A Preliminary Machinability Study of Flake and Compacted Graphite Irons with Multilayer Coated and Uncoated Carbide Inserts

Abstract

Compacted graphite iron (CGI) is considered to be one of the most promising materials for many automotive applications and has adopted by some automotive companies. Comparing to widely used flake graphite iron (FGI), CGI has superior physical and mechanical properties. The main drawback of this material is known to be its poor machinability. A preliminary study on flank and crater wear was conducted by dry turning experiments with both FGI and CGI using uncoated WC tools and multilayer coated tools. Confocal Laser Scanning Microscopy (CLSM) was used to investigate worn areas of the cutting tools. Despite of the reported poor machinability of CGI, our turning experiments showed that both flank and crater wear were higher for FGI compared to CGI when using uncoated WC tools at the cutting speed of 150, 250 and 350 m/min. An unexpected adhesion layer on the flank side of carbide inserts was observed when turning CGI, which believe to protect the flank surface and reduce flank wear. The adhesion on rake face concentrated on the cutting edge when turning CGI while the sporadic attachments of work materials are observed throughout the rake interface with FGI. In contrast, no adhesion layer was presented when both FGI and CGI were turned using multilayer coated tools, which yielded more flank and crater wear when turning CGI.