Continental O-470 Nitriding process?

[Cubswede]

This might be posted in the wrong forum section, but anyway..

I have a Experimental class 108-3 with a o-470-K wide rod crank where the previous owner had it ground down to the 0,01". Unfortunately they did not Nitride it afterwards as per the overhaul manual. I would like to Nitride it here in Sweden, but I would need to know the exact process to use. There are a couple of Nitriding processes, (Gas or ION etc) and I want to use the correct one. Does anyone have any insight in this?
Br/Henrik

 

[MartyC]

The attached article has a nice explanation of the nitriding process.

Nitriding Explained - How It Works, Benefits & Types | Fractory

Nitriding is a type of case-hardening process that hardens the outer layer of a part by adding nitrogen to its surface.

fractory.com

 

[Cubswede]

The attached article has a nice explanation of the nitriding process.

Nitriding Explained - How It Works, Benefits & Types | Fractory

Nitriding is a type of case-hardening process that hardens the outer layer of a part by adding nitrogen to its surface.

fractory.com

Thanks Marty,
I know there are different processes and how they work, I just want to make sure I use the correct process on my crankshaft. I would believe the common gas nitriding process is used, but I do not know what exact gas composition, time and temperature is used since this is not explained in the overhaul manual. I doubt I will get an answer from Continental if I would ask them? I did ask Aircraft specialties services, and hopefully I will get some feedback from them.
The simplest way would be to send my crank to USA and have it nitrided, but the shipping only is $2000.....

 

[MartyC]

Ouch!!! Seems $2000 is a bit much.

I believe the gas nitriding is the best choice since it's a proven process and been around for a long time. I am surprised there isn't an aerospace heat treating facility somewhere near you with nitriding capability.

Anyway, here is another article describing the gas nitriding process, basically a dissociated ammonia gas atmosphere at an elevated temperature. According to this article, it looks like the temperatures range 925F to 975F for single stage and possibly up to 1025F to 1050F for the second stage.

https://supersystems.com/wp-content/uploads/T4601-1-R1-May2009.pdf

I hope this helps.

MartyC

 

[Cubswede]

Ouch!!! Seems $2000 is a bit much.

I believe the gas nitriding is the best choice since it's a proven process and been around for a long time. I am surprised there isn't an aerospace heat treating facility somewhere near you with nitriding capability.

Anyway, here is another article describing the gas nitriding process, basically a dissociated ammonia gas atmosphere at an elevated temperature. According to this article, it looks like the temperatures range 925F to 975F for single stage and possibly up to 1025F to 1050F for the second stage.

https://supersystems.com/wp-content/uploads/T4601-1-R1-May2009.pdf

I hope this helps.

MartyC

Thanks again Marty,
I got answer from Aircraft specialties services, and they confirm that they use the gas nitriding process, but could not give more details because it is proprietary information. Understandable . I had contact today with a company about 3 hours from where I live that do both Ion and gas Nitriding as their everyday business. They wanted to know the crankshaft alloy to be able to suggest the best methode to use. I did search today but could not find any info on the crank material. But from my memory i think I have read somewhere that the crank should be AISI 4340 steel.
Anyone who know?

 

[MartyC]

I can look into it later in a couple of days. My guess is a 4XXX series steel; you are probably right thinking a 4130. Best to be sure…

You could ask if they could confirm with a non-destructive method to determine the alloy.

 

[180Marty]

This outfit might be able to help with what metal the crank is made of. They do cryogenic treatment on aircraft parts.

 

[MartyC]

I found this report about the Lycoming crankshaft failures from early 2000's. It is very well written report. The team did a really detailed investigation of the failures. Plus, there is a wealth of information about crankshaft manufacturing, including some information on the nitriding process.

Per this report, the Lycoming crankshafts are made from AMS 6414, which is Vacuum Arc Remelt (VAR) SAE 4340. It may be a stretch, but my guess is the Continental crankshafts are probably made from the same material.

Here is the report:

 

[MartyC]

Here is another article about crankshafts.

Crankshaft Design, Materials, Loads and Manufacturing, by EPI Inc. (epi-eng.com)

 

[Cubswede]

Here is another article about crankshafts.

Crankshaft Design, Materials, Loads and Manufacturing, by EPI Inc. (epi-eng.com)

Marty,
Thank you very much for taking your time digging up those two very interesting documents! I found something similar about crankshaft failures on Continentals, but the full document was only for purchase.
I will read thru what you posted. Great reading

 

[Cubswede]

This outfit might be able to help with what metal the crank is made of. They do cryogenic treatment on aircraft parts.View attachment 108237

Thanks Marty,
I will check it up

 

[MartyC]

You're most welcome, Cubswede. I enjoyed looking them up and reading them.