scope:

This standard specifies standard procedures and requirements for the detection and classification of localized overheating on ground surfaces by chemical etch methods. Surface temper etch inspection is also useful for the detection of surface anomalies that result from post-heat treatment machining such as hard turning, milling and edge breaking (deburring) processes. Surface metallurgical anomalies caused by carburization or decarburization are also readily detectable with this process. Some methods which have been used in the past are no longer recommended. Specifications should be changed to use the methods in this standard. These etching methods are more sensitive to changes in surface hardness than most hardness testing methods. This standard applies to steel parts, such as gears, shafts, splines, and bearings. It is not applicable to nitrided parts and stainless steels and alternative methods should be considered. NOTE This process, although at times called "nital etch", should not be confused with other processes also known as "nital etch". The surface temper etch procedure is to be performed after grinding and before additional finishing operations, such as superfinishing, shot peening and honing.