I have a tooling block that is about 15"x15"x 13" long welded to a 6"x8" radius die. The block is 4140 and the radius die is 4146 and both parts have been heat treated and also nitride coated giving a case of 73-76 Rc for a depth of .080". Normally we would heat the block to 500F and weld it with 4140 GTAW, then send to heat treat, but we don't have time. I want to preheat the block, weld, peen, and controlled slow cool. What risk do I have of cracking in the HAZ or the actual weld due to this very hard case.