Interactions in silicon nitride ceramics vs. steel contact under fretting conditions

S. Novak, G. Dražić, M. Kalin, J. Vižintin

Wear 225/229 (1999) 1276–1283.

Abstract

The wear of silicon nitride and bearing steel under oil-lubricated fretting conditions was investigated and the mechanisms involved studied. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and Auger spectroscopy (AES) were employed to analyse the surface layers of the wear scars. The increased temperature at the contact of ceramic balls and steel plates induced tribochemical reactions of the material with chemical species from the environment. In contrast to the tribolayer created under non-lubricated conditions where oxidation of silicon nitride and steel is a wear determining mechanism, at oil-lubricated contacts carbonisation of steel due to oil decomposition takes place.

V prispevku so predstavljeni mehanizmi freting obrabe v kontaktu med jeklom in keramiko iz silicijevega nitrida. Amplitude pomikov so bile med 5 in 50 m, časi preizkusov pa med 10 in 360 minut. Preizkusi so bili opravljeni pri frekvenci 210 Hz v suhih in z oljem mazanih kontaktih. Za analizo površin smo uporabili optično, elektronsko in transmisijsko mikroskopijo ter energijsko in Augerjevo spektroskopijo. Ugotovljeno je bilo, da pri mazanih pogojih pride zaradi tribokemijske reakcije do prehoda iz velike v majhno obrabo pri kritični amplitudi pomika 25 m. Povsem drugačen pa je bil mehanizem obrabe v suhih pogojih, kjer obraba z večanjem amplitude pomika narašča. Dominatni mehanizem je oksidacija silicijevega nitrida, ki povzroči na obrabni površini nastanek večjih otokov amorfnega silicijevega oksida, v katerem se nahajajo precipitati železovih oksidov. Obraba je bila v suhih pogojih za red velikosti večja kot pri mazanih pogojih.

Keywords: wear, silicon nitride, steel, tribochemical reaction

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