Analysis of the Effect of Vegetal and Coking Coals on the Surface Hardness of Carburized Aisi 8620 Steel

In this investigation was developed a comparative study of the superficial hardness of AISI 8620 steel thermally treated by carburizing, by the use of vegetable and coking coals. The objective was to propose an alternative to the element used to generate the carburizing atmosphere. The previous stages have been described, such as the preparation of the material and its verification, as well as the dimensions and characteristics, defined by the ASTM E-18 standard. By considering four variables, each one with two levels, an orthogonal array matrix of 16 experiments was generated. The surface hardness measurements were processed through an analysis of variance (ANOVA), where the significance of each variable considered as a factor was obtained. Coking coal can be used as an element for the generation of carburizing atmosphere since a maximum relative error of 3.86% was obtained between the experimental values and the values in the literature. In contrast, the vegetable coal did not improve the mechanical properties of the steel, reaching an average hardness of 25.95 HRC after heat treatments.