Study on the microstructure and properties of powder-forged gear materials

Combining the advantages of powder metallurgy and precise forging technology, the powder forging (PF) technique can produce the nearly net-shaped products with the high precision and the outstanding mechanical properties efficiently. In this study, the preformed compact was processed by compacting, degreasing, and sintering, using a kind of gear material (Q61) as raw material, and finally the dense standard blocks was obtained by closed mold hot forging. The microstructure and physical properties of Q61 powder-forged blocks were characterized, including density, hardness, tensile properties, and fatigue properties. The results indicate that, the full densification blocks are prepared with the density of 7.87 g·cm^-3. The Rockwell hardness of the air-cooled block is HRC 25.3, which is capable for machining and shaping; while the quenched block shows the high hardness with HRC 62.1, which can omit the conventional carburizing process. The tensile strength of the standard blocks is 1052.8 MPa, which can match those of common gear steels. Then, the planetary spur gears are processed by powder forging, and the gear teeth by high-frequency quenching shows the equivalent hardness as that of carburizing gear. This is an exploratory study for the development of powder forged technique in China.