Research Output
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PublicationElectrical discharge coating of NiTi alloy in deionized water( 2021-01-01)Shape memory alloys, specifically nickel-titanium (NiTi), exhibit excellent technical properties that suited them for biomedical applications. However, the release of nickel ions into human body is a drawback because it results in severe adverse health effects as well as degrades the biocompatibility of the alloys. In this work, surface modification through adaptation of electrical discharge machining was used to develop a deposition layer of titanium oxide on NiTi alloy surface. The adaptation was through electrical discharge coatings (EDC) parameters such as polarity, gap voltage, and erosion depth that were set up to study their effects on the experimental performance. The experiment was parameterized by implementing 2 level of full factorial design with ANOVA analysis to measure the surface roughness of that machined surface. One-factor-at-a-time, OFAT method is applied for XRD analysis by adopting the previous parameters approach. The EDC process was aided with deionized water and pure titanium rod as the dielectric fluids and electrodes, respectively. It was determined that the high level of gap voltage provided some major constituents on the surface of NiTi alloy based on XRD analysis. As apparent, this substantiated the presence of the tool materials and their oxide layer phases. The interaction of polarity and gap voltage also indicated a significant effect towards the surface roughness.
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PublicationSurface roughness analysis of NiTi alloy in electrical discharge coating process( 2020-12-18)Nickel-Titanium (NiTi) alloys, most widely known as nitinol, are presently employed in many micro-engineering applications such as coronary stents of medical implants due to their unique properties (shape memory effect and superelasticity). However, non-optimized surface finishing attributed a significantly high potential of nickel exposure after a long time of application. Releasing of nickel ion to the body environment can be harmful and toxicity resulting in adverse health as well as degrading the material biocompatibility. It is widely known that controlled surface roughness play a vital role in the formation of new bone ingrowths around implant. In this study, surface modification of NiTi alloy was used through electrical discharge coating (EDC); an adaptation of electrical discharge machining. The potential of EDC in which can facilitates the production of hard coatings may exploit the phenomena for the attachment of desirable materials onto the surface of materials. Therefore, the aim of this paper is to present a robust method (two levels of full factorial design and ANOVA) to determine the desired parameters and significant factors based on the surface roughness of the machined surface. Manipulation of parameters set up such as gap voltage, discharge duration and pulse interval and the current were employed and a reverse polarity was selected for this experiment. The results demonstrated that the most significant factors influence the surface coating performances are the discharge duration, current, gap voltage as well as the interaction between gap voltage and discharge duration.
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PublicationThe Effect of Parameters of Electrical Discharge Coatings on the Tool Electrode Erosion and Maximum Height Roughness on NiTi Alloy( 2021-01-01)This paper presents the influence of electrical discharge coatings parameters on the material loss due to the tool electrode erosion (MLTE) and the maximum height roughness, Rz on the NiTi alloy substrate. Five parameters were investigated; namely polarity, discharge duration, peak current, pulse interval and gap voltage. The experimental study was carried out using 2-level factorial design and analyzed using analysis of variance (ANOVA). The analysis results showed that the discharge duration dominates the effect on MLTE and Rz up to 39.39 and 72.41%, respectively. Then, this followed by the peak current at 15.52 and 4.63%, respectively. Furthermore, several interactions between discharge duration with other parameters were also significant on the model for both responses. Higher MLTE and Rz were recorded during high discharge duration and peak current due to the impact of increasing the discharge energy.
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PublicationEvaluation of thickness variation of recast layer formation on nitinol from electrical discharge coatings process( 2020-06-17)Nitinol is an intermetallic alloy with outstanding properties that suitable as biomaterial. This alloy is capable of recovering to its initial shape after external loading through transformation of the crystalline structure. Unfortunately, excessive exposure of nickel element from this alloy is harmful to human body if released. Thus in this study, the alloy surface was deposited with an oxide layer via electrical discharge coating (EDC) process. The process was performed in deionized water and pure titanium as the electrode. The variation thickness of the recast layer formation was examined by analysing the effects of polarity, gap voltage and erosion depth. Single crater images and electrical waveforms were captured and utilised to elucidate the aforementioned effects. The results exhibited a significant change of layer thickness variation due to different polarity conditions. It was also confirmed that the single crater formation at different polarity was influenced by discharge energy. On other hand, the increase in the open gap voltage can expand the recast layer thickness in lower variation of reverse polarity condition. Finally, erosion depth attributed to a constant layer thickness but in low thickness variation when reverse polarity was employed.