Effect of workpiece geometry on the uniformity of nitrided layers

The growth behavior of plasma-nitrided layers on workpieces with complex ge ometry was systematically investigated. AISI 316 stainless steel pellets wi th different heights were nitrided under a mixture of N-2-80% H-2 at differ ent temperatures (673, 773 and 843 K) and pressures (100 and 500 Pa). Signi ficant differences in thickness and hardness of the resulting nitrided laye rs were observed as a function of nitriding parameters. The thickness of ni trided layers increased with sample height, excepted those nitrided at 843 K. The diameter of eroded rings, commonly observed on nitrided samples, var ied with coupon height. Changes in both layer thickness and eroded ring dia meter are presently addressed based on the thermal balance and charge densi ty that take place near the edges of the samples. (C) 2001 Elsevier Science B.V. All rights reserved.