| In the industry and transportation, wear resistance of rail is poor at winding road, surface of roll needs strengthening and repairing, wear resistance and corrosion resistance of twin screw extruder needs improving. Surface strengthen technology can effectively change surface performance of materials and make their service life longer. In this paper, in order to reduce cost and increase economy benefit, electrical discharge surface strengthening technology was adapting to strengthen these three kinds of materials.U70MnSi, 42CrMo, and 40Cr were surface strengthened by adopting different positive electrodes and technological parameters on a self-made electrical discharge surface strengthening equipment. Micro-structure and wear morphology of strengthen layer were study by using optical microscope and glow discharge instrument. Structure and composition distribution of strengthen layer were analysis by adopting X-ray diffraction glow discharge instrument. Hardness and its distribution along strengthen layer were measured on micro-hardness machine. Wear resistance of strengthen layer was evaluated on MM-200 wear experiment machine. On the basis of above experiments, effect factors on the quality, micro-hardness, wear resistance and corrosion resistance of discharge surface strengthening layer are researched as well as the wear and corrosion mechanisms of strengthened layer were studied, and wear and corrosion resistance of specimen under stimulated operating mode were obtained. Main results were achieved as follows:Strengthen layers that were gained in this study are alloyed coatings consisting of fain crystalline structure and non-crystalline, and contain carbides.nitrides, oxide and elements of positive electrodes and specimens. Positive electrodes and specimens elements distribute in gradient along strengthening layer depth direction, melting and permeating and diffusion between elements occurs. Strengthen layer is consist of white-bright area, gradient area and thermal influence area. There are not only micro-hole, crackle and survive tension on the surface of strengthen layer but also micro-hole in it.The micro-hardness of strengthen layer is the highest in the white-bright area (U70MnSi, 42CrM and 40Cr strengthened can reach respectively above HV1450, HV1650 and HV1530), the hardness of strengthen layer decreases in gradient along depth direction.When the hardness of upper sample is not varying, wear resistance of lower samples is rising and upper sample is decreasing with the rising of surface hardness of lower sample under rolling wear. In wear system of this paper, when both lower and upper samples are either strengthened or non-strengthened sample, fairly good wear resistance match can be obtained.When lower and upper samples are either strengthened, non-strengthened or different materials, the wear mechanisms primary are adhesive wear, abrasive wear and fatigue wear, the proportion of them depends on the surface performance of mates under rolling-wear; however, besides adhesive wear, fatigue wear, abrasive wear and there is also oxidation wear under rolling-sliding wear.Micro-hole, crackle, surface surviving tension and impurity in strengthened layer will quicken corrosion of layer and make its corrosion decrease; but tight fine crystalline structure and non-crystalline structure can improve corrosion of strengthened layer. Comparing the two effective factors, the influence of last one is beyond that of first, for example, corrosion of 40Cr steel strengthened by FW—1101 electrode increases.Wear resistance and corrosion resistance of 40Cr, 42CrMo and U70MnSi strengthened are improved in different ways under corresponding operating mode. Wear resistance of them are raised about 4, 4.5 and 3-4 times, respectively. Corrosion of 40Cr strengthened is improved 2.2 times in 10%IICI solution, and 4.5 times in 10%NaOH. Adapting electrical discharge surface strengthen can remarkably lengthen life of these three kinds' materials.
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