Reciprocating electrolyte jet with prefabricated-mask machining micro-dimple arrays on cast iron cylinder liner

Abstract

Cast iron cylinder liner in the diesel engine is putting forward higher requirements on the tribological performance. The micro-texture machined on the cast iron cylinder liner surface has demonstrated the brilliant potential of friction reduction. However, the existing micro-texturing technologies of the cylinder liner have some limitations, such as the workpiece deformation, the low processing efficiency and the high cost of the machining equipment. In the paper, the reciprocating electrolyte jet with prefabricated-mask (REJP) machining technology was used to generate circular dimple arrays on the cast iron cylinder liner. The micro-machining equipment adopts the direct current power instead of the pulse power. The electrolyte jet as the cathode driven by the step-wise motor realizes the reciprocating movement. In addition, the arc shape of the cathode opening is identical with the cylinder liner to guarantee the same inter-electrode gap along the curved liner. After the electrolyte flows out of the cathode opening, three machining areas including the injected area by the vertical flow, the activated area and the wetted area by the horizontal flow, are formed on the cylinder liner surface by the prefabricated-mask. The circular dimple can be uniformly fabricated in arrays with the following optimized machining parameters: cathode velocity = 10 mm/s, electrolyte flow = 45 ml/s, applied voltage = 10 V, electrolysis time = 60 s. By using the prefabricated-mask with the array hole of 800 μm in diameter, the best dimension of micro-dimple is about 43 μm in depth and 822 μm in diameter. Compared with the non-dimpled cylinder liner, the friction coefficient of the micro-dimpled cylinder liner decreases as much as 12.0% under the heavy load of 20 MPa.