Effect of workpiece geometry on the uniformity of nitrided layers

The growth behavior of plasma-nitrided layers on workpieces with complex geometry was systematically investigated. AISI 316 stainless steel pellets with different heights were nitrided under a mixture of N2–80% H2 at different temperatures (673, 773 and 843 K) and pressures (100 and 500 Pa). Significant differences in thickness and hardness of the resulting nitrided layers were observed as a function of nitriding parameters. The thickness of nitrided layers increased with sample height, excepted those nitrided at 843 K. The diameter of eroded rings, commonly observed on nitrided samples, varied with coupon height. Changes in both layer thickness and eroded ring diameter are presently addressed based on the thermal balance and charge density that take place near the edges of the samples.