镍基合金激光熔覆再制造技术的工艺基础研究

发布时间：2018-09-03 19:38

【摘要】：再制造技术是以产品全生命周期设计和管理,以废旧机械零部件(如磨损等失效零件)作为对象,恢复废旧零部件原始尺寸、并且恢复甚至提升其服役性能的材料成形技术的统称。激光熔覆再制造是一种先进的再制造方法,激光熔覆技术利用高能激光束对基体和粉末进行局部加热,基体形成小区域熔池,粉末熔化后进入熔池形成冶金结合的先进制造技术。具有结合强度高,材料消耗少,热影响区小,涂层稀释率低,变形小,冷却速度快,组织致密,能制造梯度材料等特点。本文以镍基合金为熔覆粉末材料,Q235钢为基体,研究了激光熔覆再制造技术的工艺基础问题。激光熔覆是点到线再到面累积的过程,工艺参数之间的配合在激光熔覆中尤为重要,单道激光熔覆的研究是所有后续研究的基础。通过工艺参数单因素实验对激光功率、送粉速度、扫描速度和成形质量影响关系进行研究,得到单因素工艺参数对几何形貌的影响机理;通过多因素实验研究单道激光熔覆成形工艺参数影响规律,得到优化的匹配工艺参数,对金相组织和硬度进行测试,得到激光熔覆层不同区域性能。在激光熔覆表面修复技术中,面的熔覆是基础,面是由线组成的,不同轨迹之间搭接距离将对修复精度产生直接影响,搭接过程中会产生搭接不足、搭接过度和搭接良好等搭接现象,通过对相邻两道熔覆轨迹进行搭接,建立数学模型,计算搭接中心距,获得表面平整度高、成形性能优异的多道搭接熔覆层。激光熔覆是复杂的多场耦合过程,气-粉二相流场是激光熔覆材料输送的重要部分,气-粉流场的稳定性,均匀性将直接影响熔覆质量。针对送粉速度和气流量两个参数对粉末汇聚的影响进行了数值模拟研究,通过粉末力学性能和流变特性对粉末在气流中的受力进行机理研究,获得了影响激光熔覆气-粉二相流场的主要参数,并研究了熔深对粉末汇聚性的影响,为提高激光熔覆效率提供了支持。
[Abstract]:The technology of remanufacturing is to design and manage the whole life cycle of the product, take the parts of used machinery (such as worn out parts) as the object, and restore the original size of the used parts. And to restore or even improve its service performance of the material forming technology. Laser cladding remanufacturing is an advanced remanufacturing method. Laser cladding technology uses high energy laser beams to locally heat the matrix and powder, and the matrix forms a small melting pool. The advanced manufacturing technology of metallurgical combination is formed by the powder melting into the molten pool. It has the characteristics of high bonding strength, less material consumption, small heat affected zone, low dilution rate of coating, small deformation, fast cooling rate, compact microstructure, and can be used to manufacture gradient materials. In this paper, the technological foundation of laser cladding and remanufacturing technology was studied with nickel base alloy as cladding powder material and steel Q235 as substrate. Laser cladding is a process of point-to-line accumulation, and the coordination of technological parameters is particularly important in laser cladding. The study of single-channel laser cladding is the basis of all subsequent studies. The influence of laser power, powder feeding speed, scanning speed and forming quality was studied by single factor experiment, and the influence mechanism of single factor process parameters on geometric morphology was obtained. The influence law of single pass laser cladding process parameters was studied by multi-factor experiment. The optimized matching process parameters were obtained. The microstructure and hardness of the laser cladding layer were tested and the properties of different regions of laser cladding coating were obtained. In the laser cladding surface repair technology, the surface cladding is the foundation, and the surface is composed of lines. The overlap distance between different tracks will have a direct impact on the repair accuracy, and there will be lapping deficiencies in the lap process. By lapping the two adjacent cladding tracks, the mathematical model was established, and the center distance was calculated to obtain the multi-pass lap cladding coating with high surface smoothness and excellent formability. Laser cladding is a complicated multi-field coupling process. The gas-powder two-phase flow field is an important part of laser cladding material transportation. The stability and uniformity of gas-powder flow field will directly affect the cladding quality. In this paper, the effects of velocity of powder feeding and gas flow rate on powder aggregation are studied numerically. The mechanical properties and rheological properties of powder are used to study the mechanism of the mechanical properties of powder in the air flow. The main parameters affecting the gas-powder two-phase flow field of laser cladding are obtained, and the influence of penetration depth on powder convergence is studied, which provides support for improving laser cladding efficiency.
【学位授予单位】：新疆大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4

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