This paper discusses the main reasons for the leakage of hydraulic cylinder, analyzes the advantages and disadvantages of polyurethane seal rings for hydraulic cylinder reciprocating sealing, compares the performance and characteristics of several commonly-used reciprocating seals, and studies the sealing mechanism, material characteristics , effects of practical applications and gives the solution of Packing PTFE combined sealing.

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To obtain high properties of laser cladding layer, and to expand the service life of the mold, the laser cladding layer with Ni-WC and SiC on the surface of H13 steel made by using a laser. Then the cross-section and surface morphologies of the coatings and wear tracks were observed with a JSM-5610 type scanning microscope. The friction and properties were examined under dry sliding conditions using a WTM-1E type ball-on-disc machine. The wear mechanisms are discussed as well. The results show that the composite coating is very compact and good blinding with the substrate after laser remelting, and the wear mass loss of the composite coating reduced to about 1/4 of the matrix material.