Effect of Coating and Low Viscosity Oils on Piston Ring Friction under Mixed Regime of Lubrication through Analytical Modelling

This paper presents the impact of coating topography in piston ring-liner conjunction under mixed regime of lubrication using low viscosity oils. The study provides a time efficient analytical model including mixed-hydrodynamics regime of lubrication under different contact conditions. The method modified the expressions of the contact load and area of Greenwood-Tripp model in order to capture the real asperities interaction into contact. The model represents the tribological behavior of a thin top ring at Top Dead Centre, where boundary and mixed conditions are predominant. Electroplated CrN and PVD TiN coated rings were studied to predict the ring friction. The results are compared with an uncoated steel ring. The CrN coating shows slighter coefficient of friction, due to the coating morphology and roughness parameters. The TiN coating presents thicker lubricant films and higher coefficient of friction because the surface topography is quite rough with high peaks. This can be explained because of the major contribution of the roughness parameter and asperity slope in the boundary friction prediction.

Influence of current density and temperature in the zinc electroplating process at sulfate-based acid solution: study on process efficiency and coating morphology

Zinc as a metallic coating is a common strategy to protect the carbon steel against corrosion. The most common process of zinc deposition is known as electroplating. Because of the high toxicity of cyanide-based baths, the interest in acid baths has grown, but they present many challenges to be overcome. Several operational parameters and bath constitution – such as current density, pH, and zinc concentration – can impact the current efficiency, deposit quality, and coating morphology. In this work, the process efficiency and the coating morphology were evaluated on electroplated AISI 1008 carbon steel samples. The current density and temperature were individually varied on a range from 7.5 mA.cm-2 to 30.5 mA.cm-2, and from 40 °C to 60 °C, respectively. The process efficiency was evaluated by current efficiency (eC). The surface morphology was analyzed by both optical microscopy (OM) and scanning electron microscopy (SEM). Varying the bath temperature did not promote impacts in the current efficiency, which remained in all temperatures evaluated over 95%. On the other hand, increasing the current density, increased the current efficiency, starting from (85 ± 2)% at 7.5 mA.cm-2 to (92 ± 2)% at 19.0 mA.cm-2, and (95 ± 1)% at 30.5 mA.cm-2. Through OM and SEM analysis, the increase in the temperature tended to turn the coating rougher, and the sample was not completely covered at 7.5 mA.cm-2. Therefore, we recommend the use of a temperature between 40 °C and 50 °C associated with a current density of 30.5 mA.cm-2.

The Microstructure and Properties of Carbon Thin Films on Nanobainitic Steel

The aim of this study was to assess whether it is possible to produce a high adhesive carbon coating by applying low-temperature RFCVD and glow discharge methods on nanobainitic X37CrMoV5-1 steel with and without nitrided sublayer. For this purpose, several methods of investigation were used: observations of coating morphology by scanning electron microscopy (SEM), analysis of bonds found in coatings (Raman spectroscopy), microhardness tests and adhesion of coatings (Scratch tests). Our research has shown that low-temperature RFCVD and glow discharge processes of nanobainitic X37CrMoV5-1 steel allow producing carbon coatings that can be described as hardened carbon coatings with very high hardness—> 2000 HV 0.25 in case of RFCVD processes and > 3300 HV 0.025 for glow discharge process and low friction coefficient—near 0.12 at 5 N load. However, the adhesion of produced coatings to the steel substrate strongly depends on the appropriate selection of the process parameters and on the proper preparation of the substrate before the deposition regarding the thermal stability of nanobainite.

Ultrasonically assisted macrocyclic ring compound coatings for corrosion protection of copper in 3.5% NaCl solution

ABSTRACT: Macrocyclic ring compounds are potential corrosion inhibitors due to their high planarity, rigidity, and presence of many heteroatoms such as nitrogen, oxygen, phosphorus, and sulfur. However, their application as corrosion inhibitors has been faced with a challenge of insolubility in most organic and aqueous solvents. To overcome this challenge and to harness the untapped hydrophobic property of these compounds, this research, via ultrasonication method dispersed a macrocyclic ring compound known as free-based Phthalocyanine (Pc) to fabricate a corrosion-resistant coating on the Cu surface. The Cu samples were coated through a 24 h immersion by self-assembly method in different systems of sonicated and non-sonicated solutions of the compound in dimethyl sulfoxide (DMSO). The effect of sonication and immersion duration on the coating morphology, compactness, and consequent corrosion inhibition was analyzed. Electrochemical and surface imaging techniques revealed higher corrosion protection in 3.5% NaCl for the Pc coated Cu samples after sonication compared to the non-sonicated systems.

Characterization of Phosphate Coatings: Influence of the Acid Pickling Conditions

This research emphasizes the importance of the acid cleaning prior to the phosphate development on high-strength steel rods. It compares the phosphate properties achieved after different acid-pickling conditions. The most common inorganic acids were considered in this study. Additionally, taking into account the environmental and safety concerns of these acids, the assessment of a less harmful organic acid is presented. This study revealed significant differences in the coating morphology and chemical composition whereas no great changes were found in terms of the coating weight or porosity. Thus, hydrochloric and sulfuric acid promote the growth of a Fe-enriched phosphate layer with a less conductive character that is not developed after the pickling with phosphoric acid. The phosphate developed after the citric acid pickling is comparable to that developed after the inorganic acids although with a porosity slightly higher. The temperature of the citric acid bath is an important parameter that affects to the phosphate appearance, composition, and porosity.

Self-Healing Properties of Cerium-Modified Molybdate Conversion Coating on Steel

Environmentally friendly alternatives to chromium—phosphate/molybdate and cerium-modified phosphate/molybdate conversion coatings—were deposited on a carbon steel surface. Different surface analytic techniques were applied to obtain complementary information on the composition, element distribution morphology and inner structure of the coatings in order to establish the relationship between coating properties and corrosion performance. The higher protective and stronger self-healing abilities were found for phosphate/molybdate/cerium conversion coating deposited in a sulphate-containing solution. The protective barrier strength was found to be related with certain aspects of the coating morphology such like homogeneous distribution of fine crystallites and, hence, lower number of structural defects. The self-healing ability depended on both, the composition (higher amount of Ce(IV)) and micro-structural characteristics, such as defectiveness, of the conversion layer.

Optimisation of Design and Manufacturing Parameters of 3D Printed Solid Microneedles for Improved Strength, Sharpness, and Drug Delivery

3D printing has emerged as a powerful manufacturing technology and has attracted significant attention for the fabrication of microneedle (MN)-mediated transdermal systems. In this work, we describe an optimisation strategy for 3D-printed MNs, ranging from the design to the drug delivery stage. The key relationships between design and manufacturing parameters and quality and performance are systematically explored. The printing and post-printing set parameters were found to influence quality and material mechanical properties, respectively. It was demonstrated that the MN geometry affected piercing behaviour, fracture, and coating morphology. The delivery of insulin in porcine skin by inkjet-coated MNs was shown to be influenced by MN design.