Papers by Keyword: Hardness

Abstract: The mechanical properties of anodic oxide films of Nb, Ta and Zr were studied by the nanoindentation method. Anomalously high elastic recovery after deformation was observed for oxides with thickness of 20 nm. An analogue of this behavior can be elastic membrane fixed on soft base that does not prevent the membrane from bending. Increase of the oxide thickness to 300 nm reduced the effect associated with the high elasticity of oxide and easy deformation of the soft metal substrate, and was accompanied by an increase in the plastic component of deformation, which is similar to the behavior of ceramic materials with low elastic and significant residual plastic deformation.

Abstract: The present work includes an investigation of the effect of α-alumina nanoparticles addition to aluminum-based nanocomposites on its mechanical properties and finding the optimal value of alumina nanoparticles that give the best properties. Experimental work includes manufacturing samples of aluminum-based nanocomposite reinforced with alumina nanoparticles by powder metallurgy- hot forging process. Mechanical properties were tested. The results show an increase in hardness and compression yield strength with increasing the weight percentage of alumina nanoparticles, while the wear rate decreased to certain percentages of addition and then increased again. From the experimental results, multiple regression analysis methods have been used to obtain an empirical equation for predicting the mechanical properties and describe the behavior of hardness, compression strength, and wear rate. Genetic Algorithm Optimization was applied to find the optimum value of alumina nanoparticles weight percentage which gives good mechanical properties.

Abstract: The efficiency, precision, and expected lifespan of mechanisms and machine components (such as ball bearings, couplings, and gauges) are significantly influenced by the quality of the materials used. Thus, it is essential to select materials that offer well-defined hardness and stability throughout the product's lifetime. This paper examines the heat treatment applied to 100Cr6 steel to achieve precise hardness in the range of 230–390 HV10, while also meeting requirements for stability and uniformity over the product's lifespan.

Abstract: Modern engineering components require composites that are robust, lightweight, and inexpensive as integrated particulate for solid strengthening and corrosion resistance alloy. This study envisions a snail shell particulate (SSP) as a potential biofillers on aluminium alloy due to its inherent characteristics. The fabrication of the developed alloy was done through liquid stir casting method with determination to examine the correspondent physical, optoelectrical, electrochemical, and microstructural behaviour for chemical application. Composite infringement varies from 10% - 25% SSP after optimization using design of experiment. The result of electrochemical analysis showed a notable decrease in corrosion rate with increased SSP content from 12.06 mm/yr, of control sample to (75Al-25SSP) which had a corrosion rate of 7.59 mm/yr, resulting in a 40.1% drop-in degradation rate. Notably, microhardness properties increase from 28.1 to 45.5 HRB as a result of solid strengthening characteristics of doped fillers. Opto-electrical assessment demonstrated decreasing resistivity with higher SSP content, indicating improved current flow resistance. The microstructural properties showcased SSP's distinctive dispersion with few micro pores. The intermetallic phases confirmed their integration into the metal matrix by providing an enhancing adhesion and solid crystalline structure.

Abstract: This study aims to predict the hardness of electrodeposited Ni-W alloy coatings by combining machine learning methods based on a small dataset, with the goal of streamlining the trial-and-error process and reducing experimental costs. In this study, 11 features comprised of electrolyte compositions and process parameters (including current density, pH value, bath temperature, and agitation) were utilized as input parameters, with coating hardness serving as the target value. Two machine learning models (KNN and Elastic-Net) were employed to predict coating hardness, and hyperparameters were tuned using Randomized-Search CV (CV=5). The results demonstrate that the KNN model exhibits the highest predictive accuracy, with R²=0.942 and RMSE=0.0658. The SHAP method was used to analyze the importance of features and their impact on hardness. It is found that bath temperature, current density, and ammonium chloride concentration have the most significant influence on coating hardness. This study demonstrates how machine learning can enhance electrodeposition to predict coating hardness, offering insights for improving Ni-W alloy coatings in mechanical applications.

Abstract: Advanced high-strength steels (AHSS) have their current applications directed mainly to the automotive industry, where they use modern metallurgical techniques to develop microstructures with retained austenite, which leads to an improvement in the combination of strength and ductility through transformation-induced-plasticity (TRIP). The main priority of the research work will be a detailed examination and optimization of the heat treatment parameters of medium-manganese steels, specifically by the Quenching and Partitioning (Q&P) method and the expansion of experimental data related to the increase of wear resistance of these materials. The issue of the application of medium-manganese high-strength AHSS steels in the field of tribology is currently very relevant. Mid-manganese AHSS steels, which show significant wear resistance, have the potential to replace traditional Hadfield Mn steels that contain 10-14 wt. % manganese. With the help of specifically designed heating and cooling cycles, it is possible to improve their wear resistance through metastable retained austenite, which has significant potential in demanding industrial environments. This scientific study examines the possibilities of increasing the economic efficiency of the production and use of AHSS steels in various industrial areas and at the same time reducing costs compared to expensive wear-resistant steels. A key aspect of the research is the experimental evaluation of heat treatment optimization to maximize resistance to mechanical damage and extend the life of materials in various applications.

Abstract: The production of high-quality and long-lasting products requires the application of materials with specific properties in their production. Therefore, the share of application of materials with high hardness and strength has been increasing recently. This encourages many researchers to focus their development on materials with specific properties. These materials, which are characterized by specific properties, include sintered carbides. Therefore, research was conducted with the aim of obtaining relevant dependencies of the influence of the chemical composition of sintered carbides with a Co binder on their selected mechanical properties. As part of the research, significant dependencies of the influence of the percentage of the Co bonding element in the sintered carbide as well as the grain size on its hardness, flexural strength and fracture toughness were obtained. It was found that with an increasing proportion of the Co bonding element, hardness decreases and at the same time flexural strength and fracture toughness increase. At the same time, with increasing grain size, hardness and flexural strength decrease, while fracture toughness increases. The obtained data also provide suitable data for optimizing the mechanical properties of sintered carbides and drawing complex conclusions in several important contexts.

Abstract: This study investigates the effectiveness of carbon nanotubes (CNTs) in enhancing the surface hardness of mild steel through carburization. CNTs were synthesized via chemical vapor deposition at 700°C using iron nitrate and cobalt nitrate as precursors on CaCO₃ support. Acetylene was used as the carbon source and nitrogen as the inert gas. The as-synthesized CNTs were purified using a one-step nitric acid treatment. Characterization by SEM, TGA, and FTIR revealed CNT diameters of 42-52 nm and improved thermal stability after purification, with TGA showing mass losses of 78% for as-synthesized CNTs and 85% for purified CNTs. Low carbon steel (AISI 1018) samples were carburized with as-synthesized and purified CNTs at austenitic temperatures of 750°C and 800°C for period ranging from 10 to 50 minutes. The carburizing process involved heating at 10°C/minute, followed by a defined number of boost and diffusion steps. Surface hardness was evaluated using a Vickers FM 700 micro-hardness tester, and microstructure was checked with an Olympus SC50 optical microscope. Results show that the use of purified CNTs in the carburization displayed the highest surface hardness of 191.64 ± 4.16 GPa at 800°C for 50 minutes, representing a 32% increase over the untreated substrate (145.188 ± 2.66 GPa). As-synthesized CNTs yielded a hardness value of 177.88 ± 2.35 GPa under the same conditions. At 750°C, the percentage increase in hardness for as-synthesized CNTs and purified CNTs were 10.04% and 15.77%, respectively, compared to the untreated substrate. Higher carburization temperature and longer treatment time consistently increased the surface hardness. The use of purified CNTs resulted in an increase of 6.37% hardness when compared to that of the as-synthesized CNTs at 750°C. Microstructural changes in the steel samples confirmed improved surface hardness with both purified and unpurified CNTs, with purified CNTs showing superior performance. This study therefore provides a platform for the use of CNTs for enhancing surface hardness of steel for various industrial applications requiring enhanced mechanical properties and wear resistance in low carbon steels.

Abstract: This research investigated the magnesium (Mg), silicon (Si) content, and aging temperature's effect on the microstructure and hardness of Al-Mg-Si alloys using Response Surface Methodology (RSM). The study varied Mg content between 0.4% and 1%, Si content from 0.4% to 0.8%, and aging temperatures between 170 °C to 210 °C. The findings revealed that increasing the Mg content from 0.85% to 1% and optimizing aging temperatures between 180 °C and 195 °C significantly improved hardness, primarily due to the enhanced formation of magnesium silicide precipitates (Mg₂Si). In contrast, lower Mg levels of 0.4%, Si content below 0.42%, or aging temperatures lower than 170 °C or higher than 200 °C resulted in reduced hardness. This reduction in hardness is linked to the limited precipitation of Mg₂Si, which diminishes the obstacles to dislocation movement.

Abstract: Sterling silver commonly uses copper as its primary alloying element, which enhances hardness. However, the presence of copper can cause a fire stain—a red spot microstructure—leading to tarnishing issues. This research focuses on reducing the copper content and developing suitable processes to enhance hardness through the use of three different alloy compositions within the AgCu and AgCuZnNi systems: Alloy SA (92.5 wt% Ag - 7.5 wt% Cu), Alloy A (93.5 wt% Ag - 5.01 wt% Cu - 0.79 wt% Zn - 0.70 wt% Ni), and Alloy B (94.5 wt% Ag - 4.24 wt% Cu - 0.63 wt% Zn - 0.63 wt% Ni). Precipitation hardening was measured at temperatures of 250 °C, 350 °C, and 450 °C for various durations ranging from 15 to 180 minutes. The results demonstrated an improvement in hardness, increasing from 60-70 HV to 120-160 HV after the heat treatment, with optimal results achieved for Alloy B at a temperature of 350 °C for one hour. This refined alloy composition presents a viable alternative, offering reduced copper content while maintaining enhanced mechanical strength and long-term durability post-heat treatment. Furthermore, the CIELAB test confirmed that Alloy B exhibits superior tarnish resistance. The composition and optimized process outlined in this research can serve as a guideline for producing sterling silver for commercial applications.