电机主轴激光修复层组织及断裂研究

发布时间：2018-04-27 13:00

本文选题：电机主轴 + 激光修复　；参考：《山东大学》2015年硕士论文

【摘要】：轴类零件的使用在现代工业中占有举足轻重的地位,随着现代工业的不断发展,轴类零件的工作环境日趋复杂,报废率也日趋提高。激光修复具有高能量高密度,热输入可控性好,加工位置可精确定位的特点,可通过与计算机数控技术的结合,实现轴类零件修复的快速高效。因此采用激光修复已成为轴类零件修复的趋势。本课题针对电机主轴在激光修复后出现断裂失效的问题,对电机主轴激光修复层进行显微组织微观形貌、物相特征以及断裂机制的分析研究,以有效改进激光修复工艺,指导工厂生产。采用光学显微镜及显微硬度仪对修复层显微组织形貌特征及显微硬度分布特征进行观察分析,修复层根据显微组织形貌特征划分为熔覆区、热影响区以及过渡区。其中熔覆区呈现类共晶组织特征,依次形成平面晶、胞状晶及树枝晶等晶态,树枝晶晶粒粗大,主干较长且二次横枝形核较多,对熔覆区韧性具有一定程度的减弱作用。热影响区完全重结晶区为晶粒细小的铁素体和珠光体,而部分重结晶区残余先共析铁素体分布明显。从熔覆区中心到母材方向上显微硬度整体呈减小趋势,其中熔覆区显微硬度远远高于热影响区,熔覆区树枝晶显微硬度最高,平面晶处显微硬度最小。采用XRD衍射仪对熔覆区进行物相组成分析,其物相组成主要为(Fe, Cr)固溶体(α相)和Cr-Fe固溶体(δ相),且(Fe, Cr)固溶体较多。其次还含有少量的固溶体CrFe4、Fe-Cr-Ni、(Fe, Ni)等以及金属间化合物Cr7C3。Cr-Fe固溶体及CrFe4固溶体较为硬脆,加速了合金的脆化。采用扫描电子显微镜及能谱分析仪对修复层微观组织形貌组成,裂纹萌生机制及断口表明形貌进行分析研究,熔覆区平面晶为单一物相的(Fe, Cr)固溶体(α相),胞状晶、树枝晶基体均为(Fe, Cr)固溶体,浮凸处主要物相为Cr-Fe固溶体。显微裂纹类型为多边化裂纹,萌生于过渡区熔覆区一侧或母材一侧。(Fe, Cr)固溶体处或Cr-Fe固溶体与(Fe, Cr)固溶体两相界面处形成的多边化边界为显微裂纹萌生的起源地,其扩展方向有两种,分别是与过渡区界面方向平行扩展和沿熔覆区厚度方向,与界面大致垂直扩展。断口宏观形貌特征分为镜面区、雾状区及锯齿带三个特征区域,其微观形貌主要由准解理(QC)、沿晶(IG)、及少量的韧窝(DR)组成。雾状区主要为沿晶断裂(IG)和韧窝断裂(DR)。锯齿带微观形貌特征与雾状区相似。但区别为锯齿带处韧窝断裂是断裂机制的主体。
[Abstract]:The use of shaft parts plays an important role in modern industry. With the development of modern industry, the working environment of shaft parts is becoming more and more complex, and the scrapping rate is increasing day by day. Laser repair has the characteristics of high energy density, good controllability of heat input and precise location of machining position. It can be quickly and efficiently repaired by combining with computer numerical control technology. Therefore, laser repair has become the trend of shaft parts repair. Aiming at the fracture failure of motor spindle after laser repair, the microstructure, phase characteristics and fracture mechanism of the laser repair layer of motor spindle are analyzed and studied in order to improve the laser repair technology effectively. Direct factory production. The microstructure and microhardness distribution of the repair layer were observed and analyzed by optical microscope and microhardness analyzer. The repair layer was divided into cladding zone, heat affected zone and transition zone according to the microstructure characteristics. The cladding zone is characterized by eutectic structure, such as plane crystal, cellular crystal and dendritic crystal. The dendritic grain is coarse, the main trunk is longer and the secondary transverse branch nucleus is more. The cladding zone has a certain degree of weakening effect on the toughness of cladding zone. The complete recrystallization zone in the heat affected zone is composed of fine ferrite and pearlite, while the residual proeutectoid ferrite in some recrystallized regions is obvious. The microhardness of cladding zone is much higher than that of heat-affected zone from the center of cladding zone to the direction of base metal. The microhardness of dendrite in cladding zone is the highest and the microhardness at plane crystal is the smallest. The phase composition of the cladding zone was analyzed by XRD diffractometer. The phase compositions were mainly Fe, Cr) solid solution (伪 phase) and Cr-Fe solid solution (未 phase), and there were more Fe, Cr solid solution. Secondly, it also contains a small amount of solid solution, such as CrFe4FE-Fe-Cr-NiOFe, Ni), and the intermetallic compounds Cr7C3.Cr-Fe solid solution and CrFe4 solid solution are hard and brittle, which accelerates the embrittlement of the alloy. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to analyze the microstructure, crack initiation mechanism and fracture surface of the repair layer. The dendritic matrix is Cr-Fe solid solution, and the main phase in the convex part is Cr-Fe solid solution. The type of microcrack is multilateral crack, and the multilateral boundary formed at the side of the cladding zone or the side of the base metal, or at the interface between Cr-Fe solid solution and Fe, Cr) solid solution is the origin of micro-crack initiation. There are two kinds of propagation directions, which are parallel to the transition zone interface, along the cladding zone thickness, and roughly vertical to the interface. The macroscopic morphology of the fracture is divided into three characteristic regions: mirror region, fog zone and serrated zone. The microscopic morphology of the fracture is mainly composed of quasi cleavage QC, intergranular IGC, and a small amount of dimple DRs. The foggy zone is mainly intergranular fracture (IGR) and dimple fracture (DRV). The microscopic morphology of the zigzag zone is similar to that of the foggy zone. But the dimple fracture in the zigzag belt is the main part of the fracture mechanism.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM307;TN249

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