| HOU You-zhong,QI Xian-sheng,DENG Hong-jian,LI Shi-liang,NIU Fu-jie.Material Selection and Mechanical Property Evaluation for Additively Remanufactured EMU Axles[J],49(12):162-169, 219 |
| Material Selection and Mechanical Property Evaluation for Additively Remanufactured EMU Axles |
| Received:November 10, 2019 Revised:March 10, 2020 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2020.12.018 |
| KeyWord:remanufacturing, EMU, axle, laser cladding, NiCrMo alloy, press-fitting curve |
| Author | Institution |
| HOU You-zhong |
CRRC Qingdao Sifang Co., Ltd, Qingdao , China |
| QI Xian-sheng |
CRRC Qingdao Sifang Co., Ltd, Qingdao , China |
| DENG Hong-jian |
CRRC Qingdao Sifang Co., Ltd, Qingdao , China |
| LI Shi-liang |
Shaanxi Tyontech Intelligent Remanufacturing Co., Ltd, Xi’an , China |
| NIU Fu-jie |
CRRC Qingdao Sifang Co., Ltd, Qingdao , China |
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| Abstract: |
| The work aims to select the optimum material for remanufacturing of EMU axles and meet the mechanical property requirements of the axle and the conditions of the wheelset press-fitting. The appropriate material for the remanufacturing of the EMU axles was determined through selecting alloy materials of different chemical composition as well as comparing and analyzing mechanical properties, coefficient of linear expansion, composition in the dilution zone of fusion area, and hardness variation of the deposited metal by laser cladding technology. The cladded specimens were analyzed in terms of macroscopic structure, microstructure, chemical composition, hardness, mechanical properties and wheelset press test by optical microscopy, scanning electron microscopy and nano indentation. The microstructure of the laser cladding fusion area for Fe314 and Fe316 should consist of A+F as predicted by Schaeffler composition diagram, but the hardness value of the actual fusion area was higher than 600HV, which implied the existence of martensite formation. On the other hand, the hardness of the fusion zone was consistent with the deposited Fe310 and NiCrMo alloy. The mechanical properties of Fe310 were lower than those of EA4T steel, and the coefficient of linear expansion was much different from that of the EA4T steel. As such, Fe310, Fe314, and Fe316 were regarded not suitable for remanufacturing of EMU axles. NiCrMo was selected instead because the tensile strength was 790 MPa, the yield strength was 542 MPa, the impact toughness was 68 J/KU5 for the deposited NiCrMo alloy, and it had a similar coefficient of linear expansion compared with EA4T steel. In addition, the compressive elastic modulus Er in nano indentation was 180~185 GPa for the NiCrMo alloy, which was close to the compressive elastic modulus Er of 185~190 Gpa for the EA4T steel. The press-fit curve of remanufactured axles showed the maximum pressing force in the range of 680~1160 kN, which was deemed acceptable. NiCrMo alloy is selected as the laser cladding material for remanufacturing of EMU axle because its thermal expansion coefficient, mechanical properties and compressive elastic modulus of cladding metal and substrate EA4T steel are similar, and there is no brittle martensite structure in the transition zone of laser cladding metal, it has passed the press-fitting test of wheelset, and it meets the requirements of press-fitting curve of EMU. |
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