Sliding–wear evaluation of Tufftrided austenitic alloys

Abstract

Tufftriding a selection of austenitic alloys produces in each a reaction zone consisting of three layers. A thin, hard layer, composed essentially of oxide, is formed on the specimen surface. Beneath this is a carbonitride of the γ', M₄(CN) type, with a low carbon/nitrogen ratio. The innermost layer has a much higher carbon concentration, which reaches ∼2%. Wear behaviour, evaluated without lubrication using a pin-on-disc machine, shows a transition from mild wear to severe wear once the applied load exceeds a critical value. Mild wear is associated with the tribological properties of the outer layer. In the severe-wear regime, the wear rate is higher by approximately an order of magnitude; under these conditions the oxide is removed fairly quickly, and wear is controlled by the properties of the underlying carbonitride. The results are compared with those obtained previously for untreated and nitrided alloys, and it is concluded that Tufftriding shows promise as a method of improving the tribological properties of austenitic alloys.