Surface Abuse Associated with Finish Turning of Gray Cast Iron with Ceramic Tools

Abstract

Machining trials were carried out on a G-17 cast iron using round and square-shaped pure oxide (≥99 vol. % Al₂O₃ + ≤ 1 vol. % ZrO₂), mixed oxide (70 vol. % Al₂O₃ + 30 vol. % TiC) and silicon coarbide whisker-reinforced (75 vol. % Al₂O₃ + 25 vol. % SiC) ceramic tools in order to study the extent of damage on the machined surfaces. G-17 is a BS 1452 (1977) designation and equivalent to ANSI/ASTM A48-83 grade 40 designation. The test results show that the round-shaped ceramic tools produced better surface finish and less damage than square inserts under the cutting conditions investigated due to their increased nose radius, which increased the tool-workpiece contact area during machining. The surface finish deteriorates with prolonged machining and an increase in the depth of cut. The hardness values of the surface layer were generally above the average hardness value of the base material due to the hardening of the surface layer as a result of the high pressure, compressive stress and temperatures generated at the cutting edge during machining. A higher rate of hardening was observed when machining with the mixed oxide and SiC whisker-reinforced ceramic tools due, perhaps, to the relatively high temperatures generated at the higher cutting speed (500 m/min.) used.

Presented at the 50th Annual Meeting in Chicago, Illinois May 14–19, 1995

KEY WORDS:

• Ceramics
• Turning
• Cutting
• Surface Roughness
• Finishing

Notes

Presented at the 50th Annual Meeting in Chicago, Illinois May 14–19, 1995