Metallographic diagram of W6Mo5Cr4V2 (heating, quenching and oil cooling at 1220°C)

At a magnification of 500X, the microstructure of CrW6Mo5V2 steel heated to 1220℃ followed by oil quenching can be observed through a Scanning Electron Microscope (SEM). The polished cross sections were used to view the microstructure by SEM. Dislocations, grain boundaries, and pro-eutectoid ferrite can be evidenced.

Under SEM, the microstructure of CrW6Mo5V2 steel consists mainly of a matrix of pearlite, which is a lamellar eutectoid composed of pro-eutectoid ferrite and cementite. The pro-eutectoid ferrite appears to be a greyish-white lamellar structure that is temper-resistant, and the cementite appears to be black striations in between the light ferrite layers. Both the ferrite and cementite are the two major constituents of pearlite. Further analysis of the microstructure shows thin bands of martensite located along the pearlite grain boundaries, and further evidence suggests that they were produced due to insufficient diffusion during the rapid cooling process.

Dislocations are also observed in the material. The dislocations appear as imperfections and are generally characterized as line-like defects that result from plastic deformation. This indicates that permanent strains have been created due to plastic deformation, and the metal structure has lost its elasticity. Additionally, there are also small coarse carbides present in the structure which appear both as checkerboard pattern-like clusters, as well as along the grain boundaries.

The grain boundaries of the steel can be easily differentiated from the matrix, and the boundaries appear as darker, thin lines that have the same orientation of the crystallographic axes. Electron diffraction analysis of the grain boundaries reveals them to be mainly low-angle and fine boundaries with Burgers vectors of <111> type.

The overall microstructure of the material gives it high resistance to creep, which is a detrimental process caused by plastic deformation. The regular pattern of mating grain boundaries gives the material an efficient path with respect to the flow of dislocations, and prolonged exposure to loads (such as temperature) gives the material a good combination of stability and strength.

In conclusion, the microstructure of CrW6Mo5V2 steel heated to 1220℃ and oil quenched can be observed at 500x magnification through SEM. The primary structure is composed of a matrix of pearlite, which is formed by pro-eutectoid ferrite and cementite. Dislocations and small coarse carbides are also present. Grain boundaries are observed as thin dark lines, which are mostly low-angle and fine due to their Burgers vectors of <111> type. This microstructure gives the material high resistance to creep and a good combination of stability and strength.

60Cr6W6Mo5Cr4V2 is a high-temperature and corrosion-resistant steel alloy for use in elevated temperature service above 1200°F (649°C). Standard product forms are round and rectangle bars with cross-sections of 0.47 inch (12 mm) and 0.80 inch (20 mm) through 6.0 inch (152 mm) diameter.

60Cr6W6Mo5Cr4V2 steel is an air-hardened steel alloy with excellent strength and oxidation resistance, particularly at elevated temperatures to 1220°C. This steel alloy provides superior performance in applications that require high-temperature resistant alloys where oxidation and sulfidation resistance are required. These are often found in aerospace applications, power generation and other specialized mechanical components.

When it comes to heat treatment, the alloy is suitable for a wide range of heating and cooling applications. Due to its high strength, and excellent hardness and wear resistance, it is typically hardened through a austenitizing/quenching process, typically at 1220°C, followed by gradual cooling and tempering.

To analyze the metallographic structure of the steel alloy, the following are typically run: optical metallography, hardness measurement and corrosion test. The metallographic microstructure of the steel alloy will be composed of fine and large, even bands of ferrite and pearlite. Characteristic grains of martensite, rounded to elongated, are often scattered throughout the sample and trace amounts of sigma phase may be present. The hardness, of the alloy should be between 370 and 400RMN.

Finally, in terms of corrosion resistance, this steel alloy is highly resistant to blisters, pits, and general corrosion after exposing to acid and other corrosive materials. When appropriate surface treatments are applied, such as a thin transparent barrier coating or painting, the alloy can be made even more resistant to corrosion.