No abstract

No abstract

The violent nature of the electric discharge machining (EDM) process leads to a unique structure on the surface of a machined part. In this study, the influence of electrode material and type of dielectric liquid on the surface integrity of plastic mold steel samples is investigated. The results have shown that regardless of the tool electrode and the dielectric liquid, the white layer is formed on machined surfaces. This layer is composed of cementite (Fe 3 C) and martensite distributed in retained austenite matrix forming dendritic structures, due to rapid solidification of the molten metal, if carbon-based dielectric liquid is used. The intensity of cracking increases at high pulse durations and low pulse currents. Cracks on the EDM surfaces have been found to follow the pitting arrangements with closed loops and to cross perpendicularly with radial cracks and continue to propagate when another discharge takes place in the neighborhood. The amount of retained austenite phase and the intensity of microcracks have found to be much less in the white layer of the samples machined in de-ionized water dielectric liquid. The number of globule appendages attached to the surface increased when a carbon-based tool electrode material or a dielectric liquid was used during machining.

Hydroxyapatite (HA) is the major component of the natural hard tissues such as teeth and bone. It has been studied extensively as a candidate biomaterial for its use in prosthetic applications. However, the main weakness of this material lies in its poor mechanical strength which makes it unsuitable for load-bearing applications. On the other hand zirconia (ZrO2) powder has been widely studied because of its high strength and fracture toughness and good biocompatibility. Therefore, the addition of zirconia phase into HA will improve the mechanical properties and biocompatibility of HA ceramics. The present study focused on coating of HA-ZrO2 on commercially pure titanium (cp-Ti) using novel biomimetic sol-gel method. The HA-ZrO2 coatings produced with BSG method were exhibited highly crystalline and pure structure. The coating thickness of the samples was not significantly influenced by the change in gelatin concentration and volume. It was concluded that the suggested coating method is a useful method to produce a biomimetic coating layer on the cp-Ti sample surfaces.

No abstract