Ti (C, N) -based cermets are widely used as cutting tool materials because they have high hardness and excellent welding resistance compared to cemented carbide. However, its strength and toughness are lower than those of cemented carbide, and chipping and fracture are likely to occur during cutting. In order to improve the fracture resistance of cermets, methods such as adding a third element such as tungsten and optimizing the nitrogen content have been often used, but they can be used for harsh cutting due to higher efficiency. For that purpose, it is indispensable to further improve the fracture resistance. Therefore, the author has been developing and commercializing high-strength ultrafine Ti (C, N) -based cermets with a Ti (C, N) particle size of 0.5 μm or less. Here, we report on the improvement of characteristics by the development of ultrafine cermet and the manufacturing technology for commercialization.

Synchronizer hubs are powder metal parts often used in vehicles for manual and dual clutch transmissions. The synchronizer hub, which synchronizes mechanical connections to shift gears, needs high strength and durability. Although these properties can be improved by carburization or partial hardening, such processes can lead to increased costs. We used a roller hearth high temperature furnace that can be cooled rapidly, and optimized the material composition and sintering conditions. Thus, we have succeeded in the development of synchronizer hubs without requiring the second hardening process.

In this study, the effect of B, P, and Si content on the amorphous forming ability (AFA), B_s, and H_c was investigated in Fe_78.7Nb₆(B_15-x-yP_xSi_y)₁₅Cr_0.3 (2.0 ≦ x ≦ 4.5, 2.0 ≦ y ≦ 4.5) alloys using metallic ribbons produced by a single-roller melt-spinning method. The Fe_78.7Nb₆B₉P₃Si₃Cr_0.3 alloy with a high AFA of 69 μm exhibited excellent magnetic characteristics, B_s of 1.42 T and H_c of 9.3 A/m.

Precursor Fe_78.7Nb₆B₉P₃Si₃Cr_0.3 amorphous alloy powder was prepared by the gas atomization method using high pressure water for rapid quenching. The as-atomized particle as a with a single amorphous phase was observed from a cross sectional image and SAED pattern in the Fe_78.7Nb₆B₉P₃Si₃Cr_0.3 alloy powder. In addition, the Fe_78.7Nb₆B₉P₃Si₃Cr_0.3 alloy powder after nanocrystallization at 873 K achieved both high B_s of 1.40 T and low H_c of 55 A/m compared to commercial amorphous, and nanocrystalline alloys. Furthermore, the Fe_78.7Nb₆B₉P₃Si₃Cr_0.3 nanocrystalline alloy powder core exhibited superior DC-bias electromagnetic characteristics compared with commercial amorphous or nanocrystalline alloy powder core. The newly developed Fe_78.7Nb₆B₉P₃Si₃Cr_0.3 alloy powder with excellent magnetic softness is suitable for improving the performance of inductor using magnetic components.