Influence of alloying elements on the chemical reactivity between Si-Al-O-N ceramics and iron-based alloys
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Influence of alloying elements on the chemical reactivity between Si–Al–O–N ceramics and iron-based alloys J. Vleugels, L. Vandeperre, and O. Van Der Biest Department of Metallurgy and Materials Engineering (MTM), Katholieke Universiteit Leuven, B-3001 Leuven, Belgium (Received 13 December 1994; accepted 11 January 1996)
The chemical interaction between two b 0 –O0 Si–Al –O–N ceramics and a number of iron-based alloys is studied by means of static interaction couple experiments at 1100 and 1200 ±C. The onset temperature of reaction of Si3 N4 with pure iron was found to be at 1095 ±C, which is in good agreement with a calculated temperature of 1033 ±C. During the interaction, silicon and nitrogen from the ceramic dissolve and diffuse into the iron alloy, whereas the remaining aluminum and oxygen form Al2 O3 particles. The interaction between ceramic and iron alloy is reaction controlled. In the initial stage of the interaction, the dissociation rate of the ceramic is the rate-controlling step. After the ceramic/metal interface is isolated from the furnace atmosphere, the nitrogen solution rate into the iron alloy becomes rate controlling. The influence of alloying elements on the reactivity could be related to their effect on the nitrogen solubility in the iron alloy. Ni, Si, and C decrease the nitrogen solubility and decrease the reactivity with the sialon ceramic. Cr and Mo have the opposite effect. The thickness of the interaction layer on the ceramic side of the interaction couple was found to be a function of the calculated nitrogen solubility in the iron alloy at 1 atm nitrogen pressure, making it possible to predict the relative chemical reactivity of a number of iron-based alloys with the same sialon ceramic.
I. INTRODUCTION
Since the introduction of powerful numerically controlled machining centers, the relative importance of cutting time in the total machining cycle of materials increases. Hence there are important benefits to further reduce machining time by increasing the cutting speed and feed. High cutting speeds and feeds generate high mechanical stresses and temperatures at the contact surface between cutting tool and workpiece material. The essential requirements for new cutting tool materials are, in addition to low cost, a high hardness and toughness at elevated temperatures, a good thermal and mechanical shock resistance, a high oxidation resistance, all of these combined with a high chemical stability and compatibility with respect to the workpiece material. In recent years we have seen a continued optimization of existing cutting tool materials or the development of new ones. Ceramics are hard; they retain their hardness and toughness at high temperatures and have a relatively high wear resistance. They are thus interesting potential cutting tool materials. The most promising ceramic materials for high speed turning applications are Al2 O3 - and Si3 N4 -based ceramics. Nowadays, Al2 O3 and Si3 N4 -based inserts are used in high speed turning of gr
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