Destructive check in which a production part or witness coupon is sectioned, ground, polished and etched, usually in nital, so the case shows as a dark band and decarb, cracks or soft zones become visible. A quick macro etch gives a visual case depth on the floor; the full lab version adds a microhardness traverse and a microstructure review.
Grab one gear off the top tray for a cut and etch before you release the rest.
Also heard as
- section and etch
- cut-up
- met check
Related terms
Nital etch
An etch of nitric acid in alcohol that reveals steel microstructure and grinding damage.
Case depth
Thickness of a hardened surface layer, measured from the surface to a specified hardness or structure.
Microhardness
Hardness measured with very small loads under a microscope, used for thin cases and individual phases.
Decarburization
Loss of carbon from the surface of steel during heating, leaving a soft skin that will not fully harden.