Failure Analysis of Tokimec Vane Pump Wear

Domestic pump commonly used in the process of using the short life of the problem, wear is one of the most common defects. To fundamentally improve the reliability of the pump, it should be from the system engineering point of view, taking into account the use of the pump, materials, design, manufacturing processes and other factors to be studied. At present, the vane pump commonly used materials are high lead system, anchorage aluminum system, less variety of materials. This example of a company vane pump 38CrMoA1A and W6Mo5Cr4V2 wear failure analysis. (1) Experiment and Analysis ① Visual Inspection Materials: The vane pump stator material is 38CrMoA1A, and the vane material is W6Mo5Cr4 V2 0 The two groups of vane pumps for inspection have been seriously worn. Among them, the main wear failure mode of the inner working surface of the stator of the 1-vane pump is sticking and wear. The main wear failure modes of the inner working surface of the inner stator of 2-vane pump are oil mist with small vibration Sliding wear. ② Metallographic failure analysis of parts with wire cutting method intercept the sample, and ground into a metallographic sample. Observed with a light microscope, magnification of 10 times and 440 times. Microscopic observation of the metallographic sample before etching shows that there are few defects such as microscopic inclusions and micro-holes in the two kinds of materials, and the structure is relatively dense and uniform, and the material quality is normal. After etching with 4% nitric acid alcohol, the microstructure was observed. The microstructure of # 1 and # 2 leaves mainly consisted of martensite and fine grained carbides. 1 # Compared with 2 # leaves, there is a small amount of massive carbides, carbide particles larger than the size of 5 to 10 times. 1 # and 2 # stator matrix and the surface layer of the microstructure is different from the main body by the organization of directional tempering sorbite. The microscopic observation of the nitrided layer on the stator surface shows that there is a discontinuity on the outer surface of the nitrided layer of the stator 1 #, and the extremely thin compound is from the bright layer. Since the thickest of the bright layer is about 1 μm, the nitride layer is mainly composed of the diffusion layer The thickness of the diffusion layer is 13 to 16 μm, the brittleness level of the nitride layer is 1 level, and the shape of the nitride layer is 1 level; there is a continuous bright white layer of compound on the outer surface of the 2 # stator nitride layer with a thickness of about 2.5 μm, The surface of the diffusion layer, the thickness of 15 ~ 17μm, nitride layer brittleness level of 1, the nitride morphology of the first level. (3) Hardness analysis Rockwell hardness and microhardness were measured respectively on the matrix of each sample. The load of microhardness was 200 g and the holding time was 308, and the measurement results are shown in Table 1-1. Table 1-1 Matrix hardness measurement results (2) Analysis and discussion From the blade pump hardness analysis results, 1 # blade material hardness average of 62.4HRC, and the stator frictional hardness difference of 28.4HRC; 2 # blade material Hardness average of 66.2HRC, and the friction between the stator composition of the hardness difference of 33.9HRC; 2 # vane pump blade hardness is higher, is conducive to improving the wear resistance of the blade. From the metallographic analysis results, 1 # stator nitride layer is mainly composed of diffusion layer, the outer surface of white bright compound layer does not exist continuously, and extremely thin, 2 # stator nitride layer in addition to the diffusion layer, the outer surface there is continuous white The compound layer, which is thicker than the 1 # stator compound layer, has a higher hardness and should exhibit higher wear resistance than the 1 # stator. However, from the two failed vane pump stators, the wear depth of the inner working surface has been Exceeds the thickness of the nitride layer, so the two vane pump structure size and working environment medium material wear and tear failure form has a significant impact. According to the microstructure and hardness analysis results, from the material point of view, the appropriate increase in blade hardness and depth of nitrided layer is conducive to improving the wear resistance and life of the vane pump.

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