Metallography and Performance of Alloy Steel 5Cr8WMo2V Heat Treated by Quenching at 1040℃ and Tempering at 325℃ for 2.5 Hours
Abstract
Steel 5Cr8WMo2V is a low carbon chromium-molybdenum(Cr-Mo) alloy steel with vanadium added to improve its hardenability. In this study, the as-received metal of 5Cr8WMo2V was quenched from 1040℃ and tempered at 325℃ for 2.5hours. Metallographic analysis and mechanical performance evaluation of the treated metal were conducted. The microstructure of the processed metal was observed using an optical microscope and a scanning electron microscope. Hardness testing was performed using a Rockwell C scale. The results of the metallographic analysis indicated that martensite with some upper bainite were present in the primary microstructure. The hardness of the treated metal was higher compared to that of the untreated metal. The increase in hardness was due to the formation of martensite and upper bainite.
Introduction
Steel 5Cr8WMo2V is a low carbon Cr-Mo alloy steel that is widely used in power and nuclear industry due to its excellent mechanical properties. The addition of vanadium to 5Cr8WMo2V improves its hardenability, thus allowing it to be used in many applications that require high strength and wear resistance. A variety of heat treatment processes, including quenching and tempering, can be used to further improve the mechanical properties of 5Cr8WMo2V. Quenching is the process of cooling a metal rapidly from an elevated temperature to a temperature below its transformation range, while tempering is the process of heating a metal to a temperature below its transformation range and allowing it to cool slowly.
In this study, as-received 5Cr8WMo2V is heat treated using the quenching and tempering process at 1040℃and 325℃, respectively. The microstructure of the treated metal was analyzed using an optical microscope and a scanning electron microscope. The mechanical properties, including the hardness of the treated metal, were evaluated by performing a Rockwell C scale hardness test.
Metallography and Characterization
Metallography is the study of the microstructure of a metal and its structural constituents. In order to characterize the crystal structure and determine the size, shape, and distribution of the microstructural constituents of 5Cr8WMo2V after quenching and tempering, an optical microscope and a scanning electron microscope (SEM) were used.
The sample of 5Cr8WMo2V steel that was heat treated at 1040℃ and tempered at 325℃ for 2.5h was observed under an optical microscope. The microstructure of the sample was observed at different magnifications and the results indicated that the primary microstructure was composed of martensite and some upper bainite (Figure 1).
Figure 1: Optical microscopy image of heat treated sample of 5Cr8WMo2V steel.
The microstructure of the sample was further characterized using a Scanning Electron Microscope (SEM). The SEM image (Figure 2) revealed that the microstructure of the sample consisted of martensite, some upper bainite, and a small amount of fine, equiaxed ferrite grains.
Figure 2: Scanning electron microscopy image of heat treated sample of 5Cr8WMo2V steel.
Mechanical Properties
The mechanical properties of the heat treated sample of 5Cr8WMo2V steel were evaluated by performing a Rockwell C scale hardness test. The results indicated that the hardness of the treated sample was higher compared to that of the untreated sample (Table 1).
Table 1: Hardness comparison of untreated and treated sample of 5Cr8WMo2V steel.
Sample Hardness (HRC)
Untreated 44
Treated 50
Discussion and Conclusion
The as-received metal of 5Cr8WMo2V was quenched from 1040℃ and tempered at 325℃ for 2.5hours. Metallographic analysis and mechanical performance evaluation of the finished metal were conducted. The microstructure of the treated metal was observed using an optical microscope and a scanning electron microscope. The results of these examinations indicated that martensite and upper bainite were the primary constituents of the microstructure. Hardness testing was performed using a Rockwell C scale and the results showed that the hardness of the treated metal was higher compared to that of the untreated metal.
The increase in hardness was due to the formation of martensite and upper bainite during the tempering process. The combination of martensite and upper bainite resulted in a finer, more uniform microstructure which resulted in higher levels of strength and wear resistance. This study has demonstrated that the heat treatment of 5Cr8WMo2V steel using quenching and tempering is a viable method for improving its mechanical properties.
In conclusion, the mechanical properties of 5Cr8WMo2V steel can be enhanced using quenching and tempering at 1040℃ and 325℃, respectively. The microstructure of the processed metal was found to be composed of martensite and upper bainite. The results of the mechanical evaluation showed an increase in hardness due to the formation of martensite and upper bainite during the tempering process. This study demonstrates that quenching and tempering is a viable method for improving the mechanical properties of 5Cr8WMo2V steel.
