Selective chemical milling of recast surfaces
US4411730A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 11, 1982 |
| Grant date | Oct 25, 1983 |
| Priority date | — |
| Expiry date | Jan 11, 2002 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC23F1/28
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.