Abstract
In this research, (MOORA) approach based– Taguchi design was used to convert the multi-performance problem into a single-performance problem for nine experiments which built (Taguchi (L9) orthogonal array) for carburization operation. The main variables that had a great effect on carburizing operation are carburization temperature (oC), carburization time (hrs.) and tempering temperature (oC). This study was also focused on calculating the amount of carbon penetration, the value of hardness and optimal values obtained during the optimization by Taguchi approach and MOORA method for multiple parameters. In this study, the carburization process was done in temperature between (850 to 950 ᵒC) for 2 to 6 hours. Quenching was done for the specimens after heat treatments in furnace chamber by using different quench solutions, water, salt and polyvinyl alcohol. Analysis of variances - (ANOVA) were performed for nine experiments in order to optimize the problem that was associated with multiple criteria (parameter) to achieve maximum hardness and depth penetration. The program results showed that the optimum conditions are carburization temperature (950 oC), carburization time (2 hrs.), tempering temperature (200oC), tempering time (10 hrs.), and activator (10 wt. %). Furthermore, the best quenching media was the polyvinyl alcohol.
Highlights
Alloys of iron and carbon are known as steel which their definite content of carbon with the range of (0.15-1.5 %) [1], Steel alloys with low percentage of carbon have similarity properties of iron, as the percentage increase the metal acquires hardness and becomes stronger but less ductile [2], hardness is increased in the outer layer of metal surface by a series of processes known as case hardening and there are several methods of hardening one of them called carburizing, which is considered as a very important process and it is performed to steel surface hardening [3, 4]
MOORA-based Taguchi’s design method can be used to determine the optimal carburization parameters for the carbon steel alloy studied in the paper
It was found that: 1. The (MOORA) method was applied to determine the most optimum conditions for carburizing process of steel and the results show that the optimum conditions are, carburization temperature (950 operation are carburization temperature (oC)), carburization time (2 hrs.), tempering temperature (200 oC), tempering time (10 hrs.), activator (10 wt. %) and quench media polymer to get the optimum results for the carburizing
Summary
Alloys of iron and carbon are known as steel which their definite content of carbon with the range of (0.15-1.5 %) [1], Steel alloys with low percentage of carbon have similarity properties of iron, as the percentage increase the metal acquires hardness and becomes stronger but less ductile [2], hardness is increased in the outer layer of metal surface by a series of processes known as case hardening and there are several methods of hardening one of them called carburizing, which is considered as a very important process and it is performed to steel surface hardening [3, 4]. The crystals structure of steel can be determined by atomic arrangement. There are two crystal structures of iron; one of them is bodycentered-cubic (BCC) and the other is the facecentered-cubic (FCC), the (FCC) atomic arrangement of structure have high solubility limit than a (BCC) structure, which belongs to the interstitial sites where carbon can sit between the iron atoms [6]. Surface hardening is a simple approach of hardening of the steel surface. This technique is used for low carbon steels, where the carbon is added to the external surface of the steel [8]. The process is generally done within austenitic range at temperature between (850-950 oC) for mild
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