Posted by Dirk Feil on June 27, 2010 at 15:32:41:
Normally a Hcl (60-75%), HNO3 (2.5-4%), FeCl (21-37.5%) solution will etch .0002"-.0004" from the surface of machined 304L. As observed on IN718 though, it appears when depth of cuts are shallow, and there is more pushing that cutting, the resultant disturbed/abused/cold-worked surface tends to pit, rather than etc. Any rationale for this? In metallography similar events are observed, and appear related to surface strain, but have not read an exhaustive explaination as to why, and most importantly, how to limit by specification of the machining practice.