On the impact of tool material and lubrication in ball end milling of ceramic foams

High porosity materials, such as ceramic foams, can be used for several applications spanning from thermal insulators, biomedical implants, molten metal filters, and others. The general practice is to adjust the shape of those ceramic foams in a pre-sintering stage to obtain complex shapes. This work aims to investigate the workability of ceramic foams in a post-sintering condition as an alternative way to overcome premature product failure during production and inhomogeneous shrinkage during sintering. An experimental campaign of ball end milling of alumina-based ceramic foams in a sintered state was carried out herein. Two different tool materials (aluminum oxide-based, diamond-coated) have been tested using two levels of spindle speed under minimum quantity lubrication (MQL) and flood lubrication regimes. The most important findings are: (i) the influence of lubricant is more pronounced analyzing the tool wear, but it has a smaller effect on surface characteristics of the workpiece, (ii) higher spindle speed improves workpiece surface quality (ii) diamond coated tools are the best available choice in terms of both tool wear and surface quality.