Metallographic diagram of 38CrMoAl (gas nitriding at 540°C after modulation)

The metallography of 38CrMoAL (after tempering the gas nitrided at 540°C )

Metallography is a method of examining the microstructure of metals through microscope observation. Metallography of 38CrMoAL (after tempering the gas nitrided at 540°C) is a part of the process of studying and understanding the effects of different heat treatments on the microstructure and properties of the material. The microstructure of the 38CrMoAL material is studied using a cross-sectional metallurgical microscope to observe the detailed structure of the material after heat treatment.

The 38CrMoAL (after tempering the gas nitrided at 540°C) is a low alloy steel with a nominal composition of 0.37% C, 0.25-0.45% Si, 0.8-1.25% Mn, 1.75-2.35% Cr, 0.30-0.45% Mo and 0.15-0.25% Al. The 38CrMoAL material is often treated with nitriding to increase its surface hardness and wear resistance as well as improving its fatigue and corrosion resistance. The microstructure of the 38CrMoAL material after nitriding consists of surface layers of hardened gamma ferrite and layers of diffusion of nitrogen atoms into the steels matrix.

When the metallography of the 38CrMoAL material is observed, the microstructure is made up of a surface layer of double-phase mixture of gamma ferrite (grain comprising of ferrite and carbide) formed on the steels matrix. The gamma ferrite grain are small in size and dark in colour. The nitrogen atoms are highly dispersed in the gamma ferrite grains, and give the microstructure a homogeneous and uniform appearance, with a uniform texture and texture.

The microstructure of the 38CrMoAL material also contains a layer of deep nitrided steel on the surface which increases the surface hardness, wear resistance and fatigue strength of the material. This layer is composed of a uniform distribution of nitrogen atoms embedded in the surface of the steel. The compound of nitrogen atoms in the alloyed steel creates a stronger hardening effect than a simple diffusion of nitrogen atoms.

The effects of the nitriding process on the microstructure of the 38CrMoAL material are very notable. The surface layer of the material is hardened more and has a more refined structure which gives the material improved wear resistance and fatigue strength. The uniformity of the grain structure in the microstructure is improved, allowing the material to have increased strength and increased wear resistance. The formation of the gamma ferrite grains in the 38CrMoAL material also brings about an improvement in the fatigue strength of the material.

The nitriding process also provides a greater degree of corrosion resistance for the 38CrMoAL material due to the protective layer of nitride on the surface. The protective layer of nitride on the surface of the material helps to impede the corrosion process, prevent rust from forming and can even help to reduce the effect of corrosion on the material.

Metallography of the 38CrMoAL (after tempering the gas nitrided at540°C) is an important process in the study and understanding of the effects of different heat treatments on the microstructure and properties of the material. The nitriding process increases the surface hardness, wear resistance and fatigue strength of the material while also improving the corrosion resistance. All of these characteristics contribute to the overall performance of 38CrMoAL in various application areas.

This is an image of an electron microscope of a sample of 38CrMoAl, that has undergone gas carburizing at 540°C. The matrix phase is a pearlite structure, which is composed of ferrite and cementite. There are some darkly-coloured islands with a faint cobidge structure, which is the 41CrNiMoV alloy steel precipitated during nitrogen segregation. It has a low melting point and exhibits greater thermal compatibility than other alloy steels.

The 42CrMo section was subjected to tempered Martensite, and the sample contains ferrite, tempered Martensite, and perlite regions. The 42CrMo section was further processed by tempering at about 250°C for half an hour, resulting in grain refinement and improved toughness. The hardness at the 42CrMo section was 500HV and the elongation was about 10%, which indicates that the processing was successful.

The image also shows that 38CrMoAl section has some distributions of darker colour iron carbides. These iron carbides are formed due to the precipitation of iron carbide during the process. This can reduce the elasticity and toughness by forming the carbides that reduce the movement of the gas molecules, which caused brittleness in the sample. This is due to the diffusion of nitrogen through the sample during the process, resulting in the precipitation of 41CrNiMoV which resulted in higher nitrogen content in the microstructure.

Since the sample underwent gas carburization and nitrogen segregation, it is expected to have higher resistance to wear and tear as compared to other lower alloy steels. The sample has good oxidation resistance owing to its high temperature compressive strength, and excellent corrosion resistance due to the high nitrogen content in its microstructure. Therefore, it is suitable for use in a wide range of application such as making spur gears and cutting tools.