Tool wear of aluminum/chromium/tungsten/silicon-based-coated solid carbide thread milling cutters in thread tapping of chromium-molybdenum steel

The helical milling method with thread milling cutters in thread tapping is effective against problems associated with tapping chips. In this study, chromium-molybdenum steel (ISO 34CrMo4, AISI 4137) was helical milled with two physical vapor deposition (PVD)-coated cemented carbide end thread milling cutters in order to determine effective tool materials for tapping chromium-molybdenum steel. The coating films used were (Al60, Cr25, W15)(C, N)/(Al53, Cr23, W14, Si10)(C, N) and commercial (Al, Cr)N coating films. The inner layer of the (Al60, Cr25, W15)(C, N)/(Al53, Cr23, W14, Si10)(C, N) coating system is (Al60, Cr25, W15)(C, N) coating film, and the outer layer is (Al53, Cr23, W14, Si10)(C, N) coating film. In order to identify an effective tool material for thread tapping of chromium-molybdenum steel, tool wear was experimentally investigated. The following results were obtained: (1) The critical scratch load measured value by a scratch tester for the (Al60, Cr25, W15)(C, N)/(Al53, Cr23, W14, Si10)(C, N) coating film was over 130 N. (2) In thread tapping of chromium-molybdenum steel at a cutting speed of 1.00 m/s, the tool wear width of the (Al60, Cr25, W15)(C, N)/(Al53, Cr23, W14, Si10)(C, N)-coated tool was smaller than that of the (Al, Cr)N-coated tool. (3) It was possible for the (Al60, Cr25, W15)(C, N)/(Al53, Cr23, W14, Si10)(C, N)-coated thread milling cutter to perform stable tapping for a long period. Therefore, the new (Al60, Cr25, W15)(C, N)/(Al53, Cr23, W14, Si10)(C, N) coating film can be used as a tool material in thread tapping of chromium-molybdenum steel.