Tool wear when tapping operation of compacted graphite iron

The automotive industry has made increasing use of compacted graphite iron in the manufacture of several components traditionally made of gray iron. However, in some cases, the poor machinability of compacted graphite iron compared to that of gray iron renders production costs uncompetitive. Several researches have focused on the machinability of compacted graphite iron, particularly in turning, milling and drilling operations. However, tapping, which is a more complex operation, has received little attention. The main objective of this work is to investigate the performance of cemented carbide taps when tapping ASTM A450 compacted graphite iron using TiAlN-coated M13 x 1.5 taps with four straight flutes. Cutting tools with different wear levels were analyzed after their use in machining engine cylinder blocks. Tool wear was measured and analyzed using scanning electron microscopy and optical microscopy. The main wear mechanisms observed were adhesion and abrasion.