Improvement of Wear Resistances of AISI 316L Austenitic Stainless Steels by Anodic Nitriding

Abstract

The nitriding of AISI 316L stainless steels has been carried out at anodic potential in a space enclosed by an active screen that consists of two cylinders with different diameter. These two cylinders made up a hollow cathode in a discharge system. Nitriding experiments were carried out on AISI 316L stainless steel at 450°C for times ranging from 1 to 24h in ammonia atmosphere. The intensity of electron bombardment on the surface of sample was low due to the anodic sheath, the disadvantages attached to conventional plasma nitriding were completely avoided. The phase composition, the thickness and the surface topography of the nitrided layer, as well as its hardness, were investigated by X-ray diffraction, scanning electron microscopy and a micro-hardness tester. The surface microhardness values and the thickness of the hardened layers increased as the nitriding time increased. Tribology properties of the untreated and nitrided 316L stainless steel have been investigated using a ball-on-disc tribometer with AISI52100 ball as the counterface. The results showed wear resistance of the AISI 316L stainless steels were greatly increased by anodic nitriding, owing to the strengthening effect of expanded austenite formed in the modified surface layer.

Microstructure, Mechanical and Tribological Behaviour of Aisi 316l Stainless Steel During Salt Bath Nitriding

“…4, we know that the hardness of alloying elements nitride phase's fine particles (S-phase, CrN and γ' -Fe4N ) in the surface of nitrided sample during salt bath nitriding is more than 1100 HV0.025, that is about six times harder than that of the untreated one. Thus, the nitrided sample was expected to have better resistance to wear [73][74][75][76].…”