Nondestructive Testing Method Applicability
Nital Etch, also known as Surface Temper Etch and Temper Etch, is a nondestructive test. Its purpose is to determine if overheating has occurred in a part (after final heat treat) by abusive machining or grinding that will adversely affect the required properties of the part. Specifically, it is used to look for:
- Localized Re-tempering
- Localized discontinuous carburization
- Decarburized surface layer
Etching will detect surface variations such that softer tempered materials will darken (burn) faster than harder areas.
MTC Nital Etch Laboratory Inspection Service
At Metals Testing Company, we have a complete in-house capability of equipment, chemicals, procedures, qualified personnel, waste treatment, environmental related permits, and industry certifications to accomplish high quality nital etch processing.
We offer the following types of service:
- Nitric Acid based standard processing with or without a post processing Bake cycle.
- Preparatory Hydrochloric processing for Tool Steel followed by standard processing.
- Ammonium Persulfate based processing without a post processing Bake cycle (this is our alternative process).
Note: MTC has an in-house bake capability that is certifiable to AMS 2759/9.
The following are examples of nital etch related specifications that MTC is approved to perform:
- AMS 2649
- EIM Code 5
Common types of parts that MTC performs nital etch on are: shafts, gears, splines, bearings, and journals, etc.
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