38CrMoAl (vacuum nitriding) metallographic diagram

The metallography of 38CrMoAl (vacuum nitrided) involves the study of the microstructure and properties of the material. In particular, the analysis involves the identification and evaluation of the various alloying elements, grain fineness and micro-defects in the microstructure. The aim of this analysis is to determine the material suitability for its proposed applications.

At the macroscopic level, 38CrMoAl (vacuum nitrided) has a homogenous distribution of elements and a uniform grain size. The microstructure of this alloy consists of a mixture of ferrite and pearlite which are further divided in lathy, granular and bainitic structures. Micro-defects, such as inclusions, porosity, segregation and cracking may also exist, though they are typically small and localized.

At the microscopic level, the mixed structure of 38CrMoAl (vacuum nitrided) is readily observed through optical microscopy and scanning electron microscopy (SEM). Metallographic images show a significant amount of carbides in the material microstructure, together with martensite. The carbides are generally needle-like in shape and often present in high-density orientations. Additionally, the presence of graphite flakes and the occurrence of an increase of alloying elements has been recorded.

The grain size of 38CrMoAl (vacuum nitrided) is through the range 10–20μm. Micro-defects, however, may be observed upon using high-resolution SEM. Typical defects such as cracks, inclusions, segregation and porosity are seen about the grain boundaries.

The hardness of 38CrMoAl (vacuum nitrided) is mainly determined by the concentration of carbides in the microstructure. Generally, higher carbides concentration yields higher hardness values. The Vickers Hardness of 38CrMoAl (vacuum nitrided) is typically about 900 HVN and could be increased up to 1100 HVN depending on the level of nitriding.

The analysis of the 38CrMoAl (vacuum nitrided) metallography structure has been validated through several tests. Generally, the obtained results are consistent with the assumed characteristics of the alloy. In particular, the analysis revealed a homogeneous microstructure with no significant micro-defects, acceptable grain size and high hardness. This suggests the material is suitable for its proposed applications.

38CrMoAl steel is a high-strength alloy tool steel. It is usually treated with vacuum nitrogen diffusion. The purpose is to reduce the oxygen content and obtain good comprehensive mechanical properties.

The 38CrMoAl steel has a certain tempering softening effect during tempering, which can obtain an adequate plasticity. In a certain range of tempering temperature, the so-called tempering effect can be obtained, that is, the metallographic structure of the steel can be transformed and softened, so as to achieve good comprehensive mechanical properties.

The microstructure of 38CrMoAl steel after vacuum nitrogen diffusion treatment is observed by metallographic microscope. The ferrite and pearlite matrix are clearly distinguishable. There are some a small amount of complex shape carbides distributed in the microstructure. The content of large carbides is basically zero, which indicates that the pearlite structure is basically uniform. And this small amount of carbide provides the microstructure with sufficient hardness, wear resistance and other properties.

The carbide precipitation of 38CrMoAl steel after vacuum nitrogen diffusion treatment is mostly needle-like and lath-shaped, and is dispersedly distributed. The actual size is about 0.8-1um, and the shape is close to the original state. There are numerous small and fine dispersed lath-shaped carbides in the matrix. This distribution and shape of carbide provide the material with sufficient wear resistance and other properties.

In summary, the metallographic structure of 38CrMoAl steel after vacuum nitrogen diffusion treatment is a ferrite and pearlite matrix with a small amount of fine dispersed lath-shaped carbides. This structure can provide the material with sufficient hardness, wear resistance and other properties.