ارزيابي ريز ساختار و رفتار سايشي پوشش كامپوزيتي استاليت 6 بر سطح فولاد ساده كربني به روش جوشكاري تنگستن-گاز پالسي

چكيده انگليسي :

Evaluation of Microstructure and Wear Resistance of Stellite6 Tungsten Carbide Cladding by Pulse Current Gas Tungsten Arc Welding Farhad Madadi F madadi@ma iut ac ir Department of Materials Engineering Isfahan University of Technology Isfahan 8415683111 Iran Degree M Sc Language Farsi Supervisor Morteza Shamanian mshamanian@cc iut ac ir Fakhreddin Ashrafizade ashrafif@cc iut ac ir Abstract The main behaviour of this research is the study on microstructure hardness dilution phase formation wear behaviour fracture toughness and bending strength of stellite composite cladding on carbon steel with and without reinforcement in two pulsating and continuous current mode Mixtures of Stellite alloy powders and and tungsten carbide WC powders were used as the coating materials The process of welding was gas tungsten arc welding GTAW The microstructures of these coating were studied by optical microscopy scanning electron microscopy SEM and X Ray Diffraction XRD The specimens were characterized by energy dispersion spectroscopy EDS and micro hardness test and for bending strength a three point bending machine was used Wear tests were carried out using pin on disk method The worn surfaces were examined by scanning electron microscopy Results showed that the micro structures of these claddings include chromium carbides phases dispersed in the matrix of the Co based alloy with dendritic structure The hardness of specimen with tungsten carbide WC and claded in pulsating mode was higher than other specimens The surface hardness of specimen with tungsten carbide WC was near HV The dominant mechanism of wear test was abrasive with some adhesive wear The weight loss of the specimen with increase in weight fraction of reinforcement decrease Coefficient of friction for satellite without tungsten carbide WC was measured between Use of pulsating current mode decreased the dilution of iron because of decrease in the amount of heat input Toughness of stellite withoute reinforcement was higher than other specimens The added tungsten carbide WC was completely melted into the weld pool and the resolidified structure contained Co CoCr and some types of carbides It was indicated that the use of pulsed current leads to a decrease in dilution and formation of a finer microstructure having higher hardness Several significantly different solidified microstructures were characterized by dendrites eutectics and faceted dendrites in the claddings The faceted dendrites contained the majority of W as well as Cr and Co while the matrix had higher Cr and Co content The presence of faceted dendrites caused improvement in wear behavior of claddings with more tungsten carbide WC content introduced more faceted dendrites was obtained This study highlights the experimental study carried out to develop mathematical models to predict dendrite arm spacing and hardness of the cladding overlay The experiments were conducted based on four factor five level central composite rotatable design with full replication technique and the mathematical models were developed using multiple regression method The developed models have been checked for their adequacy and significance by ANOVA technique The optimum conditions for pulse TIG cladding process and optimum hardness and dendrite arm spacing values for cladding of cobalt base alloy on mild steel were found and checked with ANOVA technique The results were confirmed using conformity tests and found to have a good accuracy Keywords Stellite 6 composite Microstructure Gas Tungsten Arc Welding Pulse current Wear Fracture toughness

مددي، فرهاد

ارزيابي ريز ساختار و رفتار سايشي پوشش كامپوزيتي استاليت 6 بر سطح فولاد ساده كربني به روش جوشكاري تنگستن-گاز پالسي

روكش كاري قوس تنگستن-گاز , جريان پالسي , چقرمگي شكست و طراحي آزمايش