Multi-objective optimization of alloying elements to enhance the wear resistance and impact strength of HCCI produced by furan sand mold

High Chromium White Cast Iron (HCWCI) plays a major role in manufacturing of wear-resistant components. Due to unique wear resistance property, attribution to the additions of carbide forming elements, they have been used for mill liner applications. By varying the wt% of alloying elements such as Cr, Ti, and Mo, the wear resistance and impact strength of High Chromium Cast Iron (HCCI) can be increased. To enhance the wear resistance property according to Central Composite Design (CCD), 16 samples were fabricated by varying the wt% of alloying elements. To fabricate the samples, furan sand molds were prepared and used for the further casting process. The properties of Furan sand mold enhance the mechanical properties and reduce the mold rejection rate, production time, etc. To attain the optimum Wear Rate (WR) and Impact Strength (IS) value without dominance, optimization techniques such as Response Surface Methodological (RSM) and Particle swarm optimization (PSO) are employed to solve the multi-objective problem. The RSM and PSO predicted optimum solutions are compared by using the Weighted Aggregated Sum Product Assessment (WASPAS) ranking method. The WASPAS result revealed that when compared to the RSM result, the PSO predicted optimal wt% of chemical composition (22 wt % Cr, 3 wt % Ti, and 2.99 wt % Mo) gives the optimum WR value (53 mm3/min) and IS value (3.77 J). To validate the PSO result, experiments were carried out for the predicted wt% of alloying elements and tested. The difference between the PSO predicted result and experimental result is less than 5% error which clearly shows that PSO is an effective method to solve the multi-objective problem.

Study on the Influence of Compression Ratio on the Rail Contact Fatigue Resistance Property and Its Mechanism

Contact fatigue resistance properties of four commercial steel rails were systematically studied and compared. The contact fatigue limit cycles, fracture toughness, and fatigue crack growth rate of the corresponding rails with different compression ratios were tested and analyzed, which showed a close relationship between them. Moreover, microstructures of the rails were carefully observed by using the TEM to elucidate the scientific mechanisms. Observations and obtained results indicated that pearlite lamellar spacing further decreased with the rise of compression ratio, which greatly and rightly contributed to the improved fatigue resistance property.

Effect of Energy Density on the Microstructure and Properties of the CrFeCoNiNb High Entropy Cladded Layer

A synergistic combination of mechanical properties and corrosion resistance property is desired for most ocean engineering structural applications. In this paper, we prepared high entropy alloy (HEA) cladded layer of composition CrFeCoNiNb (atomic%). We aim to attain a balance between the mechanical property and the corrosion resistance property through adjusting the energy density. The prepared CrFeCoNiNb cladded layer with the energy density of 116.7J/mm2 exhibited excellent mechanical properties and high corrosion resistance. The improved mechanical properties are attributed to the fine grain strengthening, solid solution strengthening and dispersion strengthening. Whereas the excellent corrosion resistance is due to the fine grained BCC single phase structure and the compact passivation film. The variation of the mechanical properties and corrosion resistance with different energy densities are attribute to the phase composition. The diffraction peak area of the main phase of BCC decreases first and then increases with the increase of energy density, which is the main reason that the hardness of the cladded layer follows the similar trend. The outcome of our research suggests that the prepared CrFeCoNiNb cladded layer could be explored to realise surface strengthening of load-bearing parts in marine engineering equipment.