In their natural state within the earth’s crust, even the most abundant metals are rarely useful. To become viable in products across the spectrum of industry, ores need to be smelted, refined, and subject to a plethora of other processes. Even after refinement, further actions are often needed to enhance the metals. One such example in aerospace applications is ion nitriding.
The focus of SAE AMS 2759/8B-2018: Ion Nitriding, this process is typically applied to alloy steels, tool steels, corrosion resistant steels, carbon steels, ferrous powder metal products, and other ferrous alloys. By diffusing nitrogen into the surface of a metal through ionized molecules of gas, ion nitriding increases surface hardness and wear resistance, and it reduces the coefficient of friction.
Ion nitriding is quite successful in providing these results. In fact, when compared with the alternative method of gas nitriding (ion nitriding is also known as plasma nitriding), ion nitriding sees higher surface, case, and core hardness, and its treated metals are noted by their excellent wear resistance—the ion plasma nitriding process produces a dense, nonporous, very hard but not brittle compound zone—and great surface finish. Ion nitriding, due to being performed at a lower temperature and under a vacuum, has less distortions.
Ion nitriding is applied to gears, crank shafts, feed screw, camshafts, cylinders, drilling tools, and various other components composed of ferrous alloys.
Therefore, SAE AMS 2759/8B-2018 is intended for use with ferrous alloys. As an aerospace material specification, SAE AMS 2759/8B-2018 establishes the guidelines and procedures for producing a hard, wear resistant ion nitride surface on steel parts.
SAE AMS 2759/8B-2018 covers a range of technical information, including the equipment, thermocouples, prior heat treatment and stress relieving applications, and pyrometers. Pyrometers, infrared or otherwise, measure surface temperatures that are too hot to be reached or touched. SAE AMS 2759/8B-2018 also outlines parameters for the ion nitriding process and post nitriding operations.
Processes covered by the specification are classified as Class 1 (0.0005 inch maximum white layer thickness permitted) or Class 2 (0.001 inch maximum white layer thickness permitted)
In using SAE AMS 2759/8B-2018, purchasers are expected to supply a range of information to the nitride processor. This includes the size of parts, incoming core hardness, incoming part heat treat condition, prior heat treatment information, total case depth, areas to be nitride, compound zone layer depth, and grind stock allowances, among others.
SAE AMS 2759/8B-2018: Ion Nitriding is available on the ANSI Webstore.