Metal Injection Molded Titanium: Mechanical Properties of Debinded Powder and Sintered Metal
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JMEPEG https://doi.org/10.1007/s11665-020-04970-z
Metal Injection Molded Titanium: Mechanical Properties of Debinded Powder and Sintered Metal Suparat Bootchai, Nipon Taweejun, Anchalee Manonukul, and Chaosuan Kanchanomai (Submitted April 27, 2020; in revised form June 17, 2020) Metal injection molding (MIM) is a production technique to produce small and complex titanium part. During debinding, the elements of binder may react with titanium powders, form the interstitial elements and influence the mechanical properties of sintered part. Accordingly, the chemical composition and hardness properties of commercially pure titanium, which produced by metal injection molding process, were investigated and compared with wrought commercially pure titanium. Carbon and oxygen from binder were diffused into the titanium powder during the process of debinding, i.e., the contents of carbon and oxygen and the nanoindentation hardness at the edge of powder are higher than at center of powder. After sintering, the interstitial elements formed around the pores of sintered part, which caused the higher nanoindentation hardness than that of the matrix. The yield strength and the ultimate tensile strength of sintered part were also improved because of the interstitial elements. The findings can be applied for the production, usage and development of MIM titanium. Keywords
commercially pure titanium, composition, debinding, metal injection mold, nanoindentation
1. Introduction Metal injection molding (MIM) is an effective production technique that combines powder metallurgy with plastic injection molding technology. MIM can produce a near-net shape of small and complex metallic parts with low production cost (Ref 1, 2). Since titanium and its alloys have light weight, high strength and high fatigue resistance; they have been used in various applications, e.g., automotive, aviation, medical and dental devices (Ref 2-5). After the injection of feedstock (i.e., a mixture between metal powder and polymer binder) into a mold, the injected parts go through the debinding process to remove the binder from the injected parts. Two main debinding processes are generally available, i.e., thermal debinding and solvent debinding. Thermal debinding is performed under a temperaturecontrolled environment, while the solvent debinding is performed in solvent. For MIM process of titanium and its alloys, the thermal debinding is recommended (Ref 6) because it is an environmental-friendly process, and the sintering process can be consecutively performed using a single heating profile in the same furnace. The temperature and duration of debinding are usually more than 400 °C and more than 1h dwell time, depending on the geometry of component. Under the condition
Suparat Bootchai and Chaosuan Kanchanomai, Center of Materials Engineering and Performance, Department of Mechanical Engineering, Thammasat University, Pathumthani 12120, Thailand; Nipon Taweejun, Thai Tohken Thermo Co., Ltd, Chonburi 20160, Thailand; and Anchalee Manonukul, National Metal and Materi
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