Selective chemical milling of recast surfaces

Details Selective chemical milling of recast surfaces Selective chemical milling of recast surfaces

1982-01-11

1983-10-25

Powell, William A.

Adhesive bonding and miscellaneous chemical manufacture

Delaminating processes adapted for specified product

Delaminating in preparation for post processing recycling step

156628, 156630, 156634, 156643, 156656, 156664, 219121EK, 219121LJ, 252 792, C23F 100, B23K 900, C09K 1304

Patent

active

044117302

ABSTRACT:
Disclosed is a process for machining nickel-base superalloys wherein a thermal-effect process, such as laser or electric discharge machining, is first used to remove material but leaves a recast layer. Next a chemical milling process is used wherein the etchant only attacks and removes the recast layer. The etchant is comprised by volume percent of 40-60 HNO.sub.3, 5-20 HCl, and balance H.sub.2 O, with which is included 0.008-0.025 moles/liter FeCl.sub.3 and at least 0.016 moles/liter CuSO.sub.4. The FeCl.sub.3 improves removal rate but tends to cause unwanted pitting and intergranular attack. These tendencies are inhibited by the addition of CuSO.sub.4 ; preferably the molar ratio of CuSO.sub.4 to FeCl.sub.3 is 2:1. The beneficial combination of FeCl.sub.3 and CuSO.sub.4 is usable in other etchants.

REFERENCES:
patent: 3866398 (1975-02-01), Vernon et al.
patent: 4239954 (1980-12-01), Howard et al.
patent: 4353780 (1982-10-01), Fishter et al.

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