جستجوی مقالات مرتبط با کلیدواژه "wear resistance" در نشریات گروه "مکانیک"

The aim of this study is to achieve an optimal chemical composition in the metal matrix composite (MMC) (Fe-C-Cu-SiC) to enhance the wear resistance of the composite and evaluate its mechanical properties based on the optimal amount of copper, making it suitable for use in brake pads for aircraft, locomotives, and racing cars. For this purpose, Fe, C, and BaSO₄ with a chemical composition of (6SiC-6.5C-6BaSO₄-Fe) and varying amounts of copper (3%, 7%, 11%, 15%, and 19%) were mechanically milled using powder metallurgy. The materials were then sintered in a furnace with protective gas and hot-pressed at 1000°C and 400 MPa, resulting in five test samples. Wear and friction coefficient tests were conducted under a load of 20 N, at 700 rpm, over a distance of 1000 m. Hardness tests, density measurements, microstructural examination with a scanning electron microscope (SEM), and EDAX analysis were also conducted to assess the wear mechanism. Examination of the worn surfaces indicated that during the initial sliding distance, the predominant mechanism was abrasion. As the sliding distance increased, abrasive and oxidation wear mechanisms, along with plastic deformation, became active. Test results showed that the Fe-15Cu-6.5C-6SiC-6BaSO₄ sample had higher wear resistance and a more suitable friction coefficient (within the acceptable range of 0.2 to 0.4) compared to the other four samples, suggesting its potential application for brake pads.

Nowadays, Aluminum alloys are chosen for various industrial applications due to their special properties and high corrosion resistance. By optimizing the surface properties of Aluminum alloys, the performance and reliability of using these materials can be effectively improved. Therefore, investigating the surface mechanical treatment has been the focus of researchers and various mechanical methods have been used to improve the surface characteristics of Aluminum alloys. Among these methods, ultrasonic hammer peening is a cold work process in which many impacts are applied to the surface of the sample in a short period with high frequency. In this research, the effect of ultrasonic hammer peening on the wear properties of Aluminum alloy Al6061-T6 has been investigated. To carry out the process of ultrasonic hammering, three parameters of vibration amplitude, rotational speed of the work piece, and feed rate of the tool were selected and their effect on the wear resistance was investigated. The obtained results showed that the ultrasonic hammer peening increased the surface hardness by about 141.4%. With the increase of the vibration amplitude and the feed rate, the wear resistance increased and the increase of the rotational speed decreased the wear resistance. The highest wear resistance has been obtained in the vibration amplitude of 11 µm, rotational speed of 500 rpm, and feed rate of 0.8 mm/rev. As a result, the wear resistance has increased by about 46% compared to the raw material in these conditions.

In this research, two types of composite coatings based on epoxy paint reinforced by TiO2 nano and micro particles and TiO2 particles hydrophobicized by polysiloxane were prepared separately with concentrations of 1, 2, 3, 4 and 5% by weight to improve the properties of epoxy paint. and in order to investigate their behavior, they were applied on API 5L X52 steel and then their properties were investigated by conducting corrosion and wear tests. The thickness of the coatings was checked by a digital thickness gauge. The corrosion resistance behavior of the coatings was evaluated using the polarization method in 3.5% NaCl solution. The results of the corrosion test showed that by adding and increasing the concentration of reinforcing particles in the coatings, the corrosion resistance was improved, and also the composite coating of epoxy paint with 5% by weight of the hydrophobic TiO2 reinforcement showed better corrosion resistance than other samples. A scanning electron microscope (SEM) equipped with EDX was used to examine the morphological properties of the surface. In order to check the dispersion of micro particles in the field of coating, Map analysis was taken from the samples. The results obtained from Map analysis have shown the appropriate and uniform distribution of hydrophobic particles in the field of epoxy coating. The wear resistance of the coatings was performed by the bullet test machine on the disc. The results of the abrasion test showed that by adding and increasing the concentration of reinforcing particles in the coating, the abrasion resistance of the coating increased, but by comparing the epoxy composite samples, it was found that the hydrophobicity of the reinforcing particles had no effect on the abrasion resistance.

Friction stir processing is widely used for improvement of properties and microstructure of Aluminum, Copper and Magnesium alloys but investigation on steels are limited. Due to the fact that steel alloys, in addition to aluminum, copper and magnesium alloys, have good engineering properties and vast applications in the industry, they need to be processed by friction-stirring process. In this regard, the present research examines the effect of frictional stirring process on grain size, hardness and wear resistance of Ck45 steel due to the number of passes and tool design. In this research, it was shown that the friction-stirring method can be an effective method to increase the hardness and wear resistance of this steel in such a way that increasing the number of passes causes more heat generation per unit length and also affects the grain size, hardness and probably atomic penetration. In general, with the increase in the number of passes, the size of the grains in the stirring area becomes larger, while the final hardness and wear resistance are determined under the joint effects of grain size and hardness. The results indicate that the hardness has increased by 42% and the amount of wear has decreased by 85% compared to the original sample by the frictional stirring process.Keywords

In this study, surface transformation hardening of AISI O1 cold work tool steel was investigated by use of a high power (1600 W) diode laser apparatus. In order to evaluate the effect of laser hardening, different output powers and scanning rates were applied and microstructures and phases were characterized, as well as micro-hardness and wear resistance were measured. The hardening treatment resulted in formation of a hardened zone of about 2 mm depth and up to 10 mm width at the surface of sample. The microstructure of this hardened zone was comprised of martensite and residual austenite; average surface hardness of the samples treated under various set of variable parameters was 650 to 760 Vickers. Increase of heat input caused increase of residual austenite content and formation of coarse martensite structure so that the least hardness was obtained for the sample processed by the highest heat input. Comparing wear resistance of laser hardened samples with traditionally quench-temper hardened and annealed specimens, it was revealed that the laser hardening process improves wear resistance of hardened samples so that wear resistance of the samples hardened via laser was about 10 times of the annealed ones.

In this research, electroless nanocomposite coating of Ni-P-SiO2-MoS2 and effect of SiO2 and MoS2 nanoparticles on microstructure and wear resistance of coating were investigated. First of all, samples from MO40 (AISI 4140) steel sheet were prepared and coated in Nickel-Phosphorous electroless bath containing 7 g/l SiO2 and MoS2 particles in 90°C and 6.4 pH for 60 minutes. Then, pin on disk wear test was performed to evaluate the wear resistance of the coated and uncoated samples. Several experiments used to explore tribological features of deposited electroless coatings. Field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS) images were taken to investigate coating microstructure and its elements, respectively. Microstructural results showed that a uniform coating on substrate was successfully composed. Also, several mechanisms observed during the abrasion process. Abrasive and adhesive mechanisms were active in uncoated samples, but by applying SiO2 and MoS2 nanoparticles, the sliding mechanism was activated. Furthermore, with decreasing friction coefficient, wear resistance increased by 79.3% and also the tribological properties of the sample improved.

Nowadays, many attempts have been made to replace conventional materials with polymers which have the advantage of having less weight and higher formability. Polymers besides these advantages have some shortcomings. One method to overcome these shortcomings is to strengthen them by adding other materials to polymers. As an example, polymer nanocomposites are made by adding nanoparticles to polymers to enhance their tribological performance. In this paper, an experimental and numerical study on the correlation between temperature rise and the wear rate in the polyethylene (PE) with 10% ZnO nanoparticles has been investigated. A comparison between pure PE and polymer nanocomposite has been made. A 3D finite element model has been developed in Abaqus to study the wear in the contact of pin and the disk. The results predicted by the FE model are compared to the experimental data obtained in this research using the pin on disk test rig. According to the results, a non-linear relation between temperature changes and wear rate has been developed.

In this research, 3 layer composite weld containing Titanium diboride (TiB2) on low carbon steel (ST37) was carried out through flux cored arc welding via flux cored electrodes containing 100% TiB2 and 50-50 TiB2-Fe. Then, wear and microhardness tests were used for surviving hardness and wear behavior of samples. The obtained results showed that by increasing volume percent of TiB2 in microstructure, the hardness of layers increased. Also, the highest wear resistance belonged to third layer of sample with 50% TiB2 and thereafter, belonged to first layer of sample with 100% TiB2. The scanning electron microscopic investigation of samples wear surfaces indicated that by increasing volume fraction of TiB2 into layers, the depth wear scratches in the third and second layers decreased and segregation of wear debris in these layers increased, compared with first layer. Also, it was found that by increasing the layers, wear mechanism changed from ploughing to cutting.

Ti-6Al-4V titanium alloy has great application in medicine and military industries due to its capabilities, namely high strength to weight ratio and corrosion resistance. In the current research, the effect of aging treatment on microstructure and wear behavior of Ti-6Al-4V titanium alloy was investigated. Pin on disk wear test was applied to assess the wear behavior. Specimens were first solution treated at 950C and 1050C and then were quenched and aged. Some specimens were annealed before aging at 700C. The results showed that aging treatment resulted in the hardness increase and the wear resistance decrease. It was also observed that annealing treatment before aging, enhanced the martensite decomposition and the formation of α2 particles, and correspondingly resulted in more hardness and lower wear resistance. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses confirmed that presence of hard phase α2 particles within soft beta phase was the main reason for wear resistance decrease.

Engineering components during service are exposed to destructive phenomena such as wear which may lead to their destruction. For their protection and reduction of costs of replacement of these defective components and also increasing productivity, attention is given to welding processes for depositing a wear-resistant layer on the components. In this research, the effect of welding current on last layer weld quality deposited on carbon steel by shielded metal arc welding process using Fe-based hardfacing electrodes is investigated. The chemical composition of the weld deposit layers was studied by quantometery. Optical and scanning electron microscopes, energy dispersive X-ray fluorescence and X-ray diffraction were used for microstructural studies. Microhardness and pin on disk wear tests were also employed for microhardness and wear resistance evaluations. The metallography and X-ray diffraction results show presence of martensite and retained austenite in the microstructure of the last deposited weld layer. The results of chemical analysis and microhardness and wear-resistant tests show that increasing the current increases weld dilution which leads to reduction of alloying elements affecting hardness and wear resistance of the weld deposit and hence these properties decrease slightly. Evaluation of the worn surfaces shows that the wear mechanism on the last deposited layer is of abrasive wear type.