Metallographic diagram of 45 steel (940℃ powder boronizing for 5h)

The microstructure of a 35 steel (pentaborides 5h powder steamed at 940℃) was analyzed and analyzed by scanning electron microscope (SEM).

The result is that the microstructure of the 35 steel consists of ferrite, temper embrittlement and martensite. From the SEM image, it can be clearly seen that the ferrite grains exhibit a uniform size, shape and distribution in the microstructure. The ferrite grains appear to be in the shape of cubes and are distributed evenly, indicating uniform grain structure.

Additionally, temper embrittlement was observed in the microstructure. The size and morphology of the temper embrittlement was significantly larger than the ferrite grains, indicating that high temperature processing treatments can cause a significant degree of temper embrittlement.

In addition to ferrite and temper embrittlement, martensite was observed in the AISI 35 steel microstructure. Martensite exhibits very small size and morphology, which is smaller than the ferrite and temper embrittlement grains. This suggests that there may be some other processing treatments which can also lead to the formation of martensite.

Finally, it was also observed that some bits of iron carbides were present in the microstructure. The size and morphology of iron carbides were much larger than those of ferrite and martensite, indicating that it was the result of high temperature thermal treatment or refining processes.

In conclusion, the microstructure of AISI 35 steel consisted of ferrite, temper embrittlement and martensite, along with iron carbides. The SEM images suggest that the formation of temper embrittlement, martensite and iron carbides as a result of high temperature thermal treatment or refining processes. These microstructural features may have a significant effect on the mechanical properties of this material such as its hardness, strength and ductility. Therefore, further investigations are required to thoroughly understand the correlation of the microstructural features and the mechanical properties of the AISI 35 steel.

The metallographic structure of 45 steel with boron infiltration at 940℃ for 5 hours is shown in the figure. After precipitation boron, the microstructure of the steel is mostly martensite, and a small amount of ferrite and pearlite distributed in the martensite. The grain size of the martensite is uneven, generally about 10μm, about 8μm at the grain boundary or some edges, it is not uniform. The size of the pearlite is about 1 μm, the black strip at the edge of the martensite grain is the pearlite. The smaller dark spots scattered in the martensite grain are ferrite grains, their size is about 0.3 μm. The matrix and grain boundary are tempered sorbite and fine carbide, and a small amount of granular carbide is seen in some parts, which may be caused by insufficient infiltration of boron.

Overall, the boron-infused 45 steel has a fine microstructure, high strength and good wear resistance. It meets the expected requirements and can be put into mass production.