Microstructure Evolution of Laser Direct Metal Deposition of M2 High Speed Steel

Publisher: Trans Tech Publications

E-ISSN: 1662-9752|2016|879|2198-2203

ISSN: 0255-5476

Source: Materials Science Forum, Vol.2016, Iss.879, 2017-02, pp. : 2198-2203

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Abstract

In the current investigation, the M2 high speed steel (HSS) sample was produced by laser direct metal deposition (DMD) with a rapid manufacturing (AM) process. The overall microstructure analysed by light optical microscopy (LOM) was a gradual transition from bottom zone to top zone due to the continuous decrease of the cooling rate. The observed microstructure from SEM and XRD was consisted of a cellular or dendritic structure of ferrite, martensite, retained austenite and fine carbides. Annealing at 860 oC led to spheroidization of carbides. The carbides were examined by XRD to be M6C and MC. With prolonging the annealing holding time, the more homogenous microstructure could be acquired. These studies demonstrated that annealing can improve microstructures of M2 HSS produced by DMD.