Patricia Popoola

NiTi Intermetallic Surface Coatings by Laser Metal Deposition for Improving Wear Properties of Ti-6Al-4V Substrates

The NiTi intermetallic possesses a number of good properties, such as high wear, oxidation, and corrosion resistance. This paper focuses on the deposition of NiTi intermetallic coatings on Ti6Al4V substrate by laser melting of Ti and Ni elemental powder mixtures. The effect of varying the Ti content in the NiTi composition on the microstructure and wear properties of the coatings was investigated. The microstructure of the NiTi intermetallic coatings were characterized by the scanning electron microscope (SEM) equipped with Energy Dispersive Spectroscope (EDS). The wear properties of the coatings were performed under accelerated dry sliding wear tests. The results obtained from the SEM/EDS analysis; show that the coatings consist of Ni and Ti elements from the feedstock, and the NiTi, NiTi2 and NiTi3, intermetallic phases. Dry sliding wear analysis revealed that there is correlation between the hardness and the wear rate. The coatings displayed significant improvement in wear resistance up to 80% compared to the substrate.

Inhibitive Action of Ferrous Gluconate on Aluminum Alloy in Saline Environment

The corrosion of aluminum in saline environment in the presence of ferrous gluconate was studied using weight loss and linear polarization methods. The corrosion rates were studied in different concentrations of ferrous gluconate 0.5, 1.0, 1.5, and 2.0 g/mL at 28°C. Experimental results revealed that ferrous gluconate in saline environment reduced the corrosion rate of aluminum alloy at the different concentrations studied. The minimum inhibition efficiency was obtained at 1.5 g/mL concentration of inhibitor while the optimum inhibition efficiency was achieved with 1.0 g/mL inhibitor concentration. The results showed that adsorption of ferrous gluconate on the aluminium alloy surface fits Langmuir adsorption isotherm. The potentiodynamic polarization results showed that ferrous gluconate is a mixed type inhibitor. Ferrous gluconate acted as an effective inhibitor for aluminium alloy within the temperature and concentration range studied. The data obtained from weight loss and potentiodynamic polarization methods were in good agreement.

Computational Dynamics of Anti-Corrosion Performance of Laser Alloyed Metallic Materials

Laser surface alloying (LSA) is a material processing technique that utilizes the high pow‐ er density available from defocused laser beam to melt both reinforcement powders and a part of the underlying substrate. Because melting occurs solitary at the surface, large temperature gradients exist across the boundary between the underlying solid substrate and the melted surface region, which results in rapid self-quenching and resolidifications. Reinforcement powders are deposited in the molten pool of the substrate to produce cor‐ rosion-resistant coatings. These processes influence the structure and properties of the al‐ loyed region. A 3D mathematical model is developed to obtain insights on the behavior of laser melted pools subjected to various process parameters. It is expected that the melt pool flow, thermal and solidification characteristics will have a profound effect on the mi‐ crostructure of the solidified region.

Current Methods for the Remediation of Acid Mine Drainage Including Continuous Removal of Metals From Wastewater and Mine Dump

Abstract The remediation of acid mine drainage (AMD) in terms of effluents/dumps treatment can be highly complicated due to several factors to be considered such as, but not limited to, its composition. The majority of economically mine deposits are associated with potentially hazardous trace and harmful elements. AMD is water body rich in acidic metal formed by the reaction between the water and rock containing sulfur-bearing minerals. In the last twodecades, researchers have used various techniques such as chemical precipitation, solvent extraction, ultrafiltration, microfiltration, nanofiltration, reverse osmosis, organic and inorganic ion exchange, and adsorption in mine water/dump treatment. The importance, achievements, and limitations of various techniques with references to their major functions were identified in this section. In this regard, comprehensive investigation was done on the previous and recent/novel methods in reversing the environmental damages caused by AMD. Moreover, technology screening in selecting suitable treatment technique based on the factors such as cost, appropriateness, health and environmental impact, public perception, and acceptance of the techniques was analyzed based on the literature review.

Electrodeposition of Functional Coatings on Bipolar Plates for Fuel Cell Applications – A Review

The issue of corrosion and degradation has been evaluated as one of the major sour‐ ces of concern in the history and trend of materials development and their applica‐ tions in engineering. Design, process, and production consideration of materials hinge on the motive of built-to-last technology in their lifetime applications. The “World Corrosion Organization” has calculated that the direct cost of corrosion worldwide is over 3% of global gross domestic product (GDP)—approximately US

Nd: YAG laser treatment of aluminium —C TiB2 coated: Optimization of corrosion properties

2.2 trillion—every year. Natural materials tend to return to their original stable states after being conformed through processes into engineering applications. In order to conserve materials’ in‐ tegrity, usability, safety, and performance, the materials have to be subjected to processes that will keep them in its optimal functionalities. The finishing phase of most materials for engineering applications is usually done with protective barrier in the form of coating, paint, or furnishes to conserve the materials’ integrity and inhibit its susceptibility to interact with the environment. Complete overhauling of a whole corrosion-invaded device is capital intensive. Corrective maintenance through repair work on damaged parts is not economically viable. To minimize or avoid these costs, adoption of functional composite coatings using electrodeposition can be effective. Bipolar plate of fuel cell is a key performance component with corrosion challenge. This chapter will focus on electrodeposition as one of the corrosion inhibition tech‐ niques on bipolar plate of fuel cell [1, 2]. Through electrodeposition, bipolar plate can be protected with appropriate functional coatings to enhance surface quality and impart good surface properties that will prolong lifespan application in fuel cell vehicles.

The effect of multiple laser alloyed tracklines on the corrosion properties of Al-MMC

As the reports in the literature regarding corrosion performance of Al/TiB2 MMC are rather contradictory, the optimization of laser surface alloying parameters for these composite coatings seems to be necessary. The characterization of the MMC was carried out by optical microscopy (OM), scanning electron microscopy (SEM/EDS) and x-ray diffraction (XRD). Partial melting of the alloying powder occurred and the chemical reactions with the a-Al in the matrix led to the formation of AlTi and AlB2 phases. Eutectics of TiB2/Al and TiB2/Ti were observed. The results of the tests indicate that TiB2 reinforcement does not give significant increase in microhardness of aluminium. The corrosion resistance of a single laser trackline MMC in a 3.65 % NaCl solution was improved, especially for the sample produced at high scan speed, with the lowest volume fraction of TiB2 particles.

Compositional effect of Zr-containing ceramic on phase and microstructural evolution of Ti–SiC laser clad coatings

In real life engineering applications, production of large area coverage is often required especially for preventing material loss and component damage. To enhance such applications, multiple tracklines laser surface alloying of Al/TiB2 was performed to obtain a large area coverage using Nd:YAG laser. The overlap rate was 50%. The characterization of the metal matrix composite was carried out by optical microscopy (OM), scanning electron microscopy (SEM), and x-ray diffraction (XRD). Results indicated that the microstructure consist of high concentration of TiB2 distributed in the solid solution at front zone of the tracks corresponding to the overlapped region while the track centers contain similar microstructure but with lower content of TiB2 as indicated by energy dispersive spectrometry (EDS). This microstructure is basically similar to that of a single alloyed trackline, but with different percentages of TiB2 reinforcement. The measured microhardness of the overlapped sample decreased with about 11....

Development of carbon anode for cathodic protection of mild steel in chloride environment

ABSTRACT The Ti–SiC–ZrB2 cermet coatings were fabricated on Ti6Al4 V by laser cladding with a 4 kW continuous wave Rofin Sinar Nd:YAG laser system. Three compositions of the cermet coatings of varying percentages of ZrB2 (0 wt-%, 5 wt-% and 10 wt-%) were added. Scanning electron microscopy and energy dispersive spectroscopy were used to study the microstructure of the coatings while X-ray diffractometry was utilised to investigate the existing phases on the coatings. The microstructures of the coatings were majorly characterised by secondary precipitates of granular TiC and Ti5Si3 in β-Ti matrix. With the addition of ZrB2, new phases developed which were dispersed. This resulted in a corresponding increase in surface hardness where the resultant hardness values of the laser clad coatings were found to be approximately four times higher than Ti6Al4 V alloy.

MEMBRANE SELECTION FOR ORGANIC CONTAMINANTS REMOVAL FROM HARTBEESPOORT DAM WATER IN SOUTH AFRICA

Purpose The purpose of this paper is to develop technically efficient and economically effective sacrificial anodes that can be used for cathodic protection (CP) of pipelines in marine environment and fill the knowledge gap in the use of carbon anodes for CP. Design/methodology/approach A sacrificial anode was produced via sand casting by adding varying weight-percent of coal and ferrosilicon to a constant weight-percent of grey cast iron. The hardness of the produced anodes was evaluated using a Rockwell hardness tester. The microstructure of the anodes was observed with scanning electron microscope/energy-dispersive spectroscopy (SEM/EDS). X-ray diffraction (XRD) was used to study the phases present. A potentiostat was used to assess the corrosion behaviour of the produced anodes and mild steel in 3.5 Wt.% NaCl solution. Findings The SEM results showed that some anodes had interdendritic graphite formation, while others had pronounced graphite flakes. The EDS analysis showed carbon and iron to be the prominent elements in the anode. Anodes Bc, B2 and B5 with a corrosion rate of two order of magnitudes were observed to have similar dendritic structures. Anode B4 is the most electronegative with an Ecorr of −670.274 mV Ag/AgCl and a corrosion rate of 0.052475 mmpy. The produced anodes can be used to protect mild steel in the same environment owing to their lower Ecorr values compared to that of mild steel −540.907 mV Ag/AgCl. Originality/value Alloying has been majorly used to improve the efficiency of sacrificial anodes and to alleviate its setbacks. However, development of more technically efficient and economically effective sacrificial anodes via production of composite has not been exhaustively considered. Hence, this research focuses on the development of a carbon based anode by adding natural occurring coal and ferrosilicon to grey cast iron. The corrosion behaviour of the produced anode was evaluated and compared to that of mild steel in marine environment.