NOPR Collection:

Characterization of hydrophobic coating developed by micro arc oxidation on AA2014 alloy

Sun, 01 Oct 2017 00:00:00 GMT

Title: Characterization of hydrophobic coating developed by micro arc oxidation on AA2014 alloy Authors: Vishnoi, Mohit; Muthupandi, V; Murugan, S Senthil Abstract: The interest in aluminum alloys is on account of their attractive properties and high strength to weight ratio. In marine environments aluminum alloys especially AA2014, exhibit low corrosion resistance. Micro arc oxidation (MAO), a novel technique, has gained popularity for synthesizing ceramic coatings by electrochemical treatment using an aqueous electrolyte on aluminum, magnesium, titanium and their alloys and it can be a method of improving corrosion resistance of aluminum alloys. In this study, a stable film is produced on the substrate of AA2014 aluminum alloy by MAO in an aqueous electrolyte having chemically treated with myristic acid. Corrosion properties of these treated and untreated surfaces are evaluated in freshly prepared 3.5% NaCl solution by potentiodynamic polarization test. The electrochemical measurements showed that the MAO treatment significantly reduced the corrosion current densities (I_corr) and simultaneously enhanced the corrosion potential (E_corr) values indicating that the surface becomes nobler than the untreated one. The surface morphology of the coatings is characterized by scanning electron microscope (SEM). Hydrophobicity of these coatings is evaluated by means of contact angle measurement by goniometer. XRD test is also done on the sample to find out present elements on the coating. For one of the treated surfaces the static contact angle for water is measured to be approximately 129°. Thus the coatings are found to offer excellent corrosion resistance combined with hydrophobic property. Page(s): 325-330

Optimization of machining parameters on microdrilling of CFRP composites by Taguchi based desirability function analysis

Sun, 01 Oct 2017 00:00:00 GMT

Title: Optimization of machining parameters on microdrilling of CFRP composites by Taguchi based desirability function analysis Authors: Rajkumar, D; Ranjithkumar, P; Narayanan, C Sathiya Abstract: Microdrilling of CFRP composite materials is a complex process due to its properties and defects occur during the machining process. Optimization of process parameters is important to achieve the desired responses. This paper implies a new approach for optimizing the process parameters on drilling carbon fibre reinforced polymer (CFRP) composites. Optimization of process parameters is done by a method named as desirability function analysis (DFA), which is very useful tool to optimize multiple response problems. In microdrilling process, the feed rate and spindle speed and air pressure are selected as input parameter. Circularity and Feret’s diameter are taken as output parameters.The 0.5 mm solid carbide drill is chosen for microdrilling process. Analysis of variance (ANOVA) is adapted to investigate the performance characteristics of machining parameters. The confirmation tests are conducted to validate the test result.The analysis reveals out that hole quality is mostly influenced by air pressure. Page(s): 331-338

Multi-objective parametric optimization using the Grey-Taguchi approach for powder mixed electric discharge machining of grade-II titanium alloy with cryogenically treated electrodes

Sun, 01 Oct 2017 00:00:00 GMT

Title: Multi-objective parametric optimization using the Grey-Taguchi approach for powder mixed electric discharge machining of grade-II titanium alloy with cryogenically treated electrodes Authors: Kumar, Sanjeev; Singh, Rupinder; Batish, Ajay; Singh, T P Abstract: Electric discharge machining (EDM) is a widely accepted non-conventional machining process used for machining hard and difficult-to-machine materials by ordinary machining process. In the present work, powder mixed electric discharge machining (PMEDM) of titanium alloy (grade-II) with cryogenically treated electrodes was performed. In this paper, an attempt has been made to optimize the EDM process parameters of titanium work-piece using Grey-Taguchi approach. Experiments have been conducted under different conditions of pulse-on-time, peak current, electrode materials (copper, copper-chromium and copper-tungsten) and cryogenic treatment of electrode material. The machining characteristics such as metal removal rate (MRR), tool wear rate (TWR), surface roughness (SR) and micro-hardness (MH) are selected as the quality targets. Nine experimental runs based on L₉ orthogonal array of the Taguchi design of experiment are performed. An optimal parameter combination of the EDM was obtained through grey relational analysis (GRA). The analysis of variance (ANOVA) as applied to determine the level of significance of process parameters and it is found that peak current is the most significant factor for the machining of titanium. A confirmation experiment is performed to verify the optimum process parameter condition. Experimental results show that multi-response characteristics can be improved significantly through grey relational analysis. The validation experiment show an improved material removal rate of 5.2%, surface roughness of 4.92% and micro-hardness of 12.84% when Grey-Taguchi approach is used.Though, slightly increase of 2.95% in tool wear rate is observed. Page(s): 339-350

Influence of surface pretreatment on the coating quantity and properties of nanostructured octacalcium phosphate on commercially pure titanium

Sun, 01 Oct 2017 00:00:00 GMT

Title: Influence of surface pretreatment on the coating quantity and properties of nanostructured octacalcium phosphate on commercially pure titanium Authors: Suwanprateeb, Jintamai; Thammarakcharoen, Faungchat Abstract: The influence of surface pretreatment conditions including sodium hydroxide concentrations and cleaning methods on composition, microstructure and properties of the octacalcium phosphate (OCP) coating on commercially pure titanium by rapid biomimetic technique was studied.Layer of amorphous sodium trititanate (Na₂Ti₃O₇) gel was found to form on the surface of alkali pretreated titanium.Using high NaOH concentration and rinsed cleaning method could produce more uniform, but thinner OCP coatings than using low NaOH concentration and rigorous ultrasonic cleaning which resulted in isolated spheroidal microstructure.Regardless of pretreatment conditions, the contents of all OCP coatings were not significantly different and all coatings similarly comprised nano-thick and plate-like OCP crystals vertically grown on the surface of titanium.Contact angles of all coatings similarly decreased to zero compared to value of 76 for uncoated titanium indicating high wettability of all coating surfaces. Page(s): 351-361