Microstructural characterization and wear behavior of (Fe,Ni)-TiC MMC prepared by DMLS

Direct metal laser sintering (DMLS) is an evolving technique for the production of parts with complex geometry and unique microstructure, implemented in tooling applications by manufacturing of tool inserts. In the present investigation, microstructure, phase composition, mechanical and tribological properties of (Fe,Ni)-TiC composites prepared by DMLS were investigated. Thermal cracking during sintering was observed, which degraded the produced parts, influenced by porosity and particular spherical particles. Dissolution of TiC led to subsequent FCC to BCC matrix phase transformation and to an increase of the average coefficient of thermal expansion. Therefore, a combination of high TiC amount, loss of low-CTE properties of the matrix and matrix phase transformation led to cracking of the composites. Decrease of TiC content to 30wt.% led to a crack-free, but 10% porous specimen. Bending strength, hardness and wear resistance in sliding wear of the crack free specimen were found in the lower range of conventionally manufactured hard metals due to porosity, low TiC amount and low matrix hardness. (c) 2005 Elsevier B.V. All rights reserved.