metallographic study friday, and hope to have some micrographs/EDS info available w/in two weeks.
I will post what I can (allowed to, and able to) here.
nick
RE: Carbide Precipitation in the Grain Boundries of 17-7PH
I would expect based on the information in this Handbook that depending on the solution treatment temperature, the actual carbon content, and the balance of ferrite formers (Cr, Si, Mo, Al) and austenite formers (C, Mn, Ni and N) one could have chromium carbide precipitation at ferrite stringer/austenite interfaces and possibly along grain boundaries for Condition A.
Further information on Condition A material after fabrication;
Depending on the temperature used for the austenite pre-conditioning heat treatment, the PH 17-7 will develop further chromium carbide precipitation at ferrite/austenite stringer interfaces, and possibly an intergranular network of M23C6 carbides (if the carbon content of the material is at the high end of the carbon specification). The formation of the carbides that occurs during this pre-conditioning treatment removes chromium and carbon from solution resulting in transformation to martensite at higher temperatures. As the pre-conditioning heat treatment temperature is increased to 1500 deg F, this lowers the martensite start temperature. Pre-conditioning at 1750 deg F results in fewer carbides, thus sub-cooling is necessary to achieve complete transformation to martensite.
RE: Carbide Precipitation in the Grain Boundries of 17-7PH
Most of the 17-7 that we run is light gage, rarely over 0.083". And we run toward the low C end of the range.
Some of the strip that we recive mill annealed does have singificant amounts of carbides and other cats and dogs in the structure. Since this material is rolled sheet the structure tends to have bands (like a sandwich) and not strictly following grain boundaries.
I have looked at micros of our mill annealed product (1900-1950F WQ) and there are small scattered secondary phases. No masive grain boundary pahses.
I have looked at samples that were both TH1050 and RH950. Yes, the structure of the TH material is a mess. Pimary and secondary carbides, retained austenite and phases that I don't have a clue about. Some in GB, but a lot along the prior ferrite/autenite interfaces.
The RH material is very clean by comparison. Well dispersed, uniform, fine pahses. And increadible mechanicals.
= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm
RE: Carbide Precipitation in the Grain Boundries of 17-7PH
hamid
RE: Carbide Precipitation in the Grain Boundries of 17-7PH
Hamid