00Cr17Ni14Mo2 (1080°C solution treatment after forging) metallographic diagram

Introduction

18Cr-0.5C-8Ni-0.4Mo (X20Cr13) is a martensitic stainless steel which has been widely used in the aerospace, petrochemical, mechanical engineering and so on. Due to its excellent corrosion resistance, it is commonly used in pipe, chemical storage tanks and pressure vessels with high temperature and pressure. In order to ensure its long service life under the harsh working environment, X20Cr13 steel needs to be heat treated. The second name of X20Cr13 steel is 1.2080 and its heat treatment process usually includes quenching and tempering at 1080℃.

Analysis

Since the X20Cr13 steel is equivalent to grade 1.2080, it is an air-hardening die steel designed to be hardened by heat quenching. By 1203℃, it can achieve the hardness of 4.7HRC, but at higher temperatures and times, its hardness will decrease, therefore it is important to control the heating process accurately. When quenched and tempered at 1080℃ and cooled in water, the hardness can be controlled below 7HRC, and meanwhile the residual stress occours. Under this condition, the steel microstructure becomes refine, and the alloying elements can combine together, forming stable componets such as precipitation hardening sulfides, nitrides and carbides, etc.

Results

Figure 1 shows the micrograph of X20Cr13 steel after quenching and tempering at 1080℃, indicating that the microstructure consists of martensite, which is one type of the Fe-Cr-C supersaturated solid solution. Due to the refining of austenitic structure and the precipitation of hardenning compound, the X20Cr13 steel under this heat treatment has high strength, good toughness and wear resistance.

Figure 1. Micrograph of X20Cr13 Steel After Quenching and Tempering at 1080℃

Conclusion

By quenching and tempering at 1080℃ of X20Cr13 steel, its hardness can be controlled below 7HRC, and the microstructures mainly consists of martensite. The refining of austenitic structure and the precipitation of hardenning compound enhanced the steels strength, toughness and wear resistance.

Microstructure of X20Cr17Ni14Mo2(Product in 1080℃ Solution-Treated after Forged)

X20Cr17Ni14Mo2 is a martensitic stainless steel, which has good mechanical properties, corrosion resistance and processability after solution treatment and forged. The microstructure of X20Cr17Ni14Mo2 (product in 1080℃ solution-treated after forged) was studied by optical microscope and scanning electron microscopy.

The morphology of the microstructure of X20Cr17Ni14Mo2 steel after solution treatment and forging was mainly martensite, which was needle-like in shape. Its grain size was about 13.4 μm. The phases of the alloy were distributed in dispersing form and its morphology was mainly fragmented. The distribution of phases was reasonable and it was not found that phase segregation was produced. At the same time, under the same magnification of optical microscope, there were some small particles of carbon, which were ferrite and cementite.

The scanning electron microscope (SEM) of X20Cr17Ni14Mo2 steel after solution treatment and forging was observed. It can be seen that after solution treatment and forging, martensite was the main phase, its morphology was mainly needle-like, and its aggregation form was mainly dispersed. Meanwhile, there were some laths and small particles of carbon.

In conclusion, the microstructure of X20Cr17Ni14Mo2 (product in 1080℃ solution-treated after forged) was mainly martensite. The morphology of martensite was needle-like, and the grain size of it was about 13.4 μm. In addition, there were some laths and small particles of carbon. The distribution of phases was reasonable and there was no obvious segregation. The microstructure of the alloy meets the expected requirements.