Machining of novel alumina/cyanoacrylate green ceramic compacts

Abstract

Research at Nottingham Trent University has led to the invention of an innovative technology, PRIME, which produces novel alumina/cyanoacrylate ceramic compacts that can be machined using conventional methods, such as drilling, turning and milling. Powder reaction injection moulding engineering (PRIME) is a unique solution to the problems associated with the debinding of conventional waxes or polymeric binders used in powder moulding, since the cyanoacrylate binder (superglue) employed in PRIME de-polymerises back to a monomer. Traditionally, debinding of waxes and polymeric binders used in powder injection moulding is a very costly part of the process. Thermal degradation and solvent wicking of polymeric binders can take hours or even days, but cyanoacrylate has major advantages because of its ability to unzip in minutes when exposed to temperatures greater than 180 °C. Also can be collected for reuse. This enables a simple approach to powder moulding and a significantly decreased processing time. Feedstock was prepared consisting of a high volume fraction of powder (0.48). Machining before sintering of a ceramic (i.e. in the green state) represents an alternative to other shaping processes, and offers a high degree of flexibility and economic efficiency for the machining of ceramic parts. The study of green machining of a new ceramic material is also important for the future development and application of the material, since this is a common manufacturing process in many industries. The fragility of conventional ceramic green compacts generally provides considerable difficulties when machining. The alternative of diamond grinding the fired product is an expensive process, which is limited in the complexity of shapes that can be produced. Currently, however, around 80% of all machining of advanced ceramics is carried out in this way. Although new physical and chemical (P&C) machining techniques have been introduced, the practical limitations to their use are high initial investment costs and restrictions on the materials that can be shaped. This paper reports the initial research results, and demonstrates that cyanoacrylate can be used as an effective reactive binder with aluminium oxide to produce compacts that can be machined using conventional carbide tools in order to manufacture engineering parts.