Microstructure, wear, and corrosion characterization of high TiC content Inconel 625 matrix composites

Titanium carbide/Inconel 625 (nickel alloy) metal matrix composites (MMCs) are developed for the combination of the super mechanical and corrosion properties of nickel alloy matrix and the high hardness of reinforcing titanium carbide particles (TiCp). The microstructure, hardness, wear, and corrosion behavior of MMCs with different volume contents of TiC (25, 50 and 70 vol.%) were investigated. The effect of increasing TiC on the intermetallics and precipitates formed was examined using SEM/EDS and XRD analyses. The tribological behavior of the MMCs was investigated using wear testing with a pin-on-disk machine. The corrosion behavior was examined using potentiodynamic polarization experiments in 3% (w/v) NaCl solution. The results showed that the addition of TiC into the Inconel 625 alloy resulted in formation of several intermetallics such as MoNi4, Cr2Ni3 and MoCr, in addition to molybdenum and chromium carbides in the matrix alloy. A great improvement in the hardness was resulted with addition of 25 vol.% TiC and consequently the wear resistance was also improved. Further increase of TiC from 50 to 70 vol.% did not result in more improvement of both hardness and wear resistance. The corrosion resistance of TiC (25 vol.%) composite was comparable to that of monolithic Inconel 625 matrix alloy, while clear reduction in the corrosion resistance was found in the 50 and 70 vol.% composites. (C) 2018 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier Editora Ltda.