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A kind of Ti(C, N)‐based cermet tool material was prepared by microwave sintering. The influence of metal phases (Ni, Co, and Mo) on densification and mechanical properties was studied by orthogonal test. The results indicated that Co was more significant in improving relative density and fracture toughness than Ni, while Ni and Co had the similar effects on increasing the hardness of Ti(C, N)‐based cermet. Mo can improve fracture toughness but decrease hardness. Ti(C, N)‐based cermet with 6 wt% Ni, 6 wt% Co and 6 wt% Mo (TN6C6M6) had the optimal comprehensive mechanical performances, and its fracture toughness and hardness were better than that of Ti(C, N)‐based cermet prepared by conventional sintering. The increasing of sintering temperature promoted the uniformity of microstructure and significantly improved densification and hardness of the Ti(C, N)‐based cermet. The highest fracture toughness of TN6C6M6 (12.41 ± 0.33 MPa·m1/2) was achieved when sintered at 1600°C. For the microwave‐sintered Ti(C, N)‐based cermet, heat preservation period had little effect on densification. The relative density can reach up to 98.6% even though the heat preservation period was 0 minute. [ABSTRACT FROM AUTHOR]

Fine-grained Al 2 O 3 /SiC composite ceramic tool materials were synthesized by two-step microwave sintering. The effects of first-step sintering temperature (T1), content and particle size of SiC on the microstructure and mechanical properties were studied. It was found that the sample with higher content of SiC was achieved with finer grains, and the incorporation of SiC particles could bridge, branch and deflect the cracks, thus improving the fracture toughness. Higher T1 was required for the densification of the samples with higher content of SiC (>5 wt%). The sample containing 3 wt% SiC particles with the mean particle size of 100 nm, which was sintered at 1600 °C (T1) and 1100 °C (T2) for 5 min had the fine microstructure and optimal properties. Its relative density, grain size, Vickers hardness and fracture toughness obtained were 98.37%, 0.78 ± 0.31 μm, 18.40 ± 0.24 GPa and 4.97 ± 0.30 MPa m1/2, respectively. Compared to the sample prepared by single-step microwave sintering, although near full densification can be achieved in both two methods, the grain size was reduced by 36% and the fracture toughness was improved by 28% in two-step microwave sintering. [ABSTRACT FROM AUTHOR]

SiC whiskers (SiC w)-reinforced α/β-SiAlON ceramic tool materials were synthesized via spark plasma sintering (SPS). A comprehensive study was conducted on densification mechanism, phase composition, microstructure, mechanical properties, and wear resistance of the SiC w /α/β-SiAlON composites. The results indicated that SiC w constrained the densification process and impeded the growth of SiAlON grains, and the introduction of SiC w significantly enhanced mechanical properties of the α/β-SiAlON ceramic. The composite containing 28 wt% SiC w synthesized at 1700 °C showed well mechanical properties, with a density of 3.35 g/cm³, Vickers hardness of 19.38 ± 0.33 GPa, and fracture toughness of 7.35 ± 0.27 MPa m1/2.The principal toughening mechanisms of SiC w /α/β-SiAlON included crack deflection, branching, bridging, as well as transgranular fracture and whisker pullout. The addition of SiC w improved the wear resistance of α/β-SiAlON ceramic. Compared to those without whiskers, the wear volume and wear rate were decreased by 38.8 %. [ABSTRACT FROM AUTHOR]

α/β-SiAlON composite ceramics using powders mixed through different processes were prepared via spark plasma sintering. Effects of different powder mixing methods (ball-milling and ultrasonic vibration with mechanical stirring), ball-milling media (Al 2 O 3 and Si 3 N 4 balls), and mixing times (12 and 24 h) on the components and morphology of mixed powders, phase composition, microstructure, and mechanical properties of α/β-SiAlON ceramics were studied. Results indicate that additional oxides are mixed to powders when ball-milled with Al 2 O 3 balls, leading to an increase in the amount of amorphous glass and a decline in α/β ratio and mechanical properties. These effects were reduced when powders were ball-milled with Si 3 N 4 balls, and α-SiAlON content and fracture toughness increased significantly. Moreover, α/β-SiAlON ceramics that underwent ultrasonic vibration with mechanical stirring exhibited the highest hardness and oxidation resistance at high temperature, and their α/β ratio was close to expected value. [ABSTRACT FROM AUTHOR]

A fine-grained Al 2 O 3 -based ceramic tool reinforced with SiC particles (SiC p) and SiC whiskers (SiC w) was prepared by two-step microwave sintering (TSMS, 1650 °C/5 min, 1100 °C/5 min). Effects of the content of binder polyvinyl alcohol (PVA) and molding pressure on relative density, mechanical properties and microstructure of the ceramic tool were studied. As the PVA content and molding pressure were 1.5 wt% and 150 MPa, respectively, the best properties were obtained. Compared to other researches on microwave sintering, the PVA content was reduced by 50%, which effectively extended the service life of the thermal insulation device and was beneficial to the densification of the ceramic tools. When the SiC particles and whiskers were 3 wt% and 1 wt%, the relative density, Vickers hardness, fracture toughness and grain size were 99.8 ± 0.1%, 18.8 ± 0.3 GPa, 4.8 ± 0.3 MPa m1/2 and 1.3 ± 0.2 μm, respectively. Compared with the single-step microwave sintering (SSMS) (1650 °C/5 min), the grain size was reduced by 35% while the Vickers hardness and fracture toughness were increased by 9.3% and 29.7%, respectively. The fine grains resulted from two-step sintering, and the pinning and pull-out effects of SiC whiskers contributed to the improvement of fracture toughness. [ABSTRACT FROM AUTHOR]