Microstructural examination of a nitrided part is the most commonly used method for evaluating nitriding material and process performance. Microstructural evaluation also helps to validate that the process ran as intended and produced the desired nitrided case characteristics. However, sample preparation is often complicated by the partial or complete breakaway of the compound layer and may affect the accuracy of the conclusions made. A set of experiments was performed to evaluate the effect of two saw cutting methods, the use of metal foil for sample mounting, and the use of Ni plating before cutting. Microstructures of 12 experimental conditions were analyzed. Recommendations were made for the nitrided sample preparation best practice to analyze compound layer uniformity and thickness.

Developing heat treat systems and control plans that produce consistent direct harden (quench and temper) results with a high percent martensite and the corresponding proper mechanical properties is challenging for large components or large batch sizes. In this study, large section bars in alloys suitable for water quenching were austenitized and quenched under controlled flow conditions. The bars were primarily examined by several as-quenched hardness versus depth traverses in order to be sure localized non-martensitic regions (soft areas) would be detected. The tests allowed for some key insights into defining the adequacy of direct harden water quench systems, including the idea of agitation thresholds required for each alloy grade or hardenability level to prevent soft spots (spotty hardening) on large section steel components.

Gas Nitriding is a common industry process which can improve the hardness, wear resistance, and fatigue strength of steel components. Proper surface activation is reported to be critical in achieving a uniform and repeatable nitriding response, but little data is available to compare various activation techniques for common nitriding alloys. This paper reports the early hour compound layer formation for six activation techniques on both a low alloy steel and a specialized nitriding steel. Both grades of steel showed the best performance when a multi-stage nitride washer was used to prepare the surfaces. Two other processes, namely nitric acid etching and a neutral wash and rinse cycle, were also shown to provide acceptable early hour performance for both alloys under the test conditions in this study.