Hardening method for existing 4340 forged part

[dharhay]

We made solid threaded shaft(200mm dia)with groove in one end out of 4340 forged. That groove holds up a several ton load. The load bearing land of the groove has been etched with LM51 to help hold grease on its surface. Also, there are radii on the grooves to lessen the stress intensification.

We now want to make the load bearing surface of the groove a little harder than the 33 Rc that is now and harden only the portion of the threaded shaft that is grooved.

Please suggest some hardening methods that can be done with the thought of minimizing distortion and hardening the surface to a minimal depth to around 40-45 Rc.

Thanks.

Dave Harhay
Bronx, Taylor-Wilson
North Canton, OH

 

[metengr]

I would look at induction hardening considering the hardenability of this material and carbon content.

What material is mated to this load bearing surface surface?

 

[TVP]

Harder for what purpose? Increase wear resistance? Increase resistance to pitting or other surface degradation due to high contact stress in the groove? Or increase strength (shear, tensile, etc.)? If it is one of the first two, then salt bath nitriding (local immersion of the shaft) may be a possibility. If it is the latter, probably only induction hardening and tempering will be sufficient. Shot peening or roller burnishing (hard rolling) may also be possibilities if increased fatigue strength (resistance to alternating stresses) is desired.

 

[dharhay]

Thanks for the replies. I have been away from the office, but want to say thanks for the answers.

Dave Harhay
Bronx, Taylor-Wilson
North Canton, OH

 

[swall]

In addition to induction hardening, you might want to look at flame hardening, as it sounds like this is a one off part.