Effect of nickel on sintering of self-propagating high-temperature synthesis produced titanium carbide
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Effect of nickel on sintering of self-propagating high-temperature synthesis produced titanium carbide S.K. Mishra (Pathak), S.K. Das, A.K. Ray, and P. Ramchandrarao National Metallurgical Laboratory, Jamshedpur-831 007, India (Received 30 June 1998; accepted 28 January 1999)
A detailed study of the sintering behavior of titanium carbide (TiC) powder synthesized by the self-propagating high-temperature synthesis (SHS) route was carried out with varying percentages of nickel. With an increase in the nickel content, porosity was found to increase along with Ni2.67Ti1.33 secondary phase at grain boundary. A 90–92% dense sintered body of TiC was produced from SHS-produced powder at 1800 °C with 10 wt% nickel.
I. INTRODUCTION
Increasing industrial needs for an efficient cutting of materials and better tool performance drive the development of newer tool materials, possessing higher wear resistance and toughness along with greater heat and oxidation resistance. Titanium carbide (TiC) is one such technologically important material for such applications. For an optimum performance a good sintered body of TiC is required. Conventionally prepared TiC powders generally require very high sintering temperatures in the range 2273– 2473 K to get a dense product. Very often hot pressing has also been used at 2073–2473 K temperatures. Selfpropagating high-temperature synthesis (SHS) characterized by energy efficient, fast, and purer product is an attractive method with several advantages over conventional processes.1–3 Also, owing to high exothermicity of the process, very high rates of self-heating and subsequent cooling of the reaction zone induce large concentrations of lattice defects and nonequilibrium structure in the product. Thus a more sinterable product can be obtained.4 Various binders such as Ni, Co, Fe, or alloy FeNi, Al2O3, etc., have been used to get a dense titanium carbide.5–7 In this article, a detailed study on the sintering behavior of the titanium carbide powder produced by the SHS technique with varying percentages of nickel is reported.
between 10 and 100 m. The powder was then mixed with nickel powder of ∼100-m size. The nickel concentrations were adjusted to be 10, 20, 30, and 40 wt%. TiC and Ni powders were mixed thoroughly with PVA as binder and were pressed into 15-mm diameter and 3-mm thick discs by using a load of 5 tons. These pellets were sintered at 1923 and 2073 K for 1 h in a graphite furnace in argon atmosphere and were subsequently furnace cooled. The microstructure of sintered samples was characterized by scanning electron microscope (JEOL 840 A), and detailed energy dispersive spectroscopy (EDS) analysis was carried out on the samples. The phase analysis was done through an x-ray diffraction patten recorded by a Siemens diffractometer. The densities of the samples were measured by the liquid (water) immersion technique using the Archimedes principle.
II. EXPERIMENTAL
Titanium carbide was synthesized from the commercial grade Ti (∼100 m) and
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