Mechanical properties of the CO2 free vacuum carburized in SCM415H

Vacuum carburizing is supposed to be the superior process to the gas carburizing. However, the vacuum carburizing has the stage in which hydrocarbon gas is supplied into the furnace to be pyrolysis, and consequently the stable heat treatment is hard to achieve due to the soot from the hydrocarbon pyrolysis. Recently, many studies have been made which utilize acetylene gas to overcome this defects. In this paper, the carburizing and the diffusion periods have been selected based on the Harris experimental formula, and the mechanical properties of the vacuum carburized specimen have been compared with those of the gas carburized SCM415H specimen to identify the feasibility of the CO2 free vacuum carburizing process. The result showed that the vacuum carburized materials used have no oxidization of the grain boundaries, and show the 29.8% higher effective hardness depth and the acceptable tensile strength