Preparation of tin coating on the surface of copper-coated carbon fiber and its effect on the microstructures and properties of the composite coating

In order to prevent the copper coating on the carbon fiber surface from oxidizing and falling off, the tin coating is plated on the surface of copper-coated carbon fiber. In this paper, the copper-tin composite coating with different thicknesses of tin coatings were successfully prepared by electroless plating. The results show that with the increasing of electroless tin plating time, the thickness of the copper-tin composite coating increases. The test results of the bonding force between the composite coating and the carbon fiber show that the coating bonding force is the best when the thickness of composite coating is between 1.31 μm and 1.55 μm. This is due to the formation of copper-tin intermetallic compounds preventes direct contact between the copper coating and oxygen, which can effectively inhibit the oxidation of the copper plating layer, thereby making the plating layer less likely to fall off. However, the excessively thick tin coating would increase the internal stress of the coating, and promote the generation of cracks on the surface of the composite coating, which would cause the composite coating to fall off. This research will provide new ideas for the preparation of high-performance copper plating on the surface of carbon fiber, and provide an important theoretical and practical basis for the application of copper coatings.

Effect of the Shape of Rolling Passes and the Temperature on the Corrosion Protection of the Mg/Al Bimetallic Bars

The paper presents the results of experimental tests of the rolling process of Mg/Al bimetallic bars in two systems of classic passes (horizontal oval-circle-horizontal oval-circle variant I) and modified (multi-radial horizontal oval-multi-radial vertical oval-multi-radial horizontal oval-circle-variant II). The feedstock in the form of round bimetallic bars with a diameter of 22 mm and 30% of the outer aluminum layer was made through explosive welding. The bimetallic bars consisted of an AZ31 magnesium core and a 1050A aluminum outer layer. Bars with a diameter of 17 mm were obtained as a result of rolling in four passes. The rolling process in the passes was conducted at two temperatures of 300 and 400 °C. Based on the analysis of the test results, it was found that the use of modified passes and a lower rolling temperature (300 °C) ensures a more homogenous distribution of the plating layer around the circumference of the core and results in an even grain decreasing, which improves the corrosion resistance of bimetallic bars compared to rolling bars in a classic system of passes and at a higher temperature (400 °C).

Understanding the Enhanced Protective Mechanism of CoCrNiAlY－YSZ－LaMgAl11O19 Double-Ceramic Coating With Aluminum Plating

To understand the enhanced protection mechanism of CoCrNiAlY-YSZ-LaMgAl11O19 dou-ble-layer ceramic coating with aluminum plating, a finite element simulation method was used to simulate the distribution of thermal stress in the coating in all directions. The results show that in the air exposure of the un-aluminized coating, high temperature causes a large radial thermal stress on the surface of the LaMgAl11O19 (LMA) layer, and it increases with the increase in temperature, which is the main reason for the initiation of axial cracks. After arc aluminum plating, the aluminum plating layer effectively inhibited the volume shrinkage of the coating through good adhesion to the coating and internal diffusion, the thermal stress of the coating was considerably reduced, and the CoCrNiAlY-YSZ-LMA coating had an effective enhancement and protection effect; however, there was still a certain amount of shear thermal stress inside the LMA layer, the top of the crack, and the bottom of the crack. This thermal stress caused the initi-ation of radial microcracks in the LMA layer, which also becomes a risk point for the failure of the aluminum coating.

Effect of the Electroless Nickel, Electroless Palladium, and Immersion Gold Multilayer as a Diffusion Barrier on the Bonding Strength of BiTe-Based Thermoelectric Modules

An effective diffusion barrier layer was coated onto the surface of BiTe-based materials to avoid the formation of brittle intermetallic compounds (IMCs) by the diffusion of the constituents of Sn-based solder alloys into the BiTe-based alloys. In this study, the electrochemical deposition of multi-layers, i.e., electroless nickel/electroless palladium/immersion gold (ENEPIG) was explored to enhance the bonding strength of BiTe materials with Cu electrodes. The thermoelectric modules with the ENEPIG plating layer exhibited high bonding strengths of 8.96 MPa and 7.28 MPa for the n- and p-type, respectively that increased slightly to 9.26 MPa and 7.76 MPa, respectively after the thermoelectric modules were heated at 200 °C for 200 h. These bonding strengths were significantly higher than that of the thermoelectric modules without a plating layer.

Identification of the Wear Process of a Silver-Plating Layer by Dual Acoustic Emission Sensing

A method based on acoustic emission (AE) sensing in which two AE sensors are used to measure the tribological characteristics of two interacting friction materials simultaneously in real time was assessed for the in situ measurement and evaluation of the wear process of silver plating. AE sensors were attached to a silver-plated pin and a silver-plated plate, and the two AE signals were measured simultaneously on a pin-on-plate-type reciprocating sliding tester. The resulting changes in the AE signal could be classified into three phases. Surface observations and energy-dispersive X-ray spectroscopy analyses showed that the wear of the silver-plating layer progressed in Phase I, the nickel intermediate layer was exposed and wear of the nickel progressed in Phase II, and the contact electrical resistance increased and the copper substrate was exposed in Phase III. In summary, the wear process of a silver-plating layer, which cannot be identified from the changes in the frictional resistance or the contact electric resistance, can be detected from changes in the dual AE signals. Furthermore, changes in the wear state of both the pin and plate specimens can be identified from differences in the amplitudes of the AE signals and the timing of their detection.

Phase growth in alpha brass with thin layer of electroplated zinc during homogenization annealing

Diffusion mechanism in between thin electroplated Zn coating and Cu – 37wt%Zn substrate during homogenization annealing substantially depends on electroplating parameters. Experiments carried out to determine phase growth and solute profile at various current densities reveal that the increase of current density tends to reduce phase growth. The coefficient of phase growth has been determined and is found to be dependent on the relative density of plating layer.

Plating thickness evaluation with the radial basis functions

The purpose of this work is to evaluate the thickness of the plating layer of vibrating samples using Eddy Current Testing (ECT). In almost previous research, the thickness is evaluated with the fixed liftoff, because the liftoff has an impact on detection signals of the ECT. In this paper, the plating thickness is evaluated in an environment in which the liftoff is greatly changed. A plating thickness evaluation with the Radial Basis Functions was proposed. The thickness of the test sample was evaluated while applying a vibration. It was confirmed that the evaluation result of the method, which uses detection signals in a wide range of liftoffs as calibration signals, was less affected by the liftoff change than the evaluation result of a method which uses phase of detection signals.

Effect of Plating Thickness on Fatigue Strength of Galvanized Steel

Effect of the plating thicknesses on tensile and fatigue properties of hot-dip galvanized steel at room temperature was evaluated. The galvanized steel with thickness of 100 μm and 200 μm were prepared. Both microstructures of η-phase and δ1-phase were similar with each other. In the comparison with the galvanized steel with thickness of 100 μm, the microstructure of ζ-phase for the galvanized steel with thickness of 200 μm was blunt columnar structure due to long immersion time. Tensile and fatigue strengths for a galvanized steel are sensitive to the microstructure of the galvanized layer. The tensile strength and the strength of fatigue limit for the galvanized steel with thickness of 200 μm were smaller than that of 100 μm. In the galvanized steel with thickness of 200 μm, the peeling at plating layer easily occurred. The exfoliated sites have the potential to become subcracks. As the result, the main crack may propagate at early cycles.