The peeling defect of the injector ejector pin can be easily solved by the medium frequency induction heating machine

After the injector ejector rod of the diesel unit of power generation equipment had been running for 5000 hours, its working surface suffered from pitting and peeling and early failure, causing a production accident.

The fuel injector ejector material is 90MnCrV8 (German brand). By observing the microscopic morphology of the ejector working surface under the scanning electron microscope, we can see the pitting and peeling of different depths, concentration and dispersion.

The metallographic structure of the fuel injector ejector is tempered martensite + uneven fine network carbides, which are generally distributed in a band shape. The structure reduces the grain boundary strength of the material and increases the brittleness. This shows that the material’s thermal processing and heat treatment processes are improper. After observing the crack expansion at the bottom of the pockmark, it can be seen that under the action of fatigue stress on the fuel injector ejector rod, the crack nucleated at the bottom of the pockmark and developed in a direction of 45° with the surface, and then in a direction parallel to the surface. develops, and then extends to the surface of the workpiece in a direction of 45° to the surface until the surface area is peeled off.

Measures to prevent and control injector ejector pin spalling and failure are as follows:

(1) Strictly control the uneven metallurgical structure of the material and the segregation of carbide grain boundaries to prevent and reduce the embrittlement and weakening areas formed by the segregation of carbides or impurities in the grain boundary area of the material, leading to cracks and spalling.

(2) Improve the heat treatment process, use a medium-frequency induction heating machine for heat treatment, and eliminate carbide nets to reduce material brittleness, improve material strength and toughness, prevent the occurrence and expansion of micro-cracks, and prevent early failure from pitting and spalling on the surface of parts.

After heat treatment with a medium frequency induction heating machine, the peeling defects on the surface of the injector ejector disappeared, and the service life and pressure resistance were greatly improved, meeting the needs of the work.