Because vacuum carburization is a novelty in the field of steel heat treating, the goal of this work is to compare the method with the conventional method of gas carburization and evaluate the pros and cons of the two methods. The samples were carburized at temperatures of 950 °C and 1020 °C, and then quenched. Samples carburized with the gas method were quenched in preheated oil (60 °C) and samples carburized with the vacuum method were quenched in a stream of high-pressure nitrogen gas (1 MPa). The goals of the heat treatment process were to reach minimal industrial standards for 18CrNiMo7, which are case depth of 1,5 mm and surface hardness of at least 60 HRC. Higher surface hardness (65 HRC) was reached in the sample carburized at 950 °C with the gas carburization process (P950) and in the sample carburized at 1020 °C with the vacuum process (V1020). The sample carburized at 950 °C with the vacuum process (V950) and carbon potential 1 m% showed a reduced surface hardness, as a result of oversaturation with carbon. Microstructural analysis later showed the formation of a carbide net on the surface of the sample. Even after extensive research, the industrial standards and parameters for vacuum carburization are not yet known, so we compared the effect of 1 m% carbon potential between the two methods. The biggest case depth proved to develop in sample V1020, that was carburized at a higher temperature. After analyzing process parameters, it was discovered that the process of vacuum carburization is more resource, energy and time efficient. At the same process temperature, vacuum carburization can be up to 40 % faster. At elevated temperatures that the conventional process of gas carburization cannot achieve, this difference can even reach 60 %. As vacuum carburization process is done at a very low partial pressure of carbon carrying gasses, without the presence of oxygen, the temperature of the process can be increased beyond 950 °C without fear of nitrogen decomposition or the formation of an oxide layer.
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