Microstructure and Material Analysis of Worn WC-Co Ball-End Mills

The objective of this study is to examine the relationship between microstructure and material content at critical locations of used WC-Co ball-end mills. The performance of three similar tools was tested at identical cutting conditions. From each tool, three samples were cut from the same positions on the WC-Co ball-end mills at key locations. Scanning Electron Microscopy (SEM) was used for observation of the microstructure of material and three methods were used to determine the chemical compositions of each tool. The first method used to examine the chemical composition was Energy Dispersive Spectrometry (EDS). Higher accuracy chemical analysis using Wave Dispersive Spectrometry (Microprobe) techniques and Slice-Averaged Wet Chemistry (ICP) results were also completed to verify trends and chemical contents. The results of this study showed that the microstructure is closely related to the cobalt content. Moreover, cobalt losses resulting from the machining process as well as phenomena resulting in microstructure defects in the manufacturing stage of the carbide were evident in worse performing tools. Furthermore, differing grain-growth inhibitor contents of each tool might have led to additional performance differences.