GMNA GMN11222 PDF

This is a procedure for determining and rating the level of retained austenite present in the hardened case of nodular (ductile) cast iron camshafts.

Retained austenite is a microstructural phase resultant from a heat and quench hardening operation. It is soft and unstable and is often undesirable in high-precision machine components such as camshafts.

The intent of this document is to provide a standardized method of preparing metallographic samples for determining the amount of retained austenite in the microstructure, and to rate it on a scale of 0 to 4.

A series of 4 photomicrographs of nodular cast iron with progressive levels of retained austenite are used for evaluation. This method is preferred when compared to a quantitative measurement method such as x-ray diffraction and image analysis due to high financial cost and sample size requirements.

This document describes the specific procedures for sectioning the hardened camshaft lobes for analysis. However, the basic principle and analysis can be applied to any case hardened cast iron materials with similar microstructures.

Note: Nothing in this test method supersedes applicable laws and regulations unless a specific exemption has been obtained.

Note: In the event of a conflict between the English and domestic language, the English language shall take precedence