Abstract: Medium-blocking-type sensor can semi-quantitatively evaluate the solid particle contamination level in oil, and the key element of this sensor is the metal micro-pore filter membrane. A new method was proposed to make the metal micro-pore filter membrane in high price/performance ratio by using electro-less nickel-plating on a kind of 600-mesh twill weave stainless steel wire meshes. The technological process of electro-less nickel-plating is well studied and summarized. Furthermore, the composition of the coating, the combination of the coating and the base material and the sizes of micro-pores and wire diameters of the micro-pore filter membrane are analyzed by scanning electron microscope (LEO 1450 VP) and spectrum analyzer (INCA ENERGY 300). The results show that the layer of the micro-pore filter membrane got by studied technological process is low-phosphorus coating with tensile strength of 400-700 MPa and hardness of 580 HV, showing the coating and the base material are combined firmly. The micro-pore filter membrane with sizes of 14 m and 10 m can be got after 20 minutes’ and 30 minutes’ nickel-plating, respectively. The thickness of the wire diameter increased uniformly, and the micro pores are almost in the same size. In order to check the quality of the micro-pore filter membrane, the repeatability accuracy and the precision in contamination level testing of a medium-blocking-type sensor made with the studied metal micro-pore filter membrane are carried out, and the results show that the medium-blocking-type sensor has good repeatability and its contamination level testing results consistent with the actual value. Therefore, the micro-pore filter membrane made through this method can meet the requirements of medium-blocking-type sensor.

Key words: medium-blocking-type sensor;metal micro-pore filter membrane;electro-less nickel-plating;contamination level testing