Surface and Tribological Properties of Oxide Films on Aluminium Alloy through Fly-Ash Reinforcement

Abstract

Hard anodizing has proven to be a helpful surface treatment for aluminium alloy and typically accompanied by the growth of a porous and highly flawed oxide layer. The presence of pores on the oxide surface can be taken as an advantage in improving the surface properties. Fly-ash particles are high in SiO2 and Al2O3 content and can be utilized as inexpensive strengthening particles, which can increase the wear resistance and microhardness of composite material. It was noticed that limited research had been carried out in utilizing fly-ash as reinforcement on composite oxide coating as a wear resistance candidate. Thus, this study focused on reinforcing fly-ash on oxide coating and investigating its tribological performance. The composite oxide coating was grown on AA2017 aluminium alloy through anodizing process. To understand the effect of anodizing time and fly-ash content, the parameters were varied from 5–60 min and 0–50 g/L, respectively. The findings suggested that 60 min of anodizing time provides the highest thickness and surface roughness at 35 µm and 6.5 µm, respectively. Interestingly, composite oxide coating with 50 g/L fly-ash provides the highest coating thickness but has the lowest roughness at 52 μm and 8.2 μm, respectively. The composite oxide coatings are observed to reduce friction only for a limited time, despite their potential in significantly reducing the wear rate. The wear mechanism observed was adhesion, micro-crack, and delamination. The findings of this study are believed to provide insight on the potential of fly-ash to be a reinforcement for wear-reduction materials.

Effect of pulse current on surface properties of aluminum oxide coating containing graphite

“…From the literature, it is well known that 60 min of anodizing time was adequate for producing thick oxide coatings and enough to offer effective protection against wear and corrosion. 21,45 In summary, results show that the pulse anodizing significantly decreased the surface roughness, pores dimensions as well as minimize crater formation on the composite oxide coating. Furthermore, pulse anodizing allows utilization of the "recovery effect" that result in reducing the growth rate of oxide layer and thus, improve the oxide uniformity.…”

“…Figure 4 represents the 3D profiles of the uncoated AA2017‐T4 Al alloy and composite oxide coatings after being anodized by DC and PC for 5 to 60 min. Several color regions ordered from red, orange, yellow, green, and blue are used to denote the crests and troughs on a topographic image 21,45 . The blue region represents the lowest area (trough), while the red region is the highest elevation in the area (crest) 19 .…”

“…In relation to increment of pore dimensions at 60 min anodization, the larger pores leads to an increase in surface roughness (shown in Figure 5). From the literature, it is well known that 60 min of anodizing time was adequate for producing thick oxide coatings and enough to offer effective protection against wear and corrosion 21,45 …”

“…yellow, green, and blue are used to denote the crests and troughs on a topographic image. 21,45 The blue region represents the lowest area (trough), while the red region is the highest elevation in the area (crest). 19 The average surface roughness (R a ) value indicates the average of surface heights (asperities) and depths (valley) across the surface, and it is an important parameter for analyzing surface topographic properties.…”

Analysis of the Surface Stereometry of Alloyed Austenitic Steel after Fibre Laser Cutting using Confocal Microscopy

“…Sometimes different types of techniques are used to improve the adhesion of coatings, such as surface anodising using aluminium, electrochemical or plasma methods, or blasting, sandblasting and sodding. Ra is the most common surface roughness parameter used to measure flat surfaces [44,45]. However, without the determination of volumetric parameters such as Vvv (valley void volume) and Vvc (core void volume), the surface during electrolytic etching may lose the ability to mechanically anchor the coating.…”