Combined strengthening of multi-phase and graded interface in laser additive manufactured TiC/Inconel 718 composites

Laser metal deposition (LMD) additive manufacturing of TiC particle reinforced Inconel 718 composite parts was performed. The influence of laser energy density (LED) on densification, microstructures and wear behaviour of LMD-processed composites was studied. It showed that using a LED of 280 J mm-3 produced ∼5% porosity in LMD-processed composites, caused by the aggregation of reinforcing particles. A further increase in LED above 350 J mm-3 yielded near-full densification. Two categories of reinforcing phases, i.e. the substoichiometric TiCx particles and the in situ (Ti,M)C (M = Mo, Nb and Cr) carbide having 7-10 at% Nb and Mo contents, were formed in the matrix of LMD-processed composites. The TiCx reinforcing particles changed from an irregular poly-angular shape to a smoothened and refined structure as the LED increased. An increase in LED resulted in a larger amount of phase formation and an enhanced degree of crystal growth of the in situ (Ti,M)C reinforcement. The interfacial graded layer with thickness of 0.2-1.2 μm, which was identified as (Ti,M)C (M = Mo, Nb and Cr) carbide with 5-6 at% Mo and Nb contents, was tailored between the TiC x particles and the matrix. At an optimal LED of 420 J mm -3, a considerably low coefficient of friction of 0.38 and resultant low wear rate of 1.8 × 10-4 mm3 N-1 m-1 were obtained in sliding tests, due to the combined strengthening of the interfacial graded layer and the multiple reinforcing phases. The wear resistance decreased at an excessive LED because of the coarsening of reinforcement crystals and the decrease in microstructural uniformity of composites.

Subjects

additive manufacturing

graded interface

laser metal deposition (LMD)

metal matrix composites (MMCs)

particle reinforcement

DDC Class

530: Physik

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Combined strengthening of multi-phase and graded interface in laser additive manufactured TiC/Inconel 718 composites