H13钢表面激光熔覆改性研究

【作者】 刘录录；

【导师】 孙荣禄；

【作者基本信息】 天津工业大学 ， 机械制造及其自动化， 2008， 硕士

【摘要】 为了提高H13钢表面的耐磨性能,本文进行了NiCrBSi、NiCrBSi+Ti、NiCrBSi+Ti+C、NiCrBSi+TiC等多种材料的激光熔覆试验。通过对不同材料熔覆层的宏观质量的对比分析,优选了熔覆材料并优化了激光熔覆工艺参数;利用XRD、SEM等手段对熔覆层的微观组织进行了表征;利用HXD-1000型显微硬度计测试了熔覆层的显微硬度;利用M-200型磨损试验机测试了熔覆层的摩擦磨损性能。试验结果表明,熔覆材料与激光熔覆工艺参数是影响激光熔覆层宏观质量的主要因素,在优化工艺参数下,可以获得外观光滑,均匀连续的NiCrBSi和NiCrBSi+Ti+C激光熔覆层。微观组织分析表明,激光熔覆层存在三个不同的区域,由表及里依次是熔覆层,熔覆层与基底的结合区及基底热影响区。NiCrBSi熔覆层由γ-Ni,Cr₇C₃,CrB等物相组成;NiCrBSi+Ti熔覆层由γ-Ni、Cr、Ni与Ti金属间化合物等相组成;NiCrBSi+Ti+C熔覆层由γ-Ni,Cr₇C₃、原位合成的TiC等相组成;NiCrBSi+TiC熔覆层由γ-Ni、Cr₇C₃、未溶TiC和溶解并重新析出的TiC等相组成。激光熔覆层的硬度由熔覆层到热影响区不断下降。NiCrBSi+Ti+C合金熔覆层的最高硬度值为HV850,比H13钢提高了约3倍,NiCrBSi熔覆层的最大硬度为HV700,比H13钢提高了约2倍。摩擦磨损试验结果表明,NiCrBSi激光熔覆层的磨损体积约为H13钢合金的1/10,NiCrBSi+Ti+C激光熔覆层的磨损体积约为H3钢合金的1/15,在磨损条件越苛刻的情况下NiCrBSi+Ti+C激光熔覆层的优良耐磨性能越突出。NiCrBSi激光熔覆层的磨损为氧化磨损和磨粒磨损。NiCrBSi+Ti+C激光熔覆层的磨损主要为熔覆层自身TiC颗粒剥落后而产生的磨粒磨损。NiCrBSi+Ti+C激光熔覆层的高硬度和高耐磨性能是由于涂层中存在颗粒强化、细晶强化和固溶强化等多种强化机制。更多还原

【Abstract】 In order to improve the wear resistance of H13 steel,the laser claddings of H13 steel substrate with NiCrBSi,NiCrBSi+Ti,NiCrBSi+Ti+C and NiCrBSi+TiC were performed.The macroscopic qualities of all kinds of the coatings were analysed and compared,and the process parameters of laser cladding and the materials of coatings were optimized.The microstructure of the laser coatings was characterized by XRD and SEM.The microhardness of the coatings was examined and contrasted using HXD-1000 microhardness tester.The wear properties were examined using M-200 wear test machine.The results show that the clad materials and the process parameters are the important factors to influent the quality of laser cladding.In the condition of optimized process parameters,we can obtain the smooth and continuous laser claddings of NiCrBSi and NiCrBSi+Ti+C.The miscrostructure analyses show that three regions with different microstructures exist in the surface of coatings:the clad layer,the binding zone of the clad layer with the substrate,and the heat-affected zone in the substrate.The clad layer of NiCrBSi coatings on H13 alloy substrate consists of the phases ofγ-Ni,Cr₇C₃ and CrB.The clad layer of NiCrBSi+Ti coatings on H13 alloy substrate consists of the phases ofγ-Ni,compound of Cr and Ni with Ti.The clad layer of NiCrBSi+Ti+C coatings on H13 alloy substrate consists of the phases ofγ-Ni,Cr₇C₃ and the in-situ synthesized TiC.The clad layer of NiCrBSi+TiC coatings on H13 alloy substrate consists of the phases ofγ-Ni,Cr₇C₃ and the undissolved TiC and the precipitated TiC distributed dispersively.The hardness profiles of all the coatings obey the same law.The hardness is decresed from the clad layer to the heat-affected zone.The hardness of the clad layer of NiCrBSi+Ti+C coatings reaches HV850,which is improved by near three times compared with the substrate H13 steel.The hardness of the clad layer of NiCrBSi coatings reaches HV700,which is improved by above twice compared with the substrate H13 steel.The tribological properties on M-200 wear test machine show that the wear volume of the NiCrBSi coating is 1/10 of the H13 steel,the wear volume of the NiCrBSi+Ti+C coating is 1/15 of the H13 steel.The wear resistance of the NiCrBSi+Ti+C coating is better in the strict conditions.The wear mechanism of the NiCrBSi clad layer is a mixture of oxidation wear and grain abrasion.The wear of NiCrBSi+Ti+C clad layer is the abrasion,which is caused by the peeling-off TiC particles from the clad layer.The NiCrBSi+Ti+C clad layer which obtains the good wear resistance and microhardness could be strengthened by several mechanisms, including the hard particle strengthening,fine-grain strengthening and solid solution strengthening.更多还原