Crystal structure analysis of M2 high speed steel parts produced by selective laser melting

M2 high speed steel (HSS) samples were produced by an additive manufacturing (AM) process, selective laser melting (SLM). The observed microstructure from SEM and FIB was characterised by a continuous and homogeneous network of dendrites within two different phases. These phases were characterised to be bcc single crystals and fcc/bcc polycrystals from TEM-SADP. EBSD results also indicated that the bcc grains were randomly orientated. In addition, the lattice constants from two different SADPs of bcc crystal were calculated to be 2.892 Å and 2.905 Å, larger than high purity iron bcc structure of lattice constant 2.867 Å. The elements V, Cr, Mo, W and Si were detected in the iron matrix with TEM-EDS. These elements were responsible for the enlargement of the lattice constant. TEM-EDS results also indicated that the network of dendrites were carbides. These results gave insights on the rapid solidification phenomenon in SLM.