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Abstrakt

The AISI 430 stainless steel with ferritic structure is a low cost material for replacing austenitic stainless steel because of its higher yield strength, higher ductility and also better polarisation resistance in harsh environments. The applications of AISI 430 stainless steel are limited due to insignificant ductility and some undesirable changes of magnetic properties of its weld area with different microstructures. In this research, a study has been done to explore the effects of parameters of laser welding process, namely, welding speed, laser lamping current, and pulse duration, on the coercivity of laser welded AISI 430 stainless steel. Vibrating sample magnetometery has been used used to measure the values of magnetic properties. Observation of microstructural changes and also texture analysis were implemented in order to elucidate the change mechanism of magnetic properties in the welded sections. The results indicated that the laser welded samples undergo a considerable change in magnetic properties. These changes were attributed to the significant grain growth which these grains are ideally oriented in the easiest direction of magnetization and also formation of some non-magnetic phases. The main effects of the above-mentioned factors and the interaction effects with other factors were evaluated quantitatively. The analysis considered the effect of lamping current (175-200 A), pulse duration (10-20 ms) and travel speed (2-10 mm/min) on the coercivity of laser welded samples.
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Abstrakt

The wear behaviour of Cr3C2-25% NiCr laser alloyed nodular cast iron sample were analyzed using a pin-on-disc tribometer. The influence of sliding velocity, temperature and load on laser alloyed sample was focused and the microscopic images were used for metallurgical examination of the worn-out sites. Box-Behnken method was utilised to generate the mathematical model for the condition parameters. The Response Surface Methodology (RSM) based models are varied to analyse the process parameters interaction effects. Analysis of variance was used to analyse the developed model and the results showed that the laser alloyed sample leads to a minimum wear rate (0.6079×10–3 to 1.8570×10–3 mm3/m) and coefficient of friction (CoF) (0.43 to 0.53). From the test results, it was observed that the experimental results correlated well with the predicted results of the developed mathematical model.
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Abstrakt

The development of industry is determined by the use of modern materials in the production of parts and equipment. In recent years, there has been a significant increase in the use of nickel-based superalloys in the aerospace, energy and space industries. Due to their properties, these alloys belong to the group of materials hard-to-machine with conventional methods. One of the non-conventional manufacturing technologies that allow the machining of geometrically complex parts from nickel-based superalloys is electrical discharge machining. The article presents the results of experimental investigations of the impact of EDM parameters on the surfaces roughness and the material removal rate. Based on the results of empirical research, mathematical models of the EDM process were developed, which allow for the selection of the most favourable processing parameters for the expected values of the surface roughness Sa and the material removal rate.
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Abstrakt

The dry sliding wear behavior of heat-treated super duplex stainless steel AISI 2507 was examined by taking pin-on-disc type of wear-test rig. Independent parameters, namely applied load, sliding distance, and sliding speed, influence mainly the wear rate of super duplex stainless steel. The said material was heat treated to a temperature of 850°C for 1 hour followed by water quenching. The heat treatment was carried out to precipitate the secondary sigma phase formation. Experiments were conducted to study the influence of independent parameters set at three factor levels using the L27 orthogonal array of the Taguchi experimental design on the wear rate. Statistical significance of both individual and combined factor effects was determined for specific wear rate. Surface plots were drawn to explain the behavior of independent variables on the measured wear rate. Statistically, the models were validated using the analysis of variance test. Multiple non-linear regression equations were derived for wear rate expressed as non-linear functions of independent variables. Further, the prediction accuracy of the developed regression equation was tested with the actual experiments. The independent parameters responsible for the desired minimum wear rate were determined by using the desirability function approach. The worn-out surface characteristics obtained for the minimum wear rate was examined using the scanning electron microscope. The desired smooth surface was obtained for the determined optimal condition by desirability function approach.
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Abstrakt

The present investigation has been made to assess the influence of B4C reinforced with Ti-6Al-4V matrix prepared by powder metallurgy route. High energy ball milling was used to prepare the composites. Cylindrical preforms were prepared using suitable die set assembly. The green preforms were sintered in the muffle furnace at 900°C for 1 h. Further the preforms were cooled inside the furnace till the room temperature has attained. SEM with EDS mapping analysis was used to evaluate the morphology and elemental confirmation of the prepared composite. The density and hardness of the samples are determined using Archimedes principle and Rockwell hardness testing machine. The wear resistance of the samples was determined by employing a pin on disc apparatus. The hardness of the composites (Ti-6Al-4V /10B4C) was increased while comparing to the base material (Ti-6Al-4V) which is attributed to the presence of hard ceramic phase. Response Surface Methodology (RSM) five level central composite design approach was accustomed and it minimised the amount of experimental conditions and developed mathematical models among the key process parameters namely wt. % of B4C, applied load and sliding distances to forecast the abrasive response of Specific Wear Rate (SWR) and Coefficient of Friction (CoF). Analysis of variance was used to check the validity of the developed model. The optimum parameters of specific wear rate and coefficient of friction were identified.
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