Effect of Sintering Temperature on Microstructure and Mechanical Properties of Fe–4Ni–0.8Mo–0.6C Steel Small‐Module Gears Fabricated by Micrometal Injection Molding

Abstract

Small‐module gear is the key basic component of equipment in the fields of aerospace, weapon equipment, communication, and so on, which is an important embodiment of the high‐end intelligent equipment manufacturing level. Herein, the small‐module gears are fabricated by micro‐metal injection molding (micro‐MIM) and the microstructure and mechanical properties of the gears are characterized. The small‐module gears are successfully molded, debounded, and sintered based on the feedstock with 58% powder loading. The structure and mechanical properties of the samples are investigated in relation to the sintering temperature for the determination of optimum sintering conditions. The results show that the relative density and average grain size increase with the increment of sintering temperature, and the maximum relative density of 97.6% is obtained at the sintering temperature of 1320 °C. The tensile strength and hardness of the sintered sample are 2034 MPa and 709 HV at 1320 °C, respectively, presenting the most desirable mechanical properties, which are attributed to the formation of martensite with high strength and hardness at the expense of pearlite and ferrite and the alloy carbide precipitations in the microstructure. Herein, important guidance to develop low‐cost and high‐performance small‐module gear is provided by using micro‐MIM.