Introduction
Metal alloys are an important part of metal metalurgy. 38CrMoAl is an alloy containing 38% chrome, 4% molybdenum, and 4% aluminum. This alloy is known for its superior hardness and strength when heat treated. The purpose of this experiment is to determine the effect of gas carburizing temperature on the microstructure of 38CrMoAl. In this experiment, 38CrMoAl bars were gas carburized at temperatures of 540°C for 30 minutes in nitrogen gas. After carburizing, the microstructures of the carburized samples were examined using an optical microscope.
Experimental Setup
The carburizing of the 38CrMoAl bars was conducted in a sealed stainless steel tube furnace under nitrogen gas flow. The furnace was heated up to a temperature of 540°C and the carburizing process was conducted for 30 minutes. The rates of the carburization reaction were monitored using a thermocouple.
Analysis
The microstructure of the carburized 38CrMoAl samples were examined under an optical microscope. The as-received sample showed a mainly face-centered cubic structure with a fine grain size. After carburizing, the grain size was found to have increased, indicating that there was a grain growth effect during the heat treatment process. The grain size distribution of the samples before and after the carburizing process was obtained using a SEM-EDS analysis.
Results and Discussion
The grain size distribution of the carburized 38CrMoAl samples is shown in Figure 1. As seen in the graph, the as-received samples had a finer grain size compared to the carburized samples. This is indicative of the grain growth that took place during the carburizing process. The grain size of the carburized samples was found to be significantly larger than the grain size of the as-received samples. This indicates that the carburizing process had an effect on the grain growth of the alloy due to the temperature and carburizing medium used during the heat treatment.
The microstructure of the carburized samples is shown in Figure 2. The as-received samples showed a mainly face-centered cubic (FCC) structure, while the carburized samples showed a more homogenous structure. This indicates that there was a redistribution of atoms during the carburizing process and that the carburizing process had an effect on the microstructure of the 38CrMoAl alloy.
Conclusion
The results of this experiment demonstrate that gas carburizing at a temperature of 540°C for 30 minutes in nitrogen gas has an effect on the microstructure of 38CrMoAl. Grain growth is observed in the carburized samples and the microstructure becomes more homogenous. Further research should be done to investigate the effects of other carburizing temperatures and times on the microstructures of different metal alloys.
