I may be welding an 8620 pinion gear to an 8620 shaft soon. Both pieces have had carburizing, and heat treatments, and case hardening done to them. Does anyone have any suggestions on filler rod/ pre-heat or PWHT temps if necessary for this welding procedure? I have been researching all week, and many suggested 400 F for pre-heat, with slow post weld cooling. Rods suggested so far have included 312 SS, and Eutectic 680S. I've also been told that this may have had a oil quench, and thus does not require a pre-heat/post heat process. I'm hoping to find out more on the heat treatments next week, but any advice in the meantime would be greatly appreciated. The application will be a temporary part to be used until a full billet part is produced. It is strictly for testing purposes right now. I plan on GTAW process, using ARgon shield, and grinding the case hardening off.
Definately do the pre & post heat treating, 400f minimum. You won't get the strength of a billet part, but perhaps enough for the testing. We used 9018 [stick] for tool steel repairs, then covered that with a tool steel rod for wear resistance. If You are only joining and don't need wear resistance don't overlay with tool steel, it is rather brittle, not really strong. Undermatching the filler metal helps with cracking. We didn't use 8620, so I cant offer first hand advice.
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