Yusliza Yusuf

Corrosion behavior of AZ91 Mg-Alloy coated with AlN and TiN in NaCl and Hank’s solution

Magnesium alloys create increasing interest in structural application where weight reduction is vast concern. However, its low corrosion resistance especially in atmosphere environment restricts their wide application. In this study, AlN and TiN were coated on AZ91 Mg alloy using PVD magnetron sputtering. AlN and TiN existence is confirmed via grazing angle x-ray diffraction (GA-XRD). The corrosion behaviors of uncoated and coated AZ91 Mg alloy in3.5% NaCl and Hanks solutions were investigated using a potentiostat during electrochemical corrosion test. AlN and TiN coated samples showed better performance in Hanks solution with TiN coated samples have the least corrosion rate (penetration rate=0.040mm/yr and mass loss rate=0.191g/m2d) in Hanks solution. These create interest to further works on exploring the potential of coated AZ91 Mg alloy in biomaterial application.

Characterization of TiAlBN Nanocomposite Coating Deposited via Radio Frequency Magnetron Sputtering Using Single Hot-Pressed Target

TiAlBN coatings have been deposited at varying bias voltage of 0, -60, and-150 V by radio frequency (RF) magnetron sputtering technique. A single hot-pressed Ti-Al-BN target was used for the deposition process. With glancing angle X-ray diffraction analysis (GAXRD), the nanocrystalline (nc-) (Ti,Al)N phase was identified. In addition, the existence of BN and TiB2 amorphous (a-) phase were detected by X-ray photoelectron spectroscopy (XPS) analysis. Thus, the deposited TiAlBN coatings were confirmed as nc-(Ti,Al)N/a-BN/a-TiB2 nanocomposite. On the other hand, it was found that optimum bias voltage used in present study is-60 V where the deposited TiAlBN coating exhibits an excellent adhesion quality. The adhesion quality of the coatings deposited at-60V bias voltage is classified as HF 1 evaluated using the Rockwell-C adhesion test method (developed by the Union of German Engineers).

The Influence of the Microwave Plasma Nitrided Ti6Al4V Substrate Properties to the Duplex Coating Performance

Titanium alloys, especially TI6Al4V has been used in many industries such as aerospace applications, medical application and automotive applications. This is because it has beneficial properties such as low density, high strength to weight ratio, low modulus elasticity, excellent corrosion resistance and etc. However, titanium and its alloys have limited use in mechanical engineering applications involving sliding wear or abrasion due to poor wear resistance. Therefore, the duplex coating concept was introduced with the intention of the surface modification process as a pre-treatment of the substrate prior to the deposition of hardcoating process. In this study, plasma nitriding of the Ti6Al4V was performed using a microwave plasma technique at 600°C and 700°C for 1 hour, 3 hours and 5 hours, then followed by deposition of chromium nitrate (CrN) on plasma nitrided samples for duplex coating purposes. Microstructural analysis and mirohardness measurement revealed that formation of Ti2N and TiN phase indicating the formation of the compound layer was observed for substrate nitrided at temperature as low as 600°C for 1 hour and a substantial increase on the case depth obtained on plasma nitrided Ti6Al4V was observed with an increase of process temperature and time. The duplex coating obtained in this study has superior surface hardness property and improved load carrying capacity of the coating – substrate system compared to CrN coatings deposited on as received Ti6Al4V which was observed in the penetration depth analysis.

Ti6Al4V Surface Hardness Improvement by Duplex Coating

Ti6Al4V alloy are among the most widely used materials in engineering applications. This is because their relatively beneficial properties. However, inadequate wear properties of Ti6Al4V alloy have largely constrained the application for this material. In this study, Plasma nitriding of the Ti6Al4V was performed using microwave plasma technique at 600°C for 1hour, 3 hours and 5 hours then followed with deposition of CrN on plasma nitrided samples for duplex coating purposes. Microstructural analysis and hardness measurement revealed that formation of Ti2N and TiN phases indicating the formation of compound layer is observed for substrate nitrided at temperature as low as 600°C 1 hour and a substantial increase on the surface hardness of plasma nitrided Ti6Al4V is observed with an increase of process time. The duplex coating obtained in this study has significant surface hardness property and superior as compared with CrN coatings deposited on as received Ti6Al4V.

Corrosion Behavior of Various Surface Treatments TI-6Al-4V Alloy- A Review

A Ti-6Al-4V alloy has been widely used as suitable materials for several of application such as aerospace, marine and biomedical application. Although this alloy is excellent in its properties and good corrosion resistance, the applications are limited because of their poor tribological property referring to the wear resistance property due to their low surface hardness. Therefore, it is inevitable to improve the wear properties of Ti-6Al-4V without detrimental the initial corrosion resistance properties even increasing it for better result. Over the years, various methods of surface treatments for Ti-6Al-4V have been studied and most frequently used are laser treatment, plasma nitriding process, PVD coating and also duplex coating. For each of the surface treatment discussed, several type of corrosion behavior have been studied with the conclusion is comparable to each other. In general, throughout these techniques, the wear resistance property of Ti-6Al-4V was improved and simultaneously improving the corrosion resistance property.

A study on the corrosion and mechanical properties of duplex coating Ti6Al4V/TiAlBN

Titanium alloys, especially Ti6Al4V, have an excellent combination of properties. However, in many cases their application is limited because of poor wear and corrosion properties. In this research, a surface modification (duplex coating) has been carried out to improve the surface properties of Ti6Al4V. The duplex coating of the Ti6Al4V alloy was conducted with the aim of improving the corrosion resistance and mechanical properties of the alloy. In this study, plasma nitriding of Ti6Al4V was performed using a microwave plasma technique at a temperature 600°C for 1 and 3 h, followed by deposition of TiAlBN coating on plasma-nitrided samples for duplex coating purposes. Microstructural measurement revealed that the duplex coating process produces a relatively smooth and crack-free modified surface layer which is believed able to inhibit the occurrence of corrosion process. The electrochemical behaviour of duplex coating samples and untreated Ti6Al4V was evaluated using the Tafel Extrapolation method and it was found that the duplex coating significantly increased the corrosion protection property. In addition, the duplex surface obtained in this study has a superior surface hardness property compared to untreated Ti6Al4V, especially for samples with the longer nitriding time.

Effect of Neodymium and Samarium on the Properties of Bismuth Titanate Ceramics

This paper reported the doping effect on BIT by two different rare-earth compounds i.e. Nd and Sm, each at different mole content (0.25, 0.5, 0.75 and 1.0 mol). The so-called single-step combustion synthesis was used to produce the as-combusted powders, whereby the intermediate calcination step was then eliminated. This method was able to sinter the samples at temperature as low as 1000°C for 3 h. The entire ceramics were characterized for phase detection and stability, microstructure and dielectric properties. It was found that the single phase BIT was successfully formed with Nd and Sm doping. However, little content of pyrochlore phase was detected in the sample with Sm doping particularly at high mole content. (0.5 to 1.0 mol). Besides, a remarkable decrease in the grain size with better microstructure was observed particularly at high mole content (1.0). The improvement in microstructure led to the increase in dielectric constant with low dielectric loss.

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 structure.