Erosion microscopic morphology and formation mechanism of hydraulic servo spool valve

Abstract

This study investigates the microscopic morphology of a hydraulic servo spool valve caused by particle erosion. The microscopic morphology of spool working edges and solid particle characteristics in oil of a typical hydraulic servo system were experimentally studied. The formation mechanism was analyzed using dynamic impact calculation. The results reveal that the erosion micro-morphology of the spool working edge was mainly characterized by surface peeling, notches, grooves, and chamfers. The contour of the working edge was rounded. The average and variance of the radius of the old spool’s working edges were obviously higher than those of the new spool. The main distribution range of solid particle size in typical servo-hydraulic system oil was 5–50 μm, and the number of particles decreased sharply with an increase in particle size, up to 90.89%. The actual shape of particles was close to an ellipsoid with strong erosion destructive power. When a single solid particle collided with the working edge, a large amount of stress was generated at the collision center point, and the stress can reach 1500 MPa when the pressure differential at the valve orifice was 3.5 MPa. The working edges were subjected to cyclic stress of high-frequency particle pulses, resulting in fatigue erosion.