Effect of Electric Pulse Treatment on Hot-Dip Aluminizing Coating of Ductile Iron

In this paper, hot-dip aluminizing of ferrite nodular cast iron was carried out after treating liquid aluminum with different electrical pulse parameters. Compared with that of conventional hot-dip aluminizing, the coating structure of the treated sample did not change, the surface was smooth and continuous, and the solidification structure was more uniform. When high voltage and large capacitance were used to treat the liquid aluminum, the thickness and compactness of the coating surface layer increased. The thickness of the alloy layer decreased, and, the compactness and the micro hardness increased, so the electric pulse had a certain inhibition on the formation of the alloy layer. The growth kinetics of the alloy layer showed that the rate-time index decreased from 0.60 for the conventional sample to 0.38 for the electric pulse treated sample. The growth of the alloy layer was controlled by diffusion and interface reaction, but only by diffusion. The AC impedance and polarization curves of the coating showed that the corrosion resistance of hot-dip coating on nodular cast iron was improved by electric pulse treatment.

Determination of Braking Speed of Developed Hybrid Particle Reinforced Aluminium Alloy

Abstract- This paper is aimed at comparing the braking speed of the developed Composite Brake Disc (CBD) with that of a nodular cast iron Honda Accord (2000) Model Brake Disc (HABD). The test samples were produced from Aluminium alloy (Al6061), Coconut Shell Ash (CSA) and Silicon Carbide (SiC) by Stir casting and machined into standard specimens for microstructure analysis, density test, mechanical tests (hardness, tensile and impact), wear test and thermal test. The characterization of coconut shell ash particle was carried out using X-ray Flourescent equipment. Six samples were produced, four composite samples; C1 (70% Al, 5% SiC, 20% CSA), C2 (70% Al, 10% SiC, 15% CSA), C3 (70% Al, 15% SiC, 10% CSA) and C4 (70% Al, 20% SiC, 5% CSA), aluminium alloy sample (A1) and as-cast nodular cast iron sample (N1) obtained from HABD. Sample ‘C4’ had the best physical, mechanical, wear and thermal properties (Densty: 3.15 g/cm3, Hardness: 68 kg/mm2, Tensile Strength: 196.12 N/mm2, Impact Energy: 8.05 J, Wear rate: 0.0002328 g/m, Thermal Conductivity: 72.57 W/m-K) and was used to produce the CBD. From the values of coefficient of frictions obtained for CBD and HABD, the braking speeds were calculated and HABD was seen to have a lower braking speed (56.65 m/s) than the CBD (94.42 m/s) because of its higher coefficient of friction. The higher braking speed of the composite brake disc (CBD) as compared to the Honda Accord Brake Disc (HABD) could be as a result of inadequate reinforcements in the aluminium alloy matrix. Hence, the produced CBD cannot be used as an alternative for the nodular cast iron Honda accord brake disc (HABD) even as problems of heavy weight and breakage that may occur due to heavy impact associated with cast iron brake disc have been addressed using the developed composite.Keywords,- Aluminium Alloy, Braking Speed, Coconut Shell, Composite, Silicon Carbide

Microstructure and Tribological Properties of Fe-Based Laser Cladding Layer on Nodular Cast Iron for Surface Remanufacturing

In this study, a cladding layer and nitriding layer were prepared on nodular cast iron, to provide guidance for remanufacturing of nodular cast iron. Their microstructure and composition and the tribological properties under dry and starved lubrication conditions were studied. Meanwhile, the contact stresses at different friction stages were simulated through the finite element method. The micro-hardness of the cladding layer and nitriding layer were 694 HV0.5 and 724.5 HV0.5, which were 4 times and 4.2 times higher than that of the substrate. For dry friction conditions, the wear resistance of the cladding layer and nitriding layer were 113.2 times and 65.5 times that of the substrate. For starved lubrication conditions, the friction coefficients of the cladding layer and nitriding layer were lower than that of the substrate. In addition, their average friction coefficients and wear resistance were gradually reduced with the increase in load. Contact simulation showed that the maximum equivalent stress gradually increased with the friction coefficient during the dry friction, and the peak value of von Mises stress on the nitriding layer was larger than that of the cladding layer, and the nitriding layer was more likely to yield and peel off.

Ultrasonic Scattering Attenuation in Nodular Cast Iron: Experimental and Simulation Studies

This work evaluates the ultrasonic scattering attenuation of structures with complex scatterer distributions via experimental and simulation studies. The proposed approach uses experimental attenuation knowledge to infer the scatterer size and its concentration in the studied structures, which are important for the effective construction of simulated models. The MATLAB k-Wave toolbox has been used to implement the simulator. Several cast-iron samples have been used to demonstrate the importance of simulation in the characterization of such structures. First, the scattering attenuation was evaluated using the Truell and Papadakis models, and then the results were compared with experimental ones. Emphasis was given to the Papadakis approach because it takes into account the scatterer size distribution. It is demonstrated that both analytical models provide results that are far from the experimental ones. The developed simulator for the studied samples led to a predictive model, in which the attenuation was proportional to the fifth power of the scatterer size, and the corresponding formulation is close to the one proposed by the analytical models.