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

Effects of Process Temperature and Time on the Properties of Microwave Plasma Nitrided Ti-6Al-4V 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 substrate treatment on load carrying capacity of Ti6Al4V Duplex Coating

In this work, duplex coating is carried out by conducting microwave plasma nitriding on Ti6Al4V, followed by the deposition of hardcoating (CrN) using arc coating system. Plasma nitriding of Ti6Al4V alloy using microwave plasma technique, created a thick (~130µm) modified layer (case depth) at processing temperature of 700°C and 5 hour. The load carrying capacity of the duplex coating assessed using Rockwell-C test shows that case depth increase with an increased in process temperature and time for nitriding. Consequently, affect the formation of compound layer on the plasma nitrided specimen. Moreover, the formation of compound layer may lead to uneven distributions of the hardcoating (CrN) applied resulted in poor adhesion of hard coating - nitrided substrate

Chemical Composition Analysis of TiAlBN Nanocomposite Coating Deposited via RF Magnetron Sputtering

TiAlBN nanocomposite coating have been successfully deposited on AISI 316 substrate via RF magnetron sputtering by varying nitrogen-to-total flow ratio (RN) of 5, 15, 20, 25%, as well as varying substrate temperature of 100, 200, 300, and 400 ºC; using single Ti-Al-BN hot-pressed target. Chemical compositions of the coatings were analysed using X-ray photoelectron spectroscopy (XPS). XPS results showed that the TiAlBN nanocomposite coating reaches a nitride saturated state at higher RN (e.g 15, 20, and 25%) and boron concentration was found to be approximately 9 at.%. However, as the concentration of nitrogen decreases at lower RN (5%), boron concentration was found to increase to 16.17 at. %. This is due to the increase of TiB2 phase in the coating. Variations of substrate temperatures were found to give no significant effect on the chemical composition of the deposited TiAlBN nanocomposite coating

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 600oC 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 600oC 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

Effect of Grain Size on the Corrosion Behavior of TiAlBN Nanocomposite Coating

TiAlBN nanocomposite coating have been deposited by varying nitrogen-to-total gas flow rate ratio (RN) of 5, 15, 20, 25%, and varying substrate temperature of 100, 200, 300, and 400 °C. The coating was deposited on AISI 316 substrates using radio frequency (RF) magnetron sputtering with single Ti-Al-BN hot-pressed target. The crystallographic phase, structural, and grain size was evaluated using glancing angle X-ray diffraction analysis (GAXRD). The corrosion behavior of the coating was determined using potentiodynamic polarization test. The grains size of the deposited coating (calculated using Scherrer’s formula) were found to be in the range of 3.5 to 5.7 nm. It was also found that the grain size affects the corrosion behavior of the coating in which larger grain size decreases the corrosion resistance of the deposited TiAlBN nanocomposite coating. In addition, it was observed that the corrosion resistance of the coating is lower than the substrate material. Nevertheless, the coating was able to protect the surface of the uncoated AISI 316 substrate from pitting corrosion. Moreover, the coating exhibited a corrosion resistance comparable with other high corrosion resistance coatings such as (Ti,Al)N, and TiAlSiN

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 600oC 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 600oC 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

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 theother 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)

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 Hank’s solutions were investigated using a potentiostat during electrochemical corrosion test. AlN and TiN coated samples showed better performance in Hank’s solution with TiN coated samples have the least corrosion rate (penetration rate=0.040mm/yr and mass loss rate=0.191g/m2d) in Hank’s solution. These create interest to further works on exploring the potential of coated AZ91 Mg alloy in biomaterial application