Investigation of material removal mechanisms in EDM of composite ceramic materials

Since the introduction of glass fiber-reinforced polymer composites in the early 1940s, composite materials development was driven by the needs of space, defense, and aircraft industries w...

Machining of fiber-reinforced composites

Graphene nanoplatelet/silicon nitride composites with high electrical conductivity

Electric discharge machining (EDM) has achieved remarkable success in the manufacture of conductive ceramic materials for the modern metal industry. Mathematical models are proposed for the modeling and analysis of the effects of machining parameters on the performance characteristics in the EDM process of Al2O3+TiC mixed ceramic which are developed using the response surface methodology (RSM) to explain the influences of four machining parameters (the discharge current, pulse on time, duty factor and open discharge voltage) on the performance characteristics of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR). The experiment plan adopts the centered central composite design (CCD). The separable influence of individual machining parameters and the interaction between these parameters are also investigated by using analysis of variance (ANOVA). This study highlights the development of mathematical models for investigating the influences of machining parameters on performance characteristics and the proposed mathematical models in this study have proven to fit and predict values of performance characteristics close to those readings recorded experimentally with a 95% confidence interval. Results show that the main two significant factors on the value of the material removal rate (MRR) are the discharge current and the duty factor. The discharge current and the pulse on time also have statistical significance on both the value of the electrode wear ratio (EWR) and the surface roughness (SR).

Modeling and analysis of the effects of machining parameters on the performance characteristics in the EDM process of Al2O3+TiC mixed ceramic.

In an attempt to optimize the structure and properties of silicon nitride ceramics, a variety of novel processing techniques and materials compositions have evolved over the last 15 years. Among the most important, was the development of various silicon nitride-based composites. A review of particulate, silicon nitride-based composites other than whisker- or platelets-reinforced, is presented. Materials based on silicon nitride and SiAlONs, with additions of carbides, nitrides and borides of transition metals are described. Special emphasis is placed on TiN- and TiC-containing ceramics. The manufacture of composites by hot pressing, reaction sintering, pressureless and gas-pressure sintering is discussed. The data on properties, including conductivity, density, Young's modulus, strength, fracture toughness, hardness, thermal expansion, wear, creep and oxidation resistance are presented. Analysis of actual and potential uses of the selected composites demonstrates that the particulate composites are very promising as tool, structural and electronic materials.

Particulate silicon nitride-based composites

The recent improvements in mechanical properties of ceramics have led to the development of high-strength and high-toughness ceramic composites the machining of which, using conventional techniques, is a rather complicated and expensive routine especially when complex parts are manufactured. Electrical discharge machining is an attractive alternative machining technique but it requires electrically conductive ceramic materials. New conductive silicon nitride- and alumina-based composites with good mechanical properties were developed for this purpose by adding amounts of TiC and/or TiN particles to the ceramic matrix. The machinability and the physical properties of the composites are related to the content and the characteristics of the conductive TiC and/or TiN particles. The compositions can be adjusted to find the best compromise between high strength and electrical discharge machinability.

B. Cales

Papers

Electrical discharge machinable ceramic composites