I have to make a repair [my bad] on rear out put diameter, damaged threads. I TIG'd a spot on a spare crank and the spot got hard, can't file it. Is this typical of forged cranks? While I can grind the diameter I'm afraid it will be too hard to cut the threads needed even if I use mild steel welding rod.
Did you pre- and post heat the flange? The weld cools so rapidly on that large a hunk of steel, that the weld will be extremely hard and brittle. Pre-Heating it and probably more importantly post-heat and a very slow cooldown should make it lest hard and easier to remachine. If it was surface treated, tuftride or the like, it may need a very controlled cooldown over a period of 12 or more hours to ambient.
I thought of spray welding. Went to a shop and they said the weld holds up for bearing surfaces but can't handle side loading from threads. I haven't given up, checking further. I saw some thing about 312 Tig rod and cladding,
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