Ion nitriding of steels

Abstract

This paper deals with the ’’ion-nitriding’’ method of nitriding various grades of steels in a laboratory model furnace. Four different grades of steels such as AISI 4140, Nitralloy 135 Mod., high-speed steel M2 and stainless steel 304 were ion nitrided at different temperatures with cycle times ranging from 1 to 36 h in a gaseous mixture of nitrogen and hydrogen under a total pressure of 7 Torr (9.1×103 Pa). Results obtained with 4140 steel show that ion nitriding at 950°F is much faster than conventional gaseous nitriding. At a given temperature of ion nitriding, case depth versus treatment time follows a parabolic law for all four grades of steels. Current theoretical and experimental evidence has been used to explain different nitriding rates observed for various steels. Finally results of ion nitriding performed at 750°F have been presented to show the versatility of this process.