Ok I got a story for you. About 25 years ago I needed a Mega block repaired that had a small window and pan rail damaged.
I was told to go see Charlie in Middletown, NY. He was an older guy who did repairs on all kinds of engines and machinery.
He prepped the block and “cold welded” half inch at a time with nickel rods. He then ground smooth , dressed and stress relieved it with a hammer and punches...When he was finished you couldn’t see the repair.
The story was that in his youth he designed and built the machine that polished the lens/mirror on the Hubble telescope for NASA.