H13钢激光熔覆工艺参数优化研究

发布时间：2018-06-29 10:28

本文选题：激光熔覆 + H13钢　；参考：《江苏理工学院》2017年硕士论文

【摘要】：H13(4Cr5MoSiV1)合金模具钢作为热作模具钢中使用非常广泛的模具钢之一,被广泛使用在冲击载荷大的压铸模、锻模、热挤压模等。在实际使用的过程中,例如,H13钢制分流模在铝型材的挤压过程中起到至关重要作用,其主要失效形式是热疲劳磨损和断裂。激光熔覆是一种先进的表面强化技术,可以很好地解决分流模的使用寿命问题。从现有的研究报道来看,在H13钢表面熔覆高温合金增强相的涂层,特别是有关如何获得使熔覆涂层质量良好的激光熔覆工艺参数的研究目前偏少。本文采用激光熔覆技术在H13钢表面激光熔覆Ni基合金涂层,分析了涂层与基体结合的组织形貌、物相组成以及涂层的力学性能。并依据涂层的熔覆尺寸,采用数据分析PCA-TOPSIS法,优化得出最优的工艺参数。为提高H13钢在挤压模具中的综合性能,延长其在生产实际中的使用寿命,同时也为激光熔覆工艺参数的优化提供理论和指导。本文介绍了利用正交试验分析激光熔覆工艺参数对熔覆尺寸的影响;借助光学显微镜(OM)和扫描电镜(SEM)分析了不同激光熔覆工艺对涂层宏观形貌以及组织形态的影响;借助X射线衍射仪(XRD)分析对涂层的成分进行定量分析;采用显微硬度计对各涂层截面沿层深方向的显微硬度进行表征;同时也对涂层的磨擦磨损性能以及常温疲劳性能进行表征。依据光学显微镜和扫描电镜分析涂层的组织形态和微观形貌,分析不同的激光熔覆工艺参数对熔覆涂层的宏观形貌影响,并对微观缺陷进行分析。采用数据分析方法PCA-TOPSIS法,依据单道熔覆的几何尺寸,优化出最优工艺参数。H13钢中添加Ni基合金的X射线衍射图谱表明,在Ni60A涂层主要由Cr23C6、γ(Fe-Ni)和Ni2Si等相组成,H13钢基体表面主要由CrFe4、Fe3C和α-Fe等相组成。涂层的显微硬度测试结果表明,涂层的显微硬度比基体有明显的提高,熔覆层截面显微硬度平均高达800HV,是基体的3~4倍。涂层的摩擦磨损实验表明,Ni60A涂层和H13钢基体在不同的载荷下,Ni60A涂层的磨损量并不随着载荷的增大而线性增大,当载荷从1200g增大到1600g时,磨损量明显变大;当载荷超出1600g时,磨损量基本不变。而H13钢的磨损量随着载荷的增大也随之呈现出线性变化,即H13钢的斜率是定值。涂层的耐腐蚀性能测试结果表明,Ni60A熔覆层的耐腐蚀性能比基体有明显的提高。为了修复失效的H13模具钢,引入了粉末吸热密度和稀释率的概念,探讨了两者的函数关系式,结果表明两者满足指数函数的关系,并通过实验得到了验证。H13钢表面熔覆Ni60A涂层的疲劳拉伸试验表明,不同的激光熔覆工艺参数下的疲劳寿命明显不同,稀释率在30%-35%之间的试样拉压疲劳寿命明显达到H13基体试样寿命的70%,为Ni基合金在稀释率可控性方面提出了理论指导。也为以后激光熔覆再制造技术在热挤压模修复中提高理论指导。
[Abstract]:H13 (4Cr5MoSiV1) alloy die steel is one of the most widely used die steels in hot work die steel. It is widely used in die casting die, forging die and hot extrusion die with high impact load. In the process of practical application, for example, the shunt die made of H13 steel plays an important role in the extrusion process of aluminum profile. The main failure forms are thermal fatigue wear and fracture. Laser cladding is an advanced surface strengthening technology, which can solve the problem of service life of split mode. According to the existing research reports, there is little research on how to obtain the laser cladding process parameters which can make the quality of the cladding coating better on the surface of H13 steel by cladding superalloy reinforcement phase, especially on how to obtain the laser cladding process parameters which make the quality of the cladding coating good. In this paper, the laser cladding of Ni-based alloy coating on H13 steel was carried out. The microstructure, phase composition and mechanical properties of the coating were analyzed. According to the cladding size of the coating, the optimum process parameters were obtained by using the PCA-TOPSIS method. In order to improve the comprehensive properties of H13 steel in extrusion die, prolong its service life in production practice, and provide the theory and guidance for the optimization of laser cladding process parameters. The influence of laser cladding process parameters on cladding size was analyzed by orthogonal test, and the effect of laser cladding process on the macroscopic morphology and microstructure of the coatings was analyzed by means of optical microscope (OM) and scanning electron microscope (SEM). The composition of the coating was quantitatively analyzed by means of X-ray diffraction (XRD), and the microhardness of the coating cross-sections along the depth of the coating was characterized by microhardness meter. At the same time, the friction and wear properties of the coating and the fatigue properties at room temperature were also characterized. The microstructure and microstructure of the coatings were analyzed by optical microscope and scanning electron microscope. The effects of different laser cladding parameters on the macroscopic morphology of the coatings were analyzed and the microdefects were analyzed. The data analysis method, PCA-TOPSIS, was used to optimize the X-ray diffraction patterns of Ni-base alloy in steel H13 according to the geometrical size of single-pass cladding. The Ni60A coating is mainly composed of Cr23C6, 纬 (Fe-Ni) and Ni2Si phases. The surface of H13 steel is mainly composed of CrFe4Fe3C and 伪 -Fe phases. The results of microhardness test show that the microhardness of the coating is obviously higher than that of the substrate. The average microhardness of the cladding layer is up to 800 HVV, which is 3 ~ 4 times of that of the substrate. The friction and wear experiments of Ni60A coating and H13 steel substrate show that the wear rate of Ni60A coating and H13 steel substrate does not increase linearly with the increase of load. When the load increases from 1200g to 1600g, the wear rate of Ni60A coating increases obviously, and when the load exceeds 1600g, the wear rate of Ni60A coating does not increase linearly with the increase of load. The amount of wear is basically unchanged. The wear rate of H13 steel changes linearly with the increase of load, that is, the slope of H13 steel is constant. The results of corrosion resistance test showed that the corrosion resistance of Ni60A cladding coating was better than that of substrate. In order to repair the failed H13 die steel, the concepts of powder endothermic density and dilution rate are introduced, and their functional relations are discussed. The results show that the relationship between them meets the exponential function. The fatigue tensile test of Ni60A coating on H13 steel surface shows that the fatigue life of Ni60A coating is obviously different with different laser cladding process parameters. The tensile and compressive fatigue life of the sample with dilution ratio between 30% and 35% is obviously 70 of that of the H13 matrix sample, which provides theoretical guidance for the controllability of the dilution rate of the Ni-based alloy. It also provides theoretical guidance for laser cladding and remanufacturing technology in hot extrusion die repair.
【学位授予单位】：江苏理工学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4

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