High pressure cold spray (hpcs) process as coating treatment for magnesium chassis: an overview

Magnesium, Mg and its alloys have excellent physical and mechanical properties for a number of applications. Mg approximately 35% lighter than aluminum and has exceptional stiffness and damping capacity. Disadvantage of this metal and its alloys are highly susceptible to corrosion, particularly in salt-spray conditions and very susceptible to surface damage due to impact. This paper is an outcome of project to address corrosion problem at Mg chasis part in walkie talkie radio using cold spray technique. Current practise of corrosion treatment for Mg chassis structure is using organic coating contains no heavy metals, fluorides with no effect on the alloy composition upon recycling. Disadvantage of this technique is galvanic corrosion at Mg chassis part after 48hrs of salt spray testing and dull finishing. There is keen interest to explore potential applications of high pressure cold spray (HPCS) process onto Mg structure for corrosion treatment. One of the characteristic of cold spray process is creates a negligible heat-affected zone in the as-deposited material and substrate, therefore generating layers that exhibit excellent fatigue characteristics and spray efficiency in HPCS reaching up to 90%. Due to this features, cold spray is potential solution for corrosion treatment to be applied on Mg chassis structur

INFLUENCE OF CALCIUM HYDROXIDE CONCENTRATION ON THE SYNTHESIS NANOSIZED PRECIPITATED CALCIUM CARBONATE

The precipitated of calcium carbonate has attracted much attention because of its numerous applications in various areas of plastics, textiles, rubbers, adhesives, paints and waste water treatment. Nanosized of precipitated calcium carbonate, (PCC) will enhance the properties and give better performance. Its high purity and close controlled particle size and shape are making it the white filler of choice. Nanosized precipitated calcium carbonate particles were prepared using spraying method. The particles were prepared using three (3) different concentrations of Calcium Hydroxide, Ca(OH)2, three (3) CO2 flow rate and three (3) different calcinations temperatures. The three (3) concentration of Calcium Hydroxide that been used are 25g / 200ml, 25g / 400ml and 25g / 800ml and each of these initial solution sprayed at three (3) different CO2 flow rate, 5l / per-minute, 7l / per-minute and 10l / per-minute. Calcium Carbonate, CaCO3 powders were then calcined at three (3) different temperature, 1100°C, 1200°C and 1300°C. Images from FESEM showed morphology of the particles changed to spindle-like or prismatic when the ionic strength of the Calcium Hydroxide, Ca(OH)2 was increased

Effect of Process Temperature and Time on the Properties of Microwave Plasma Nitrided Ti6Al4V alloy

Titanium alloy (e.g. Ti-6Al-4V) has an excellent combination of properties. However in many cases, the application is limited because of the poor wear property. In this work, a surface modification (plasma nitriding) is carried out to improve the surface properties of Ti-6Al-4V, as a treatment prior to a hardcoating deposition, leading to a duplex coating system. This is an effort to improve the surface and near surface property of Ti-6Al-4V. Plasma nitriding is performed utilizing microwave plasma method in 25% Ar- 75% N2 atmosphere at temperatures of 600°C and 700°C for different processing times (1, 3 and 5 hours). The phase and microstructure of plasma nitrided substrate were characterized by using X-ray diffraction (XRD) and Scanning electron microscopy (SEM). The plasma nitrided Ti-6Al-4V properties (surface roughness, surface hardness and case depth) were determined using profilometer and microhardness, respectively. Results obtained showed a significant increase on the surface hardness of Ti-6Al-4V. This is due to the formation of TiN and Ti2N phases in the form of compound layer. Besides, it shows that the diffusion of nitrogen into the Ti-6Al-4V substrate produces case depth up to 130 μm and this contributes to the improvement of the near surface hardness due to the changes in the microstructures. It was also found that the surface hardness and surface roughness increased with the increases in the process temperature and times

The Influence of Heat Treatment on the Microstructure and Hardness Properties of Ti6Al4V and MgAZ91D Alloys / Yusliza Yusuf...[et al.]

Ti6Al4V alloy and MgAZ91D alloy have excellent combinatorial properties. However, in many cases their applications are limited because of weaknesses in their mechanical properties such as low fatigue strength for MgAZ91D and low modulus elasticity for Ti6Al4V. In this work, the proposed solution is to improve their hardness properties by applying the suitable heat treatment process on these alloys. The heat treatment temperature of Ti6Al4V was performed at 950oC and 900oC, while for MgA91D at 500oC and 450oC. This is followed by water and air quenching and aging treatment at 400oC/4 hours for Ti6Al4V and 200oC/8 hours for MgAZ91D. The results show that the heat treatment process with water quenching medium helps to improve the properties of Ti6Al4V and MgAZ91D alloy in terms of microstructure's changes and generally the value of hardness and roughness was increased after the heat treatment process

Plasma-sprayed TiO2 coatings: Hydrophobicity enhanced by ZnO additions

Titanium dioxide (TiO2) powder mixed individually with 10 and 30 weight percentage (wt%) ZnO was thermally sprayed onto a grade B API 5 L carbon steel substrate by atmospheric plasma spraying. The effect of the addition of ZnO (10 wt% and 30 wt%) on the microstructures and wettability properties of the TiO2/ZnO coatings was investigated. The characterization of the coatings was carried out using scanning electron microscopy, X-ray diffraction (XRD), laser confocal microscope, and sessile droplet system. The XRD analysis of the coat�ing revealed that the anatase phase of TiO2 in the powder state transformed into rutile phases for the produced TiO2/ZnO coatings. Surface microstruc�ture analysis revealed that the coatings had typical micro-roughened surfaces of plasma spraying products. The coating with 30 wt% ZnO produced a coating with remarkable pores and microcracks compared with the TiO2 coating and coating with 10 wt% ZnO. Additionally, the increase in the wt% of ZnO increased the surface roughness value of the produced coatings and substantially changed the wettability properties of the TiO2 coating from hydrophilic to hydrophobic

Effect of Nitriding Temperature and Nitriding Time on MgAZ91D Alloy / Wan Amirul Shafiz Wan Zulkifli...[et al.]

Magnesium and its alloys are widely applied in the automotive industries, electronic and telecommunication industries due to its low densities and excellent strength to the weight ratio. However, it possesses a low surface hardness which can weaken the adhesion properties, especially when hard coating is applied. The need of hard coating is crucial to enhance its corrosion resistance. In this work, nitriding process was carried out to modify the surface properties of MgAZ91D in enhancing its corrosion resistance. The nitriding process was conducted using a high-temperature furnace with the nitrogen gas flow at a constant rate of 5scfh. Three nitriding temperatures were set which were at 300°C, 400°C, and 500°C, for a nitriding period of 1 and 2 hours respectively. Analysis on the surface roughness of the nitrided MgAZ91D was then conducted using MitutoyoSJ410 profilometer. Surface hardness and case depth of the nitride MgAZ91D was analyzed using MitutoyoVicker’s microhardness testing machine. The results showed that the surface hardness, surface roughness, grain size and the case depth of the nitrided MgAZ91D increased through the increase as the process temperature and time. However, the effect of grain size on the case depth hardness is not significant. Thus, the process temperature and time of nitriding MgAZ91D is crucial to be investigated to obtain the right combinations between the surface hardness, surface roughness and case depth for corrosion applications

A preliminary study into the effect of oxide chemistry on the bonding mechanism of cold-sprayed titanium dioxide coatings on SUS316 stainless steel substrate

Current attention has focused on the preparation of thick ceramic coating of nano­structured materials as feedstock material using the thermal spray process. The cold spray method has appeared as a promising process to form ceramic nanostructured coating without significantly changing the microstructure of the initial feedstock materials due to its low processing temperature. However, deposition of ceramic powders by cold spray is not easy due to the brittle characteristics of the material. In this study, TiO2 coatings were deposited on unannealed stainless steel substrates and substrates that were annealed from room temperature to 700 °C prior to spraying. The adhesion strength was evaluated to investigate the bonding mechanism. The influence of the remaining surface oxide layer of chromium oxide, Cr2O3, which is thermodynamically preferred for stainless steel, on the bonding mechanism involved was investigated. The results showed that by increasing the annealing substrate temperature of stainless steel, the adhesion strength of the coatings (thicker oxide) is also increased. As a result, the bonding between the cold-sprayed TiO2 particle and the steel substrate is given by the chemical bonding of an inter-oxide reaction

Antibacterial Properties Of Laser Surface-Textured TiO2/ZnO Ceramic Coatings

Bacterial attachment on surfaces cause fouling, which reduces the hygiene status and effectiveness of equipment. Preventing bacterial attachment on surfaces through surface modification is a potential solution to fouling and has thus become a key research area. In this study, the effect of different ZnO contents (wt%) and picosecond laser surface texturing on the antibacterial properties of TiO2/ZnO ceramic coatings were investigated. The attachment and viability of Escherichia coli (E. coli) bacteria on laser surface-textured and non-textured TiO2/ZnO ceramic coatings were explored. Bacterial growth in an immersion suspension was evaluated using the optical density method. The number of colony-forming units on laser surface textured TiO2/ZnO coatings was found to be lower than that on non-textured coatings, which indicates that laser surface-textured coatings demonstrate strong antibacterial properties. Furthermore, the number of viable E. coli bacteria on laser surfacetextured TiO2/ZnO coatings was observed to be lower than that on non-textured coatings. This finding also demonstrates that laser surface texturing enhances the antibacterial properties of TiO2/ZnO coatings. Overall, laser surface texturing increased the surface areas of the coatings and improved the effectiveness of ZnO as an antibacterial agent. These results prove that laser surface texturing is a successful method for fabricating antibacterial surface

Effect of CO2 Flow Rate on the Synthesis Nanosized Precipitated Calcium Carbonate, PCC

Abstract. The precipitated of calcium carbonate has attractedmuch attention because of its numerous applications in various areas of plastics, textiles, rubbers, adhesives, paints and wastewater treatment. Nanosized of precipitated calcium carbonate,(PCC) will enhance the properties and give better performance. Its high purity and close controlled particle size and shape are making it the white filler of choice. Nanosized precipitated calcium carbonate particles were prepared using spraying method. The particles were prepared using three (3) different concentrations of Calcium Hydroxide,Ca(OH)2, three (3) CO2 flow rate and three (3) different calcinations temperature. The three (3) concentration of Calcium Hydroxide that been used are 25g/200ml, 25g/ 400ml and 25g/800ml and each of these initial solution sprayed at three (3) different CO2 flow rate, 5l/per-minute, 7l/per-minute and 10l/per-minute. Calcium Carbonate,CaCO3 powders were then calcined at three (3) different temperature, 1100°C,1200°C and 1300°C. Images from SEM showed morphology of the particles changed to spindle-like or prismatic when the ionic strength of the Calcium Hydroxide,Ca(OH)2 was increased