Influence of Mechanical Pressure and Temperature on the Chemical Interaction Between Steel and Silicon Nitride Ceramics

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Abstract
The chemical interaction between a Si3N4ceramic, with Al2O3and 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.