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Electrochemical machining is applied not only in die and mold fabrication, but also in the finishing process for parts manufacturing. Especially when ECM is used in finishing purposes, surface properties become more important. In this study, the wettability which is one of the surface properties was focused on and discussed. The sessile drop method and the contact angle are used to evaluate the wettability. In order to measure the contact angle based on JIS R 3257, how the contact angle changes within the allowable measurement range that JIS prescribed was experimentally examined. It was found that the contact angle changes temporally and quantitatively within the JIS allowable extent. In order to measure contact angles correctly, the measurement conditions under which the range is stricter than the JIS range was investigated and discussed. After the measurement conditions were decided, contact angles of stainless SUS304 surfaces that machined with ECM were experimentally investigated. In order to clarify the relationship between ECM conditions and the wettability of the machined surface, the change in the contact angle when varying the kind of electrolyte and the current density was examined. It was found that the surfaces machined with ECM using NaNO 3 solution as electrolyte with lower current density has a lower contact angle. When the current density increases, there appears proportional relation between the current density and the contact angle. [ABSTRACT FROM AUTHOR]

The dynamics of a receding contact line of water drops on polymeric substrates (poly(methyl methacrylate), PMMA, and polycarbonate, PC) was studied using the sessile drop method. For smoother substrates, multiple stages were observed: the constant contact radius (CCR) mode, the constant contact angle (CCA) mode, and the mixed mode. In the CCA mode, the contact angle (CA) remained nearly constant and the receding dynamic CA could be identified. The relation between the receding dynamic CA and the withdrawal rate was experimentally determined, and the receding dynamic CA was found to decrease with increasing liquid withdrawal rate. A decrease of 5–10° was found for PMMA substrates, whereas a decrease of 10–20° was observed for PC substrates for commonly applied liquid withdrawal rates. Our results quantitatively agree with those obtained by the capillary tube method and the plate method, and we demonstrated that the sessile drop method can serve as an alternative method for studying contact line dynamics. In addition, for the rough PC substrates, the CCA mode was absent and the receding dynamic CA could not be identified. Therefore, we demonstrated that on rough polymeric substrates, the sessile drop method must be used with caution, and complete CA relaxation profiles and liquid withdrawal rates should be reported. [ABSTRACT FROM AUTHOR]

Surface Free Energy (SFE) of solids should be calculated using theoretical models. The contact angle (CA) measurement on a surface is considered the most practical way to obtain the SFE. The results of five methods based in the models are compared: the method of Zisman (ZI), the geometric mean (GM), the harmonic mean (HM), the Lifshitz-van der Waals/ Acid-Base (LW/AB) and the equation of state (ES). The SFE calculated with GM, HM and LW/AB methods change with the amount and type of liquid used, however, when water, glycerol and dimethyl sulfoxide are used together the SFE and its dispersive and polar components are similar in value for the three methods. In the case of the ES model the values of SFE change with the liquid used; finally using the ZI method the SFE values are 20% lower than the values of SFE obtained with the other methods. [ABSTRACT FROM AUTHOR]

The sessile drop method is an easy and fast method used to measure the contact angle between solids and liquids. The value of the contact angle is used in surface characterization, in particular the wettability of solid surfaces by the liquid and to calculate the surface free energy. In this work, we study the effects of the volume of the drop placed on the surface, the elapsed time between drop placing and measurement and the cleaning of the substrate (not cleaning, washed with ethanol or washed with acetone) in the value of the contact angle on Ti6Al4 V and AISI 316 stainless steel. We found that drop asymmetry is a very important parameter that must be considered in CA measurements. Anasymmetry parameter used to qualify the drop asymmetry is proposed. It was also found that the degree of cleanliness produces dispersion in the contact angle values; on the other hand no differences were found between cleaning with ethanol or acetone. CA decreases with time and increases slightly with decreasing droplet volume. [ABSTRACT FROM AUTHOR]

Abstract: The density of liquid NiCoAlMo quaternary alloy with a fixed molar ratio of Ni:Co:Al (x Ni:x Co:x Al≈73:12:15) which is close to the average value of the commercial Ni-based superalloys TMS75, INCO713, CM247LC and CMSX-4, and molybdenum concentration change from 0% to 10% (mass fraction) was measured by a modified sessile drop method. It is found that the density of the liquid NiCoAlMo quaternary alloy decreases with increasing of temperature, but increases with the increase of molybdenum concentration in the alloys. The molar volume of liquid NiCoAlMo quaternary alloy increases with the increase of temperature and molybdenum concentration, and shows a negative deviation from the ideal linear mixing. The liquid density of NiCoAlMo quaternary alloy calculated from the partial molar volumes of nickel, cobalt, aluminum and molybdenum in the corresponding Ni-bases binary alloy are in good agreement with the experimental results; it means that within the error tolerance range the density of liquid Ni-based multi-component alloys can be predicted from the partial volumes of elements in Ni-based binary alloys in liquid state. [Copyright &y& Elsevier]

Abstract: The densities of four kinds of molten Ni-based commercial alloys were measured with a modified sessile drop method, and calculated using the calculating software. It is found that the densities of the molten Ni-based commercial alloys decrease and their molar volume increase with increasing of temperature. Compared with the ideal mixing, the molar volumes of the molten Ni-based commercial alloys show negative deviations. It can be attributed to an accommodation between various atoms in the alloys. [Copyright &y& Elsevier]

The phenomena influencing the properties of plasma sprayed ceramic-metal composite (cermet) deposits were examined. For that purpose, cermet deposits were developed by co-spraying alumina and austenitic stainless steel powders and were compared with those fabricated by spraying these powders individually. A set of particle injection and plasma spray parameters were determined by optimizing deposition efficiency of sprayed powders. The properties of the fabricated composite deposits were only partially dependent on the inherent properties of the parent materials and other factors had more dominating influence. Beside other factors, in-flight metallic particle oxidation and ceramic-metal wetting behavior were found to be the major phenomena controlling deposit properties. The in-flight particle oxidation, contributing up to 43% of the total oxide in metallic deposits, resulted in higher hardness and elastic modulus values of stainless steel deposits. The formed oxide could assist in improving the wetting behavior of stainless steel-alumina system, studied by sessile drop method. In non-wetting conditions, extensively fragmented stainless steel splats were collected on predeposited alumina causing poor interlamellar contacts and inferior deposit integrity and mechanical properties. [ABSTRACT FROM AUTHOR]