Improvement of cutting tool life by AIN deposition on the tool

SCM415 steel was machined with carbide tools in as hot rolled condition and after normalizing heat treatment. In the as-rolled sample, a significant amount of AI and N existed as solid solution; whereas, in the normalized sample, AI and N existed as AIN precipitates. Reduction of tool wear for the as-rolled sample was observed. On the rake face of the tool machined for the as-rolled sample, the presence of AIN deposit was observed. It is believed that AI and N in solid solution form AIN deposit on the tool face due to temperature rise during machining, and that the deposition of the AIN layer on the tool face prevents diffusion between the tool and chip and reduces tool wear.