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To improve the tribological properties of the cemented carbide, Ti-MoS/Zr composite coatings were deposited on the substrate surface by medium-frequency magnetron sputtering coupled with multi-arc ion plating. The morphology and fundamental properties of the coatings were examined. Dry machining test on AISI 1045 hardened steel was carried out with the coated tool and uncoated tool. The variation of cutting temperature was tested by a TH5104 thermo tracer. The results showed that cutting speed had a profound effect on the cutting temperature. In low-speed cutting of less than 120 m/min, the cutting temperature was decreased by 18-22% and flank wear resistance was improved by 25-30% in comparison with that of uncoated tool, while in high-speed cutting, there was not much difference in cutting performance owing to the high temperature caused by the elevated cutting speed. Through the analysis of cutting heat distribution theory, two responsible mechanisms are found: as lubricating additive between the tool and chip sliding couple, the Ti-MoS/Zr composite coatings contribute to the decrease of average shear stress on the rake face and the thermal barrier effect in heat conduction. These may result in the decrease of the cutting temperature of tool and chip, and hence the improvement of tool wear resistance. [ABSTRACT FROM AUTHOR]

The initial WC grain-size distribution, as one of the most important factors influencing the properties of alloys, has been focused on for a long time in some fields other than cemented carbides. In the present work, five groups of WC-6Ni cemented carbides were prepared and the effect of initial WC grain-size distribution on the microstructure and properties of the hard alloys was studied. The results indicate that initial WC grain-size distribution has significant influence on the microstructure and properties of WC-6Ni cemented carbides, except density. When the mass ratio of coarse-WC and fine-WC is 7:3, WC-6Ni cemented carbide samples with initial WC grain-size distribution of WC-1(4.8 μm) and WC-4(0.7 μm) show a relatively good combination properties, while the cemented carbide samples with WC-5(0.4 μm) as the fine-WC component exhibit higher values on some properties, mainly hardness and immersion corrosion resistance in acid and alkali. [ABSTRACT FROM AUTHOR]