Alternating Current Electrophoretic Deposition of Hydroxyapatite Composite Coating on Mg-0.8wt.%Ca-3%wt.%Zn alloy

The present work investigates the AC electrophoretic deposition of nano-sized  HAP composite coating on Mg-0.8wt.%Ca-3%wt.%Zn alloy.  Nano HAP powder was prepared using hydrothermal microwave assisted technique. HAP coating is deposited electrophoretically from dispersing medium (ETELAC) forming composite coating on the alloy surface.  Electrophoretic deposition experiments were conducted as single run (S), double run (D) and multirun (M). The properties of HAP coating regarding adhesion, morphology and corrosion behavior were thoroughly investigated.Results show that the best coating regarding the weight gain as well as the morphology was obtained from multi run (M) experiments of  5%HAP and 5% ETELAC at 200 V under 150 rpm stirring.  Electrochemical Impedance (EIS) investigation show that HAP composite coating posses a high corrosion resistance compared to the substrate alloy.  The mechanism of HAP/ETELAC coating formation was thoroughly discussed

Enhancing Corrosion Resistance of Stainless Steel 304 Using Laser Surface Treatment

Stainless steel AISI 304 was laser treated to enhance corrosion resistance and improve surface properties. This alloy has many applications in auto industry (car body) as well as oil and gas industry. Different conditions were applied in the laser surface treatment, namely: laser power density, scan speed, distance between paths, medium gas (air, argon and nitrogen). After laser treatment, the samples microstructures were investigated using optical microscope to examine microstructural changes due to laser irradiation. Specimen surfaces were investigated using XRD, SEM and EDAX before and after laser treatment to examine the surface composition changes brought by laser irradiation. Results showed that laser irradiation enhances the corrosion resistance of AISI 304 Stainless steel to a large extent. Corrosion rates as low as 0.011 mpy for laser treated samples were obtained in comparison to 0.952 mpy obtained for the untreated samples. Superior pitting corrosion resistance was obtained under specific treatment conditions. The enhancement of corrosion resistance depends on the laser irradiation conditions. The corrosion protection afforded by laser treatment is attributed mainly to the grain refinement of the top surface layer. This layer is found to consist of nano-scale grains

Improvement ductility and corrosion resistance of CoCrFeNi and AlCoCrFeNi HEAs by electroless copper technique

In this study, the effect of copper coated particles on the properties of CoCrFeNi and AlCoCrFeNi high entropy alloys (HEAs) was studied. Mechanical milling is applied to achieve a good homogeneous distribution of an equiatomic CoCrFeNi and AlCoCrFeNi HEAs for 25 h milling time, followed by an electroless copper plating with 5–20 wt.% Cu by 5 wt.%, have been established. The prepared powder alloys were compacted at 800 MPa, then sintered at 1150 °C, 1200 °C, 1250 °C for Cux/(CoCrFeNi)1-x HEA and 900 °C, 950 °C, and 1000 °C for Cux/(AlCoCrFeNi)1-x HEA in a vacuum furnace for 90 min. The correlation between the microstructure, density, hardness, wear behavior and corrosion resistance of the fabricated CoCrFeNi, Cux/(CoCrFeNi)1-x and Cux/(AlCoCrFeNi)1-x HEAs were investigated. The results revealed that, alloys which sintered at 1200 °C for (CoCrFeNi – Cux/(CoCrFeNi)1-x HEAs) and at 950 °C for (Cux/(AlCoCrFeNi)1-x HEA) exhibit the highest relative density. Densification was enhanced as a result of increasing the nano Cu wt.% content. A dramatic decrease in the produced samples’ hardness was observed where it decreased from 189.1 HV to 134.5 HV for Cux/(CoCrFeNi)1-x and from 403 HV to 191 HV for Cux/(AlCoCrFeNi)1-x HEAs by the addition of the nano Cu wt.% content. In addition, Wear rate is increased gradually by the addition of the nano Cu wt.% content. The electrochemical results indicate that an increased nano Cu wt.% content corresponds to an increased corrosion rate from 0.297 mm/year to 1.84 mm/year for Cux/(CoCrFeNi)1-x and from 0.03 mm/year to 0.093 mm/year for Cux/(AlCoCrFeNi)1-x HEAs