AISI 4340 nitride 1

[mfgenggear]

Please advise or give a link to data
need info on what case hardness can be obtain with 4340 steel at the surface.

did google searches & came up blank.

Kind Regards

Mfgenggear

 

[TVP]

Table 1 in this Gear Technology article shows a summary for several gear materials:

http://www.ewp.rpi.edu/hartford/~ernesto/F2010/EP1/Materials4Students/Quinn/Wolf2003.pdf

Figure 3 in this Gear Technology articles shows some data for a similar European Cr-Mo alloy:

http://www.ctd.uni-lj.si/publications/bojan/GT_3 (2003).pdf

Table 6.3 on page 136 of Rakhit's book "Heat Treatment of Gears" shows a typical surface hardness after nitriding of 4340 to be 85.5 HR15N minimum.

 

[mfgenggear]

Thank You TVP

Mfgenggear

 

[blacksmith37]

The nitride layer is typically very thin so hardness testing is problematic, even a 15N Rockwell may be too deep, (hardness will typically > 90 15N, if the case is not penetrated). Small loads with Knoop or DPH/ Vickers are generally required.

 

[mfgenggear]

blacksmith37

Thank you for your reply.

Have you process parts that where able to obtain 90 15N Surface Hardness?

if so What type of Nitride process used. Gas, Ion , or Salt Bath?


Thanks Again

Mfgenggear

 

[tbuelna]

mfgenggear,

AMS 2759/6 gives a minimum surface hardness of 85.5 HR15N for gas nitrided 4340.

Superficial hardness of 90 HR15N is roughly equivalent to Rc 60.

The nitrided case (after white layer removal) would typically be .010 to .015 inch deep, and depth is mostly dependent upon time in the furnace. Depths up to about .030" can be achieved in some materials. Core hardness will be a result of the nitriding temperature used.

While the nitrided case surface hardness is quite high, the case hardness falls off quite quickly below the surface. For example, if you have 90 HR15N right at the surface, at .010" below the surface you might only have 80 HR15N. Thus, if your are performing a finish grind operation on a nitrided surface, you must be very careful about controlling stock removal.

Hope that helps.
Terry

 

[arunmrao]

Please refer to the book by my good friend David Pye "Practical Nitriding and Ferritic Nitrocarburizing". You might also want to contact him on his web site .

_____________________________________
"The richer we have become materially, the poorer we have become morally and spiritually." Martin Luther King Jr

 

[mfgenggear]

Terry arunmrao

Thanks You for your reply.
what I was after is what case hardness can be obtain of 4340
on the surface. I am familiar with case depth & procedures.

Kind Regards

Mfgenggear

 

[tbuelna]

mfgenggear,

I gave you the min superficial hardness limit specified for gas nitrided 4340 per AMS 2759/6, which is 85.5 HR15N. The max hardness would likely be around 87 HR15N.

You may get better results with an ion nitriding process.

If you can substitute materials, you can get results more to your liking with nitriding alloys such as nitralloy N. Nitralloy N will get you a gas nitrided surface hardness of 90-92 HR15N.

Hope that helps.
Terry