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Development of binderless ultra-tough titanium carbonitride (TiCN) using spark plasma sintering technique

  • Authors: Akinribide, Ojo Jeremiah
  • Date: 2019
  • Subjects: Titanium , Sintering , Nanoparticles
  • Language: English
  • Type: Doctoral (Thesis)
  • Identifier: http://hdl.handle.net/10210/443738 , uj:38757
  • Description: Abstract: Binderless ultra–tough titanium carbonitride (TiCN) was successfully consolidated by spark plasma sintering. The impact of blending and milling parameters on the formation of titanium carbonitride from milled titanium nitride, graphite and multiwalled carbon nanotube (MWCNTs) admixture were investigated. The effect of wet milling and dry milling on the phases and morphology of the developed composites were also studied. The morphology, microstructure and the chemical composition of as – received powders, admilled powders and the sintered compact were characterized by using energy dispersive Xray spectroscopy (EDS), X-ray diffractometer, and scanning electron microscopy respectively. The varying compositions of the ad-milled powders were sintered at 100 oC/min (heating rate), 10 mins (holding time), 50 MPa sintering pressure and 2000 oC (sintering temperature). Vickers hardness test, fracture toughness and modulus of elasticity were carried out on the sintered sample to evaluate the mechanical properties. The sintered TiN-based composites were completely formed without cracks, however with very fewer pores, an indication of a good metallurgical bonding quality achieved at the composite grain boundary interface. The structure of the grains has completely transformed to bimodal grains within the composites at 1 wt.% graphite in TiN for 40 h of milling, and subsequent composites developed was based on the result obtained at 1 wt.% graphite in TiN for 24 and 40 h of milling at different compositions. Much increment was observed in microindentation hardness and fracture toughness values of the sintered compact as the percentage graphite increased. The results show that grain size of the sintered sample decreases as the percentage composition of graphite/MWCNTs particles and milling time increases. Based on the results of the analysis, it was concluded that the incorporation of graphite/MWCNTs enhances the microstructures which ultimately are crucial to the mechanical behaviour of the sintered compacts. , D.Phil. (Metallurgical Engineering)
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Effect of built orientation on direct metal laser sintering of Ti-6Al-4V

Sintering of nanostructured titanium carbonitride from carbonitrothermic reduced ilmenite

  • Authors: Mojisola, Tajudeen
  • Date: 2019
  • Subjects: Sintering , Nanostructured materials , Titanium , Nitrides , Ilmenite
  • Language: English
  • Type: Doctoral (Thesis)
  • Identifier: http://hdl.handle.net/10210/418221 , uj:35451
  • Description: Abstract: In recent years, there has been concerted effort towards the synthesis of cermet materials from low grade titanium ore. This is because the reserve of high grade titanium containing ore, i.e. natural rutile, is fast depleting and rutile becoming more expensive across the globe. Today, titanium containing hard ceramic powders, e.g. TiC, TiN and their solid solution TiCN powders have become important reinforcement materials due to their suitable properties. Titanium carbonitride, which is a boundary solid solution of titanium carbide and titanium nitride combines the excellent properties of both TiC and TiN in one structure of TiCN. In order to make this special material readily available, various methods have been adopted to synthesize titanium carbonitride powder. Although, the synthesis of titanium carbonitride by carbothermic reduction of titanium dioxide (rutile) with carbon under nitrogen atmosphere has been the most widely used for the commercial production of titanium carbonitride. However, this process requires the extraction and purification of titanium dioxide from its ore e.g. ilmenite, which itself is a costly process, or the use of natural rutile, which is fast depleting and becoming more expensive across the globe. Ilmenite (FeTiO3), which is a mineral source of titanium dioxide, is abundantly found in many parts of the world, most especially in South Africa. South Africa, is a leading producer of ilmenite in the world, accounting for about 37% of 6.2 million metric tons of the global production. Hence sourcing and processing of TiCN powder directly from South African ilmenite will be an added advantage. It is on this premises that the urgency for the processing of South African ilmenite to its final products, e.g. titanium containing hard ceramic products, such as TiC, TiN and/or TiCN powders or composite, and titanium metal, is being hung. Hence, this study develops a mechano-chemical processing route for the synthesis of titanium containing hard ceramic powders from ilmenite concentrate, which could be used for the production of cutting tools made of TiC and TiCN composite materials. The study also determines the possibility of sintering bulk TiCN based cermets with different metal matrices. For the synthesis of titanium carbide and titanium nitride/carbonitride powders, mixtures of ilmenite concentrate and graphite were milled in a planetary ball mill (PM 100) for different time intervals of 0, 30, 60 and 120 min, and carbo(nitro)thermally reduced under argon and nitrogen gas in a high temperature laboratory furnace (Thermal Tech., USA), respectively. These carbo(nitro)thermic reductions of mixtures of ilmenite concentrate and graphite result in the formation of Fe –TiC and Fe – TiCN powder composites in which globules of TiC and TiCN particles are embedded in the iron matrix,.. , Ph.D. (Engineering Metallurgy)
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Effect of build direction on the microhardness and dry sliding wear behaviour of laser additive manufactured Ti-6Al-4V

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