In-situ carburized coating produced by reactive plasma spraying of low carbon steel using methane

In the present investigation, an in-situ carburized coating was produced by reactive plasma spraying of low carbon steel using 100% methane as powder carrier gas. Microstructural and chemical analysis revealed modification of the microstructure and a significant increase in carbon content from 0.13 to > 1 wt.% C in the reactive plasma sprayed low carbon steel. Micro-hardness of the reactive plasma sprayed low carbon steel coating (707 ± 26 HV) was about three times higher than that of the non-reactive plasma sprayed low carbon coating (245 ± 11 HV). A Langmuir adsorption model was used to study the interactions that occur between the steel particles and the gaseous carbon environment. Accordingly, the thermal and momentum fields of a steel particle along the reactive plasma gas jet were numerically simulated. These simulations revealed a calculated particle carbon content in the range of 1–4 wt.% C, which corresponded to an order of magnitude agreement with the measured results. The experimental and numerical results obtained in this study suggest that the physical adsorption of gaseous carbon onto the steel particles was significant during reactive plasma spraying.