Papers by Keyword: Sinter-Hardening

Abstract: Synchronizer rings are mechanical components that equalize the gear rotation to be engaged with the sliding sleeve. It is done by the friction property of the synchronizer ring material. Different types of materials are used to manufacture synchronizer rings depending on the application. There are basically two groups of material: dual function, structural and friction properties (Cu-Zn alloys, Al-Si alloys, etc.) and single function, only structural property (rolled and sintered steels, Cu-Zn alloys, Al alloys, etc.). The objective of this work was to propose a solution to the synchronizer ring structural material of a new mechanical transmission design. This component was initially designed with a Cu-Zn alloy and showed premature failure on synchronizer teeth during tests. To eliminate this problem several technical alternatives were analyzed considering the best cost and benefits ratio, defining to use the sintered steel FLC-4908 per MPIF Standard 35.

Abstract: High strength and high hardness can be readily attained after sintering when sinter-hardening grade powder metallurgy alloys are used. However, fast cooling rates greater than 60°C/min are usually required. This increases the cost of the sintering equipment and maintenance. To lower the required minimum cooling rate, the homogeneity of the alloying elements in the matrix and the hardenability of the material must be improved. Among the various popular alloying elements, nickel and carbon are the two most non-uniformly distributed elements due to their repelling effect. It is found that to improve their homogenization, the addition of Cr and Mo can alleviate the repelling effect between Ni and C. As a result, weak Ni-rich/C-lean ferrite and austenite are eliminated and replaced by hard bainite and martensite. A tensile strength of 1323 MPa and a hardness of 39 HRC are attained in sinter-hardened Fe-3Cr-0.5Mo-4Ni-0.5C compacts without any quenching treatment.