This study examined the effects of ceramic tool materials on the surface roughness and cutting force when low-carbon resulfurized free-machining steels were plunge-machined. The Tool materials used for the study were 9 kinds in total; 7 kinds ceramics-TiN, TiC, HfO
2, ZrN, Al
2O
3, ZrO
2 and La
2O
3-and a high-speed steel (Fe
3C) and a cemented carbide (WC+Co).
(1) Surface roughness and cutting force are the smallest in the ZrO
2 tool, increasing in the order of TiN, ZrN, Al
2O
3, TiC, HfO
2, WC+Co, La
2O
3 and Fe
3C tools.
(2) ZrO
2, TiN, ZrN and Al
2O
3 tend to adhere selectively to manganese sulfide inclusions in steels, resulting in the formation of MnS films over the rake face of tools. On the other hand, HfO
2, WC+Co, Fe
3C and La
2O
3 tend to adhere selectively to the ferrite phase, forming a kind of built-up edge, whereas TiC hardly to manganese sulfide inclusions and ferrite phase.
(3) Surface roughness and cutting force decrease in proportion to the area percentage of MnS films formed over the rake face of tools, because the MnS films play a role as a lubricant.
(4) Adhesion of manganese sulfide inclusions to tools may not only stem from physical properties such as surface roughness of the tools but also from chemical bonding.
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