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    • Selection of coating material for magnesium alloy using Fuzzy AHP-TOPSIS

      RESMI V PRASAD R RAJESH D THIRUMALAIKUMARASAMY

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      Magnesium alloys are inherently negative electrochemical potential and are very reactive compared to other engineering metals. They are prone to galvanic corrosion and micro cracks. Various coating materials or Alternatives and the required criteria and sub-criteria for the selection of Alternatives for AZ31B magnesium alloy substrate are identified by means of literature review. Criteria weight and the rank of the alternatives are usually vague and hence uncertainty prevails. The best Alternative from several potential ‘‘Candidates’’, subjectto several criteria and sub-criteria, needs to get decided. In such cases, multi criteria decision making (MCDM) techniques help in determining the MOST suitable coating material. This paper concentrates on the selection ofcoating material for the magnesium alloy substrate. The problem is subjective, uncertain and equivocal in nature. Hence in this study, fuzzy analytic hierarchy process (AHP) is applied to obtain the weights of criteria and technique for order performance by similarity to ideal solutions (TOPSIS) is utilised for ranking theAlternatives.

    • Sensitivity analysis and optimisation of HVOF process inputs to reduce porosity and maximise hardness of WC-10Co-4Cr coatings

      RESMI V PRASAD R RAJESH D THIRUMALAIKUMARASAMY S VIGNESH S SREESABARI

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      This paper aims at developing an empirical relation to predict the porosity and micro-hardness, by means of High Velocity Oxy Fuel (HVOF) sprayed WC-10Co-4Cr coatings. For determining the coating performance, process parameters such as flow rate of LPG fuel, flow rate of oxygen, spray distance, flow rate ofcarrier gas and feed rate of the coating powder play a significant role. Five-factors, five-level central composite rotatable design (CCD) was employed in this analysis to reduce the number of experiments by covering all possible combinations of the process variables. A mathematical model was established to assess the porosity and microhardness of the coatings including HVOF process parameters and the appropriateness of the model was examined using analysis of variance. Using RSM, process parameter optimizations were conducted. Thecoatings produced using optimized process variables had a minimum porosity level of 0.2 Vol. percentage and a maximum hardness of 1325.26 HVx compared to other coatings. This has been confirmed by the developing response graphs and also by plotting contours. The optimization of HVOF parameters using RSM, as well as the correlation of spray variables with properties of the coating, enables the recognition of the framework of the characteristics to attain the preferred consistency of WC-10Co-4Cr coatings. Analysis of Sensitivity is alsoperformed to determine the most significant process parameter for the HVOF operation.

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