H13钢激光表面强化与熔覆涂层的组织及磨损性能研究

发布时间：2019-05-30 04:11

【摘要】：H13(4Cr5MoSi V1)钢具有较好的综合性能,适用于制造精锻模、热挤压模、芯棒以及压铸模。多数模具的失效首先是从表面开始的,因而,采取恰当的方式改善表面组织、提高表面性能,可以有效的提高模具的使用寿命。本文采用5 kW连续CO2激光器在H13模具钢表面制备激光熔凝强化层和激光熔覆Co基、Ni基复合涂层。分别在H13钢表面熔覆Stellite-6、St6+5%WC、St6+5%WC+1%RE、St6+2.5%WC+1%RE、St6+7.5%WC+1%RE、St6+10%WC+1%RE钴基合金,制得显微组织均匀细小的钴基复合熔覆层。激光熔覆的镍基复合熔覆层包括Ni45、Ni45+5%WC、Ni45+5%WC+1%RE和Ni60AA、Ni60AA+5%WC、Ni60AA+5%WC+1%RE。采用光学显微镜、扫描电子显微镜、X射线衍射仪及透射电子显微镜对熔凝硬化层和熔覆层的显微组织、元素分布及相组成进行了系统研究;采用显微硬度计、磨损试验机研究了熔覆层的显微硬度和磨损性能。结果表明:(1)H13钢激光熔凝后的组织,由表层至次表层依次是垂直于激光扫描方向的树枝晶、胞状晶和马氏体组织及高温回火区,高温回火区的马氏体组织粗大,且残余奥氏体的含量减少。激光熔凝后,除原始组织中的相,没有新相生成。激光熔凝后的显微硬化层深度约1.1mm,最高硬度746HV0.2。硬化层的耐磨性相对调质处理后的H13钢的耐磨性有较大程度的提高。(2)钴基激光熔覆层与基体为冶金结合,各熔覆层的基体相组织为γ-Co,增强相组织均包括(Mn,Cr)7C3、Cr23C6、Co CX等相,加入WC后,熔覆层的增强相中增加了Co6W6C、WC、WC1-X相;稀土元素的加入有效控制了裂纹的生成,宏观形貌良好。熔覆层显微硬度为560 HV0.2~710 HV0.2;摩擦磨损试验表明,在相同条件下,耐磨性能由高到低依次是St6+7.5%WC+1%RE、St6+5%WC+1%RE、St6+2.5%WC+1%RE、St6、St6+10%WC+1%RE、H13钢。(3)Ni45基熔覆层的主要相组成为均匀细小的γ-Ni与枝晶间的Fe Ni3、C6(Cr,Co,Ni)23、Mn23C6等相组成的共晶组织。Ni45基熔覆层的显微硬度为525HV0.2~550HV0.2,熔覆层的耐磨性相对H13钢基体有较大程度的提高,尤其是在高载荷下熔覆层的磨损机制主要是磨粒磨损和剥层磨损,并未出现严重磨损。加入WC后耐磨性的提高尤为明显。(4)Ni60AA基熔覆层的微观组织为γ-Ni固溶体基体上均匀分布着超细网状共晶组织。熔覆层有较强的裂纹敏感性,加入稀土元素后裂纹、气孔等缺陷有一定程度减少。Ni60AA基熔覆层的硬度和耐磨性较基体都有很大程度提高。Ni60AA熔覆层的显微硬度为750HV0.2~800HV0.2,约为H13钢基体的1.78倍,Ni60+5%WC、Ni60+5%WC+1%RE熔覆层的显微硬度为800HV0.2~900HV0.2,约为基体硬度的两倍。
[Abstract]:H13 (4Cr5MoSi V1) steel has good comprehensive properties and is suitable for manufacturing precision forging die, hot extrusion die, mandrel and die casting die. The failure of most dies begins from the surface first. Therefore, the service life of the die can be effectively improved by adopting appropriate ways to improve the surface structure and surface properties. In this paper, laser melting strengthening layer and laser cladding Co based, Ni based composite coating were prepared on the surface of H13 die steel by 5 kW continuous CO2 laser. Stat-6, St6 5%WC 1% RE, St6 2.5%WC 1% RE, St6 7.5%WC 1% RE, St6 10%WC 1%RE cobalt base alloy were deposited on the surface of H13 steel, respectively, and the cobalt base composite coating with uniform microstructure was prepared by coating Stat-6, St6 and 1% RE, St6 7.5%WC 1% RE, St6 Co-base cobalt-based alloy with uniform microstructure and fine microstructure on the surface of H13 steel. The nickel-based composite coatings coated by laser include Ni45,Ni45 5% WC, Ni45 5%WC 1%RE and Ni60AA,Ni60AA 5% WCand Ni60AA 5%WC 1% re. The microstructure, element distribution and phase composition of melting hardening layer and coating layer were systematically studied by optical microscope, scanning electron microscope, X-ray diffractometer and transmission electron microscope. The microhardness and wear properties of the coating were studied by means of microhardness tester and wear tester. The results show that: (1) the microstructure of H13 steel after laser melting is dendritic, cellular and martensite structure perpendicular to the direction of laser scanning from the surface to the subsurface, and the martensite structure in the high temperature tempering zone is coarse. And the content of retained Austenite decreases. After laser melting, no new phase is formed except the phase in the original structure. The depth of microhardened layer after laser melting is about 1.1 mm, and the highest hardness is 746HV0.2. The wear resistance of hardened layer is much higher than that of H13 steel treated by quenching and tempering. (2) Cobalt based laser cladding layer is metallurgical bonded with matrix, and the matrix phase structure of each coating layer is gamma-Co, enhanced phase structure, including (Mn,). The wear resistance of hardened layer is greatly improved compared with that of H13 steel treated by quenching and tempering. (2) Cobalt based laser coating layer is metallurgical bonded to matrix. Cr) 7C3, Cr23C6, Co CX and so on. After adding WC, the Co6W6C,WC,WC1-X phase was added to the reinforced phase of the coating layer. The addition of rare earth elements effectively controls the formation of cracks, and the macroscopic morphology is good. The microhardness of the coating is 56 HV0.2~710 HV0.2;. The friction and wear tests show that under the same conditions, the wear resistance from high to low is St6 7.5%WC 1% RE, St6 5%WC 1% RE, St6 2.5%WC 1% RE, St6, St6 10%WC 1% RE. H13 steel. (3) the main phase composition of Ni45 based coating is uniform and fine Fe Ni3,C6 (Cr,Co,Ni) 23, Mn23C6 and so on. The microhardness of Ni45 based coating layer is 525HV0.2 and 550HV0.2. the microhardness of Ni45 based coating layer is 525HV0.2 and 550HV0.2, and the microhardness of Ni45 based coating layer is 525HV0.2 and 550HV0.2, the microhardness of Ni45 based coating layer is 525HV0.2 and 550HV0.2, The wear resistance of the coating layer is much higher than that of H13 steel matrix, especially under high load, the wear mechanism of the coating layer is mainly abrasive wear and peeling wear, and there is no serious wear. The wear resistance of Ni60AA based coating layer was improved especially after adding WC. (4) the microstructure of Ni60AA based coating layer was uniform distribution of ultra-fine reticulated eutectic structure on the matrix of 纬-Ni solid solution. The hardness and wear resistance of Ni60AA based coating are much higher than those of matrix. The microhardness of Ni60AA coating is 750HV0.2 and 800HV0.2, and the hardness and wear resistance of Ni60AA based coating are 750HV0.2 and 800HV0.2. the hardness and wear resistance of Ni60AA based coating are 750HV0.2 and 800HV0.2. the hardness and wear resistance of Ni60AA coating are 750HV0.2 and 800HV0.2, respectively. The microhardness of Ni60 5%WC 1%RE coating is about 1.78 times of that of H13 steel matrix, and the microhardness of Ni60 5%WC 1%RE coating is about 800HV0.2 and 900HV0.2, which is about twice the hardness of H13 steel matrix.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4

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