Carbide

About: Carbide is a research topic. Over the lifetime, 36331 publications have been published within this topic receiving 503586 citations.

Low-Temperature Elastic Properties of ZrC and TiC

Abstract: The elastic constants of zirconium carbide and titanium carbide were determined over the temperature range of 4.2° to 298°K using a pulsed‐ultrasonic phase comparison technique, and are compared to previously determined values for uranium carbide. Since these carbides are of the NaCl structure, only three independent constants are required to describe their elastic behavior. Their values at 298°K are ZrC0.94TiC0.91C114.720±0.0055.145±0.005C120.987±0.0051.060±0.002C441.593±0.0021.788±0.002 all in units of 1012 dyn/cm2. The differences in the elastic behavior of these group IV, transition metal carbides and the monocarbide of uranium are discussed in reference to their different electronic structure.

Chemical order in amorphous silicon carbide.

Abstract: While ordering in alloy crystals is well understood, short-range ordering in amorphous alloys remains controversial. Here, by studying computer-generated models of amorphous SiC, we show that there are two principal factors controlling the degree of chemical order in amorphous covalent alloys. One, the chemical preference for mixed bonds, is much the same in crystalline and amorphous materials. However, the other factor, the atomic size difference, is far less effective at driving ordering in amorphous material than in the crystal. As a result, the amorphous phase may show either strong ordering (as in GaAs), or weaker ordering (as in SiC), depending upon the relative importance of these two factors.

Surface integrity when machining age hardened Inconel 718 with coated carbide cutting tools

Abstract: Considerable attention has been given to the use of ceramic cutting tools for improving productivity in the machining of heat resistant super alloys (HRSA). However, because of their negative influence on the surface integrity, ceramic tools are generally avoided particularly for finishing applications. As a result the main high end manufacturers are more or less dependent on carbide cutting tools for finishing operations. Still the improper use of carbide cutting tools can also result in poor surface integrity. The objective of this investigation is to develop a set of guidelines, which will assist the selection of the appropriate cutting tools and conditions for generating favorable compressive residual stresses. This paper specifically deals with residual stresses and surface finish components of surface integrity when machining (facing) age hardened Inconel 718 using two grades of coated carbide cutting tools specifically developed for machining HRSAs. The cutting conditions were obtained from investigations based on optimum tool performance. The effect of insert shape, cutting edge preparation, type and nose radius on both residual stresses and surface finish was studied at this optimum cutting condition. This investigation, suggested that coated carbide cutting tool inserts of round shape, chamfered cutting edge preparation, negative type and small nose radius (0.8 mm) and coolant will generate primarily compressive residual stresses.

Tungsten carbides and W-C phase diagram

Abstract: The crystal structures of the tungsten monocarbide δ-WC and the disordered lower carbide β-W2C are studied. Using magnetic susceptibility measurements, the hexagonal carbide δ-WC is shown to be stable from 300 to 1200 K. The sequence of phase transformations associated with β-W2C ordering is analyzed. The temperature and composition stability limits of the cubic carbide γ-WC1−x are evaluated, and the first data are presented on the variation of its lattice parameter with composition. An optimized W-C phase diagram is proposed which takes into account detailed structural and phase-equilibrium data for tungsten carbides.

The influence of carbon nanotube (CNT) morphology and diameter on the processing and properties of CNT-reinforced aluminium composites

Abstract: Ball milling was used to disperse MWCNTs of two different morphologies (stiff and straight vs. bent and entangled) and diameters (very large diameter and 3.5 times smaller diameter) in aluminium powders, which were subsequently hot consolidated by hot extrusion. Characterization of the produced composites revealed that the CNT morphology plays an important role in affecting dispersion. It was found that the smaller diameter bent and entangled CNTs were more difficult to disperse with increase in CNT content compared to the larger diameter stiff and straight ones; which in turn affected the tensile properties and hardness of the composites. Furthermore, cold welding of the milled powders as well as carbide formation in the final composite was found to depend on the CNT diameter. The smaller diameter CNTs – having a larger effective interfacial contact area with the aluminium matrix compared to the larger ones for a given CNT wt.% – were found to reduce particle welding during milling and to be more affected by carbide formation. Nano-sized particles of aluminium oxide as well as nano-rods of aluminium carbide, in addition to CNT damage were observed upon TEM analysis of the smaller diameter CNTs.