Powder Metallurgy of M2 High-Speed Steel for Rapid Tooling Applications

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Hu, Q.J.
Fuh, J.Y.H.
Wong, Y.S.
Lu, L.
Choy, C.M.
Chen, Z.D.

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A rapid tooling method has been developed to make a metallic tooling by powder metallurgy [1]. It is an integration of two techniques: rapid prototyping and powder metallurgy. The main advantages of this rapid tooling technique over the conventional techniques were short production cycle, low investment and manufacture costs. The experiment reported was on the density, microstructure, hardness and shrinkage of M2 high-speed steel parts. The process included de-binding, sintering and tempering of M2 high-speed steel powder. The material used was water atomised M2 high-speed steel powder and was sintered in the temperature range of 1270-1310°C for one hour. The process is typically a liquid phase sintering and enables to obtain high brown densities. After sintering, the micro-structure of the high-speed steel consisted of 6-12% carbides, 15-30 % austenite and 60-80% martensite, and the parts were to be tempered. With sintering at 1300°C and tempering, the results showed that 96% density was obtained, the typical hardness of Hv0.2510 (HRc50) was achieved, the horizontal shrinkage of the brown part was controlled at 15%±1% and the vertical shrinkage was at 14%±1%. Sintering above the temperature of 1300°C resulted in increasing of the brown density, rapid growth in grain size and deformation occurred. Based on the combination of density, shrinkage and hardness, the optimal sintering temperature and tempering procedure were determined.



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