Adetayo A. Adebisi

Effect of variable particle size reinforcement on mechanical and wear properties of 6061Al–SiCp composite

Abstract The influence of reinforcement particle size variation plays a major role on the properties of Al–SiCp composite. Therefore, this study aim to investigate the mechanical and wear performance of single particle size (SPS) and multiple particle size (MPS) Al–SiCp composite prepared by stir casting process. The SPS comprises three categories; fine (15 μm), intermediate (40 μm) and coarse (80 μm) particle sizes and combination of the three sizes accounts for the MPS in the ratio 1:1:2, respectively. Oxidation of the SiCp and addition of 1 wt% Mg during composite processing resulted to interface reaction products such as MgO (magnesium oxide) and MgAl2O4 (magnesium aluminate) which suppresses the potential formation of undesired Al3C4 (aluminium carbide). The study reveals that MPS composite improved the hardness and impact properties with enhanced wear performance compared to SPS composite. Characterization of the composite morphology and phases was performed using scanning electron microscope and X-ray diffraction analysis. This study provides an effective method of optimizing the properties of Al–SiCp composite by integrating MPS with low volume fraction of reinforcement phase.

Preparation and characterisation of TIG-alloyed hybrid composite coatings for high-temperature tribological applications

There is an increasing interest in the tribology community for developing high-performance composite coatings to meet severe tribological conditions in advanced mechanical systems which require high operating temperature and long life. In the present work, powder preplacement and tungsten inert gas (TIG) torch melting techniques have been employed to generate titanium carbide (TiC)-based composite coatings containing hexagonal boron nitride (hBN) or Ni–P coated hBN (Ni–P-hBN) lubricant additive. The effects of preplaced powder composition on the cross-sectional microstructures and surface hardnesses of the developed coatings were analysed. Furthermore, the friction and wear behaviours of the composite coatings at 600°C were evaluated using a Ducom ball-on-disc wear test rig. The results indicate that the TIG-melted surface containing TiC and Ni–P-hBN powder mixtures exhibits optimum properties combining good control of microstructures and uniformly distributed hardness as well as excellent tribological properties due to the enhanced wettability action of Ni–P encapsulated hBN particles.

Optimization of tribological performance of SiC embedded composite coating via Taguchi analysis approach

Tungsten inert gas (TIG) torch is one of the most recently used heat source for surface modification of engineering parts, giving similar results to the more expensive high power laser technique. In this study, ceramic-based embedded composite coating has been produced by precoated silicon carbide (SiC) powders on the AISI 4340 low alloy steel substrate using TIG welding torch process. A design of experiment based on Taguchi approach has been adopted to optimize the TIG cladding process parameters. The L9 orthogonal array and the signal-to-noise was used to study the effect of TIG welding parameters such as arc current, travelling speed, welding voltage and argon flow rate on tribological response behaviour (wear rate, surface roughness and wear track width). The objective of the study was to identify optimal design parameter that significantly minimizes each of the surface quality characteristics. The analysis of the experimental results revealed that the argon flow rate was found to be the most influential factor contributing to the minimum wear and surface roughness of the modified coating surface. On the other hand, the key factor in reducing wear scar is the welding voltage. Finally, a convenient and economical Taguchi approach used in this study was efficient to find out optimal factor settings for obtaining minimum wear rate, wear scar and surface roughness responses in TIG-coated surfaces.

Investigation of Parametric Influence on the Properties of Al6061-SiCp Composite

The influence of process parameter in stir casting play a major role on the development of aluminium reinforced silicon carbide particle (Al-SiCp) composite. This study aims to investigate the influence of process parameters on wear and density properties of Al-SiCp composite using stir casting technique. Experimental data are generated based on a four-factors-five-level central composite design of response surface methodology. Analysis of variance is utilized to confirm the adequacy and validity of developed models considering the significant model terms. Optimization of the process parameters adequately predicts the Al-SiCp composite properties with stirring speed as the most influencing factor. The aim of optimization process is to minimize wear and maximum density. The multiple objective optimization (MOO) achieved an optimal value of 14 wt% reinforcement fraction (RF), 460 rpm stirring speed (SS), 820 °C processing temperature (PTemp) and 150 secs processing time (PT). Considering the optimum parametric combination, wear mass loss achieved a minimum of 1 x 10-3g and maximum density value of 2.780g/mm3 with a confidence and desirability level of 95.5%.

Abrasive wear response of TIG-melted TiC composite coating: Taguchi approach

In this study, Taguchi design of experiment approach has been applied to assess wear behaviour of TiC composite coatings deposited on AISI 4340 steel substrates by novel powder preplacement and TIG torch melting processes. To study the abrasive wear behaviour of these coatings against alumina ball at 600o C, a Taguchi’s orthogonal array is used to acquire the wear test data for determining optimal parameters that lead to the minimization of wear rate. Composite coatings are developed based on Taguchi’s L-16 orthogonal array experiment with three process parameters (welding current, welding speed, welding voltage and shielding gas flow rate) at four levels. In this technique, mean response and signal-to-noise ratio are used to evaluate the influence of the TIG process parameters on the wear rate performance of the composite coated surfaces. The results reveal that welding voltage is the most significant control parameter for minimizing wear rate while the current presents the least contribution to the wear rate reduction. The study also shows the best optimal condition has been arrived at A3 (90 A), B4 (2.5 mm/s), C3 (30 V) and D3 (20 L/min), which gives minimum wear rate in TiC embedded coatings. Finally, a confirmatory experiment has been conducted to verify the optimized result and shows that the error between the predicted values and the experimental observation at the optimal condition lies within the limit of 4.7 %. Thus, the validity of the optimum condition for the coatings is established.

Performance assessment of aluminium composite material for automotive brake rotor

Application of composite material for brake rotor has the potential to improve braking performance due to its attractive properties when compared to cast iron material. Aluminium composite has superior specific strength, higher coefficient of thermal expansion/heat dissipation rate with low mass density. These characteristics possess the tendency to influence undesirable conditions during braking. In this study, composite brake rotor was fabricated using stir casting process and performance assessment was conducted with a passenger car brake system setup. The rotor achieved 50% weight reduction and the braking result reveals that composite rotor exhibited uniform thermal trend with 25% heat dissipation rate for braking pressure within the range of 1.5–2.0 MPa over cast iron. The contour trend of cast iron rotor exhibited high temperature zone which gives rise to formation of intermittent hot spot which is detrimental to braking conditions. Simulation modelling analysis showed good agreement with actual operating test measurements. Conclusively, composites are commercially viable and feasible to replace the existing cast iron material.