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I'll look into those curves Ed. MagBen, the sample was evaluated prior to heat treatment and looked clean - no notable carbides nor the grain boundary sigma. There was a fair bit of carbides after heat treating, in other regions of the cross-section.

I should have further explained. I had a sample lying around that I wanted to see if I could force sigma, so I threw the sample in with another heat treatment (carbon steel). That said, I do somewhat regularly talk to clients that insist that they need to PWHT austenitic SS parts. I try to talk...

Thanks for the reply MagBen. This sample was PWHT at 620°C for 2 hours, so right at the bottom end of potential sigma formation.

Sorry, I don't quite get the design issue (my own ignorance, or I don't follow what you've described), but in terms of welding and losing strength - you are going to likely gain strength in the chromoly shaft you use, at the expense of ductility. PWHT is done to temper/soften/stress relieve the...

What is the shell? 310 as well? Is your design temperature up to 1000F? or a ways below it. You could be in the sensitization range, in which case the 308L won't be as resistant to sensitization as the 310.

Anyone with experience looking at sigma phase able to give an opinion on whether or not this is it starting at the grain boundaries? Midwall of a 0.5" thick plate; around the edge of the HAZ. Etched with 20% oxalic for about 20 seconds at 5V. 250X magnification. I'm wondering about the "growths"...

Thanks for the thoughts. I've got an OK to do an EDS analysis, but it might take a couple weeks. I'll try to remember to get back on here with the results.

I agree. They have very fast cooling rates on their first layer and don't precipitate any primary carbides. But it is the same wire composition for both layers. I was given another sample to look at today from a different manufacturer. I don't have the chemistry yet, but assume it is still in...

Good suggestion. I'll look into an option for a size criteria in the software.

This is getting to the root of my question Ed. Our image analysis (via software counting pixels in a two tone image) cannot differentiate this "phase" from M7C3s. A typical image analysis count is 30 - 45% "white" and I estimate that this ordered phase accounts for up to 10% of that white count...

Thanks MagBen, I've attached another photo (still 100X mag) of the interface between the first and second layer. The ordered phase appears to grow in size as you move from the interface to the surface. This growth is what leads me to think that it may be primary M7C3 (or another composition?). I...

Chromium carbide welded with mechanized FCAW. I don't have the welding parameters, but it is an an as-welded production test, so no service. Chemistry of the deposit is around 30% Cr and 5% C.

I tried to attach two micro photos, but I think only one is being attached. There is no scale bar, but it is taken at 100X magnification with Vilella's etchant. This micro is taken at the mid-thickness of the second layer of a CCO. I've circled two regions in yellow that I am curious about. I am...

Thanks for the thoughts. Tempering temperature was around 1300F, as you assumed Ed. The finished material was 6" diameter bar stock. When I said manufacturer I should have maybe said "mill".

Thanks Ed, I looked through about 10 MTRs that I had handy and noticed the second heat treatment on two. The one I'm interested in is 84/107 ksi (yield/UTS) actual values. I also noticed it had a relatively high vanadium value of 0.012%, which I would expect to require a longer temper.

Could someone explain to me why "stress relieving" is sometimes performed after quench and tempering by the manufacturer? The material in question is 4130. I've noticed that sometimes the MTRs state a stress relief at slightly lower temperature, but similar time to the temper temperature and...

Thanks mrfailure. I agree the discussion took a turn, which was my own doing. I realize that the 4130 discussion was not related to the GS-18NiMoCr3. The GS-18NiMoCr3 is being used as a support structure and I'm fairly confident it is cast. My question was where I could find a specification...

Thanks again Ed. That confirmed what I kind of thought was the case. I definitely see MTRs on a somewhat regular basis that only specify AISI 4130.

What about forged round bars with MTRs that only specify AISI 4130? There must exist some sort of specification for AISI 4130, but I cannot find it. My dealings with AISI 4130 is through welding procedures and in that case, I typically specify UNS G41300 for the chemistry, but it bugs me that I...

Thanks Ed. Is there an explanation for this? I'm asking out of ignorance, but it seems some materials have standard chemistries, but no specification. For example, AISI 4130 - I cannot find a specification for this, but I have no doubt that the countless manufacturers of it are following the...