Influence of Negative Substrate Bias Voltage on Properties and Cutting Performance of TaWSiN Coating Films Deposited using Magnetron Sputtering Ion Plating
As these difficult-to-cut materials have to be machined efficiently to improve productivity, the tool materials must be wear resistant. To clarify the influence of negative substrate bias voltage on both the mechanical properties of TaWSiN coating films, this study measured the hardness and the scratch strength (critical load measured by scratch tester) of the TaWSiN coating film formed on the surface of a substrate of cemented carbide ISO K10 by the magnetron sputter ion plating process. The hardened steel AISI D2 was turned with the TaWSiN-coated cemented carbide tools. The tool wear of the TaWSiN-coated cemented carbide was experimentally investigated and compared with that of the TaWN-coated cemented carbide. The following results were obtained: (1) The microhardness of the TaWSiN coating film was slightly less hard with the decrease of the negative substrate bias voltage. (2) The critical scratch load of the TaWSiN coating film increased with the decrease of the negative substrate bias voltage. (3) In cutting hardened steel at a cutting speed of 1.00 m/s, the wear progress of all types of TaWSiN-coated tools was lower than that of the TaWN-coated tool. (4) Within the range of most cutting speeds from 0.67 m/s to 1.50 m/s, the tool life of the coated tool deposited using the negative substrate bias voltage of 105 V was the longest among the four types of TaWSiN-coated tools. It was thus confirmed that the TaWSiN coating film, which decreases the negative substrate bias voltage of 105 V, has both high hardness (microhardness of 2690 HV0.25N), and good adhesive strength (critical load of 90N), and can be used as a coating film of WC-Co cemented carbide cutting tools.
Keywords: Cutting, Coating Technology, Physical Vapor Deposition Coating Film (PVDCoating Film), Tantalum/Tungsten/Silicon-based Coating Films (TaWSiN Coating Film), Hardened Steel.