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. Vleugels and O. Van Der Biest Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, De Croylaan 2, B-3001 Leuven, Belgium (Received 16 April 1999; accepted 28 March 2000)

The chemical interaction between a Si3N4 ceramic, with Al2O3 and MgO sintering additives, and DIN 100Cr6 steel was studied by means of static interaction couple experiments between 500 and 1200 °C. At 500 °C, the ceramic was chemically stable in contact with the steel. In the temperature range between 700 and 1100 °C, the silicon nitride dissociated in contact with the steel. The Si dissolved and diffused into the steel, whereas a nitrogen pressure built up in the micropores at the interface, limiting and inhibiting the reaction rate. The strength of the obtained interfacial bond was too low to withstand the residual stresses formed during cooling, and therefore, the interaction couples fell apart during cooling. Above 1100 °C, the nitrogen also dissolved and diffused into the steel, enhancing the overall rate of interaction. A strong interface was formed, resulting in a well-defined interaction layer on the ceramic side of the interaction couple. The mechanical pressures on the interaction couples were adjusted to study the influence of plastic deformation of the steel on the chemical interaction. Higher contact pressures resulted in more homogeneous and uniform interaction layers. The reactivity of plastically and elastically deforming steel, however, was found to be the same.

I. INTRODUCTION

Silicon nitride ceramics are considered for use in many mechanical applications, especially for rolling contact systems, like roller bearings, or for reciprocating engine parts, like valves, valve seats, valve guides, and various industrial wear parts.1–4 It should however be pointed out that today’s most commonly used material for machine parts is steel. Therefore, wherever a ceramic component is introduced into a mechanical system, it is very often in contact with steel. As a consequence, various forms of wear of steel in contact with silicon nitride are of great interest for the prediction and evaluation of the behavior of steel–ceramic contacts. Engineering ceramics are traditionally considered to be particularly resistant to chemical wear. However, it is becoming clear that the interactions of the ceramic with the environment and the counterbody play a critical role in determining the wear performance.5–12 The evidence for tribochemical reactions and their consequences on the wear and friction behavior in various ceramic contacts were reported many times, but the explanations for the J. Mater. Res., Vol. 15, No. 6, Jun 2000

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physical or chemical reasons for the reaction processes differ and are often contradictory. In some cases, the tribochemical reactions are attributed to high temperatures at the contact, and in other cases, to mechanical effects, usually pressure, plastic deformation, dislocations, shear stress, etc. However, to fully understand the tribochemic