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TVP, that is just the sort of info I was looking for. Thank you!

Ed - The plan is to limit depth to under .003". The question is more one of magnitudes. There is relatively little information out there (at least that I have found) related to fnc and thin walled parts. But that is basically a guess as to where to start testing. It may be that .005" would be...

I know your parts are out of your direct control, but we have had good luck using normalized rather than annealed for the raw stock when the part is particularly sensitive to distortion. Also, you might consider having the parts machined there and the heat treatment done here where you can...

metengr - Thank you for the info! We have used FNC in the past (with good success) to improve wear and corrosion resistance on some smaller 4340 parts. Someone did not really think through how thin walled the parts were in this case, before the suggestion was made. I appreciate the reference.

Corrected Version Not Typed on a Smartphone Keyboard. :) Hello, we are planning on gas nitrocarburizing some short sections of thin walled (< 0.020”) 4340 tubing. The question has come up that since we are going to get basically through penetration with the nitrocarburizing, what is that going...

Hello, we planning on gas nitrocarburizing some short sections of thin walled (< 0.020”) 4340 tubing. The question has come up that since we are going to get basically through penetration with the nitrocarburizing, what is that going to do to the impact strength of the tubing? My guess it that...

Thank you for the reply. I do understand there are other options with electroplating. I was specifically wondering about mechanically plated parts. The application I was thinking about was mechanically plated flat springs of extremely high tensile steel. They are not electroplated because of...

Corrosion protection. I am hearing the trivalents aren't preforming as well for tin /zinc mixtures.

Could anyone suggest an alternative topcoat for a mechanical tin / zink plating? Most of the suppliers I have contacted about trivalent chromate have said they aren't recommending them for tin / zinc mixtures.

I understand about the risks from electroplating. The question has been with chromate on mechanical plated parts. With mechanical plating the surface layer is more porous and I am guessing there is where the debate was stemming from.

Hello, I have received a bit of conflicting advice about a chromate conversion coating applied over mechanically plated parts. One source says there is hydrogen embrittlement risk, the other say there is no concern. I would be interested in any additional opinions or information. Thanks!

Thank you everyone who replied. The wire thickness issue makes a lot of sense. Also the greater tolerance for surface treatments. I also hadn't properly considered the issue of sag as an independent from a fatigue fracture. With suspension springs you have a lot of geometry to play with...

TVP - First let me thank you for that wealth of information. I suspect I might have a misunderstanding. I looked through the Handbook of spring design published by SMI and I noticed that fatigue resistance seemed to be a direct function of tensile strength. I then came across the statement...

Forgive the amateurish question, but could someone tell me why automotive suspension springs are generally silicon steels? It seems to me that higher tensile steels would increase fatigue life. My only guess was that heat build up in the spring required a more heat tolerant material? I would...

I know this is way late... but did you look into nitriding?

Thanks for the suggestion salmon2. I was hoping to find a reference that might have charts or the like where you could look up 1095 steel at various hardness and it would give approximate changes from either annealed or normalized condition or both. Ideally, one that would have a wide range of...

Hello, I am hoping to get some suggestions for a consolidated reference on dimensional changes (volume changes) in various metals / alloys as a result of heat treating. Preferably I am looking for one that gives curves or at least data points contrasted with hardness. Any suggestions or...

unclesyd - I read through the articles posted and while they are very informative those don't really address the thing that is tripping me up. I know that active stainless is more anodic than passive stainless, but I don't really get why, which is where my confusion appears to be rooted. My...

Just to be clear. I do understand that passive in the chart does not literally mean 'passivated.' I am just assuming that passivated stainless is passive at least until the oxide layer is breached.

edstainless - Actually I am specifically talking about the impact of passivated versus non-passivated stainless on other materials. Somehow I must be stating my confusion poorly or misusing terms. Let me try this another way... If we go with this chart...