Metallographic diagram of 45 steel (powder boronizing)

Introduction

Metallographic analysis of 45# steel (powder carburizing) are provided in this paper to obtain information on microstructural details. This experiment includes sample preparation, optical metallography, and microstructure analysis.

Materials and Method

For this experiment, 45# steel powder that has been carburized was obtained.

Sample Preparation

The sample was cleaned then polished with an angel grinder to create a mirror finish on the sample.

Polishing with SiC

SiC was then used to polish the sample after the mirror finishing. A diamond paste was then used to promote finer polishing.

Polishing with Alumina

Alumina paste was then used to polishing the sample after the polishing with diamond paste.

Metal Etching

The sample was etched for five minutes with Nital etchant to reveal its microstructure.

Metallographic Analysis

An optical microscope was used in order to observe and take pictures of the etched sample.

Results and Discussion

The microstructure of the sample is shown in the figure 1. The microstructure consists mainly of martensite along with a small amount of ferrite. The martensite is characterized by its needle-like morphology and is formed by quenching and transformation (Q&T) of austenite. The small amount of ferrite observed is a result of the decomposition of martensite during the cooling process.

Figure 1. Microstructure of the 45# steel powder carburized sample.

Conclusion

Metallographic analysis of 45# steel powder carburized sample was carried out in this paper. Sample preparation, optical metallography, and microstructure analysis were performed. The microstructure of the sample was observed and consisted mainly of martensite and a small amount of ferrite. The results showed that the Q&T process during the carburizing process produced the needle-like morphology of martensite and the decomposition of martensite during cooling produced the small amount of ferrite.

45 steel is a low-alloy steel produced by quenching- tempering heat treatment. It belongs to high-strength steel and is widely used for manufacturing important mechanical parts.

45 steel mainly contains 0.42–0.50% carbon, 0.17–0.37% silicon, 0.50–0.80% manganese, 0.035% phosphorus, 0.035% sulfur, and 0.60–1.4% chromium. It has excellent comprehensive mechanical properties.

The microstructure of 45 steel is mainly composed of tempered sorbite(bainite) and a small amount of pearlite which are evenly distributed. Its longitudinal tensile strength and yield strength are very excellent, the impact toughness is also very good.

In addition, 45 steel can also be carburized, surface hardened and then quenched to obtain the corrosion resistance, wear and pressure resistance properties.

Based on the above information, it can be seen that 45 steel has excellent comprehensive mechanical properties, and is widely used in manufacturing important mechanical parts. The metallographic microstructure of 45 steel consists of two phases, tempered sorbite and a small amount of pearlite, which are evenly distributed.