Fabrication of graphite reinforced TiCxNy by spark plasma sintering technique: A comparative assessment of microstructural integrity and nanoindentation properties. (May 2021)

• Record Type: Journal Article
• Authors: Mekgwe, Gadifele Nicolene; Akinribide, Ojo Jeremiah; Akinwamide, Samuel Olukayode; Olubambi, Peter Apata
• Is Part Of: Vacuum. Volume 187(2021)
• Publication Date: 2021-05
• Subjects: TiCN -- Graphite -- Spark plasma sintering -- Morphology -- Microstructure; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2021.110144
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: This study investigated the fabrication of three different binderless TiCx Ny (where the values of x and y are 0.5, 0.7, 0.9 and 0.5, 0.3, 0.1 respectively) reinforced with 0.5 wt%, 1.0 wt%, and 1.5 wt% graphites. The reinforcement particles were dispersed in TiCN matrix using the high energy ball milling technique, and the admixed powders were sintered using the novel spark plasma sintering method. The phase analysis and the structural morphologies of the starting powders and sintered specimens were analyzed using field emission scanning electron microscope (FE-SEM), Transmission electron microscope (TEM), and X-ray diffractometer (XRD), respectively. The milling process outcomes showed that the composite powders contain some isolated graphite powders distributed around the matrix as titanium carbonitride. The stoichiometry of the processed powders gave some consistency in the carbon-rich phase. The significant improvement in the properties of as-sintered composites, including microstructure, elastic modulus, fracture toughness, and hardness, was due to the presence of graphite in the ceramic composite. The graphite were also observed to improve the relative densities of specimens as the optimum relative density was achieved at 99.56% when 1.5 wt% of graphite was dispersed in TiC0.9 N0.1 . The nanohardness and elastic modulus values of the most improved composites are as follow; From the nanohardness test, the composites with 0.5 wt% graphite + TiC0.5 N0.5, 1.5 wt% graphite + TiC0.7 N0.3 and 1.0 wt% graphite + TiC0.9 N0.1 had their nanohardness values recorded as 34.5 GPa, 33.3, and 35.1 GPa, respectively, while the highest elastic modulus of 350 GPa was recorded in TiC0.5 N0.5 and TiC0.7 N0.3 with respective reinforcement addition of 0.5 and 1.5 wt% graphite respectively. There is a clear increase in grain growth and graphite segregation when 1.5 wt% of graphite was dispersed in TiC0.9 N0.1 . However, the uniform distribution of grains was observed when the same (1.5 wt% graphite) proportion of nanoparticle was dispersed in TiC0.5 N0.5 and TiC0.7 N0.3 composites. Highlights: Microstructures and mechanical behaviour of TiCx Ny (where x = 0.5, 0.7 and 0.9; y = 0.5, 0.3 and 0.1) composites. Complete diffusion of graphite into titanium nitride occur at sintering temperature of 2100 °C to form fcc-TiCN phase. The sample preparation was carried out to highlight the impact of powder properties and performance in sintering. Sub-micron sizes of each powder were determined using SEM and XRD analysis. Both the rim and core phases in the structure show uniform phases with similar patterns of diffractions.