Troubleshooting of the "seizing" fault between the pump plunger and the cylinder block of an excavator

After major overhauls and replacements of the cylinder block and plunger of the hydraulic pump of a HE-280 excavator, the hydraulic pump stopped working and was accompanied by abnormal noises. Disassembly and inspection revealed that the plunger was stuck to the cylinder block, presenting a "seizing" state. After conducting metallographic structure analysis on the cylinder block and plunger, it was confirmed that the residual austenite transformed into martensite, and the lower the temperature, the greater the transformation amount. In cold seasons, the residual transformation is completed in a very short time, causing the plunger to "seize up" due to its sudden increase in volume. For this purpose, the fit clearance between the cylinder body and the plunger of the hydraulic pump at room temperature can be measured with a special measuring tool. The cylinder block and the plunger are respectively subjected to cold treatment, that is, placed in a place of -50 to -60℃ for 30 minutes and then taken out. The fit dimensions when grinding the plunger to room temperature with a grinding machine; Perform laser quenching on the surface of the plunger; The surface of the plunger was polished again with metal-specific polishing paste, and the fault was eliminated after reassembly.