Study of Dry Sliding Wear and Immersion Corrosion on Al 5083 Reinforced With MWCNT, MoB, and Ni

1. Introduction

Aluminium with its light weight and high strength to weight ratio has extensive use in various industries including marine and aerospace applications. But the low strength and inferior tribological properties of aluminium can lead to premature failure, Panagopoulos and Georgiou (2010). Hence to extend the service life of AMCs in harsh environments, different reinforcements are used to impart required properties to the aluminium matrix to make it suitable for specified applications. The corrosion resistance and wear resistance of Al 5083 need to be enhanced, so that it can be used in marine applications.

CNTs are promising reinforcement with light weight, high aspect ratio, high mechanical strength and self-lubricating property. When CNT wt % goes beyond 1.5 – 2, the mechanical properties are found to be decrement owing to agglomeration. Another concern with CNT is the formation of Al₄C₃ with Al matrix, Carvalho et. al (2014). Yadav et. al (2018) studied the effect of MWCNT on wear characteristics and reported that the synergic effect of SiC and MWCNT improves the wear resistance of the Al-SiC-CNT composite. Mina et. al (2013) reported that CNTs are forming a carbon film over the surface to act as solid lubricant. Mahdi et. al (2018) observed a change in wear mechanism with increase in CNT content on Al 60601. Bustamante et. al (2012) reported on the self-lubricating property of Al-CNT composite with dry wear. Chen et al. (2015) performed corrosion test on Ni - CNT coating and reported that CNT acts as physical obstacle to the corrosion process by packing in micron holes, crevices and gaps on the nickel coating. Mostafa et al. (2012) studied on corrosion behavior of Ni-P-CNT composites and reported that the improvement in corrosion resistance may be due to the generation of a dense layer of the CNT at coating/ electrolyte interface which acts as a physical obstacle.

Mo is a transition metal and with its layered structural oxides improves the lubricating property of the material. The thin oxide layer acts as solid lubricant and reduces the coefficient of friction (Laribi et al., 2016; Dilawary et al., 2018). Heng Tao et al. (2018) studied on CrAlSiN by doping Mo and observed that the lubricating capacity and the anti-wear property at high temperature of 600°C is improved significantly. Dilawary et. al (2018) analysed on Mo alloying of NiCrBSi hard facing up to 700°C and reported enhanced wear resistance due to formation of Mo oxide. Rajamure et al. (2014) investigated on layer surface alloying of Mo and observed that the hard intermetallic formed with layer parameters increased the wear resistance by 5 to 6 times. Hayes et al. (2006) studied the effect of molybdenum in nickel alloy passivation and reported that the molybdenum content strongly influences the repassivation potential. The repassivation behaviour may be because of the formation of molybdenum oxide. It prevents further disintegration of the pit or lowers the acidity of the pit by absorbing H+ ions.

Nickel has a high strength value of 317 MPa and elastic modulus value of 2017 GPa. This makes Ni an important reinforcement for aluminium. The Al–Ni intermetallic are all brittle. Some authors added Al–Ni intermetallics directly as raw materials and some used Ni as reinforcements which caused Al – Ni intermetallics to form which increased the hardness of the composite. Golmohammedi et al. (2015) incorporated Ni particles to A413 alloy and observed that formation of Al₃Ni intermetallics and its uniform distribution significantly influenced the wear mechanism of the composites. Amato et. al (2014) investigated on A356 aluminium alloy laser surface with Ni–Ti–C and observed tremendous decrease in wear rate owing to the formation of Al–Ni and Al–Si–T intermetallic. Reduction in plastic deformation, delamination and adhesive wear are the reasons explained for improved wear resistance. Chen and Alpas (1996) reinforced nickel coated carbon fibres on A356 and reported significant wear resistance owing to improved load bearing capacity of carbon fibres and Al₃Ni intermetallic. Mohammed et al. (2016) reported lower corrosion rates with Ni addition for Al-Cu-Si alloy. They noted a drop-in corrosion resistance for the age hardened alloy at 2.9% Ni as excess Ni initiated more corrosion paths in grain interiors and boundaries. Siyun et al. (2019) reported generation of the corrosion-resistant passive film with SiCp/Al composites coated with Ni.