M6C carbides in Fe-Mo-C alloy


Figure 1: Scanning electron micrograph of an Fe-Mo-C alloy with M6C carbides in the course of dissolution. Courtesy INPG, Grenoble. Scale bar: 10 µm.

Carbide name: M6C
Record No.: 1183
Carbide formula: M6C
Carbide type: M6C
Carbide composition in weight %: No data
Image type: SEM
Steel name: Fe-Mo-C alloy
Mat.No. (Wr.Nr.) designation: No data
DIN designation: No data
AISI/SAE/ASTM designation: No data
Other designation: No data
Steel group: Steels
Steel composition in weight %: No data
Heat treatment/condition: No data
Note: Disappearance of non-equilibrium carbides in a pseudo-peritectic reaction: The above examples have shown that carbides formed during solidification remain present, in spite of the pseudo-peritectic reaction that ought to have caused them to disappear, at least partially. In multi-component alloys, according to the phase rule, it is quite normal for numerous phases to co-exist. However, the persistence of phases that are no longer in equilibrium is due to kinetic factors that make many reactions very sluggish. When carbides redissolve, the process is not the reverse of that involved in their growth, that is, gradual thinning. When epitaxial relationships exist between carbides {e.g. M7C3 and M3C, M7C3 and M23C6), the peritectic carbide nucleates on the phase that has become metastable and grows at its expense. Alloying elements are transferred from one carbide to the other. Some carbides, such as M^C, dissolve in another manner, disintegrating and becoming porous. Inside carbide particles, in regions where the carbon has left, transient phases may form, such as ferrite. Figure 1 shows the resulting "moth-eaten" appearance of M6C carbides in the course of dissolution in an Fe-Mo-C alloy.
Links: No data
Reference: Not shown in this demo version.

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