论文总字数：21166字

摘 要

在模具修复研究中，我们发现激光熔覆对5CrNiMo修复具有良好效果。激光熔覆过程中影响激光熔覆质量的因素有很多,并且各个影响因素之间还会相互作用，关联复杂。因此，本文首先确定了熔覆层组织的几个影响因素，采用控制变量的研究方法，主要把激光功率、扫描速度、送粉量、搭接率几个主要因素作为变量，研究在什么样的条件下，得出的激光熔覆层的性质最优良，来提高生产效益，节约生产成本。本文采用控制变量法使用Laserline4000W半导体激光器在5CrNiMo热作模具钢表面用不同的激光功率、扫描速度、送粉量以及搭接率制备单道熔覆层及多道熔覆层，通过体式显微镜、光学显微镜、维氏显微硬度计及Nano Measurer软件研究熔覆层组织的宏观形貌、显微组织、显微硬度及晶粒大小变化，分析激光功率对熔覆层的组织变化的影响，总结其变化规律。

通过实验研究发现，当其他条件不变时：激光功率越大，功率密度越大，熔宽，厚度越大，稀释率逐渐增加，硬度逐渐增大；扫描速度越大，熔宽、厚度越低，稀释率逐渐增加，选择适当的扫描速度，可以提高熔覆层硬度；送粉量越大，熔宽、厚度以及硬度和稀释率均降低。搭接率适当的熔覆层，搭接重熔部分，晶粒细化，组织结构变得致密，熔覆层的硬度增大。熔覆层组织从底部到顶部的显微组织变化为底部形成大量的柱状晶和枝晶，中部长的枝晶变短，到熔覆层顶部，逐渐转变为大量的等轴晶和共晶组织。当激光功率增大时，晶粒变大；当扫描速度增大时，激光功率变小；当送粉量变大时，晶粒缓慢增大。

关键词：激光熔覆 5CrNiMo 显微组织 工艺参数

Effects of laser processing on microstructure and properties of coatings by laser cladding on 5CrNiMo steel

Abstract

In the study of mold repair, we found that laser cladding has a good effect on 5CrNiMo repair. There are many factors that affect the quality of laser cladding in the laser cladding process, and each influencing factor will also interact with each other, and the correlation is complex. Therefore, this article first identified several factors affecting the microstructure of the cladding layer. Using the research method of controlled variables, the main factors of laser power, scanning speed, powder delivery, and lap ratio were used as variables to study what kind of Under the conditions, the laser cladding layer obtained has the best properties to improve production efficiency and save production costs. In this paper, a single-channel cladding layer and multiple cladding layers were prepared on a 5CrNiMo hot work die steel surface using controlled variable method using Laserline 4000W semiconductor laser with different laser power, scanning speed, powder feed rate and lapping rate, through a stereomicroscope, optical Microscope, Vickers microhardness tester and NanoMeasurer software were used to study the macroscopic morphology, microstructure, microhardness and crystallite size changes of the cladding microstructure. The effects of laser power on the microstructure change of the cladding layer were analyzed, and the changes were summarized. law.

Through experimental studies, it was found that when other conditions are constant: the greater the laser power, the greater the power density, the wider the melt, the greater the thickness, the dilution rate gradually increases, and the hardness gradually increases; the larger the scanning speed, the lower the melting width and thickness The dilution rate gradually increases. Selecting the appropriate scanning speed can increase the hardness of the cladding layer; the greater the amount of powder delivered, the lower the melting width, thickness, hardness, and dilution rate. The cladding layer with an appropriate lap rate overlaps the remelted portion, refines the grain, and the microstructure becomes denser, and the hardness of the cladding layer increases. The microstructure of the cladding layer changes from the bottom to the top, forming a large number of columnar crystals and dendrites at the bottom. The dendrites of the middle ministers become shorter, and they gradually transform into a large number of equiaxed crystals and eutectic structures at the top of the cladding layer. When the laser power increases, the crystal grains become larger; when the scanning speed increases, the laser power becomes smaller; when the powder feeding amount becomes larger, the crystal grains increase slowly.

Key words: Laser Cladding；5CrNiMo；Microstructure；Process Parameters；

目录

摘要 I

Abstract II

第一章 绪论 1

1.1 研究背景及意义 1

1.2 激光技术及其应用 1

1.3 激光熔覆技术的研究分析 2

1.4 5CrNiMo概述 3

1.5 本课题的研究目标及研究内容 4

第二章 实验材料与方法 5

2.1 实验材料 5

2.2实验设备、过程和分析方法 5

第三章 激光加工工艺参数研究 9

3.1 控制变量法实验方案 9

3.2 熔覆层的性能评估 10

3.3 本章小结 19

第四章 熔覆层显微组织分析 21

4.1 激光功率 21

4.2 扫描速度 22

4.3 送粉量 24

4.4 搭接率 26

4.5 本章小结 27

第五章 结论与展望 28

5.1实验结论 28

5.2展望 28

参考文献 30

致谢 31

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