1 Scope
This International Standard specifies procedures and requirements for the detection and classification of localized overheating on ground surfaces by chemical etch methods.
The process described in this International Standard is typically used on ground surfaces; however, it 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 are intended to be changed to use the methods in this International Standard. These etching methods are more sensitive to changes in surface hardness than most hardness testing methods.
This International Standard applies to steel parts such as gears, shafts, splines, and bearings. It is not applicable to nitrided parts and stainless steels. Alternative methods should be considered.
NOTE This process, although at times called “nital etch”, is not intended to 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.