Milling of alumina-based ceramic foams: tool material effects

Porous ceramics are recognized to have the potential to be used for a wide variety of industrial applications, such as catalyst support and molten metal filter. It is a common practice to adjust the shape of ceramics in a pre-sintering stage in order to obtain various configurations but some limitations due to premature failure of the product, marked tool wear or inhomogeneous shrinkage during processing stages may arise, whenever a complex shape is requested. Almost the same happens in the case of post-sintering stage ceramics machining leading, in most cases, to an inefficient process characterized by a severe tool wear and poor final product quality. Such problems, related to tool material, material removal modes and hence process parameters represent a huge limitation for many industrial applications of the above materials. Milling of alumina-based ceramic foams in a sintered state is the focus of the present work. An experimental campaign has been carried out at fixed axial depth of cut, feed rate, number of passes, spindle speed and under flood lubrication regime varying tool material (aluminum oxide-based, diamond-coated). Tool wear mechanisms and final product quality have been investigated through surface analysis in order to verify the workability of alumina based ceramic foams and the related tool wear.