摘 要

钛合金因为其比强度高，密度低等特点，成为了航空航天领域的优质应用材料，其使用含量已经成为一个国家航空发动机制造技术先进与否的重要衡量指标。但是钛合金存在着硬度相对较低，耐磨性和高温抗氧化性较差等缺陷，影响了其作为关键零部件的应用范围。高熵合金作为一种先进的新型材料以其优异的性能迅速成为了多个领域的研究重点，特别是其较高的硬度和良好的耐磨性，高温抗氧化性可以与钛合金优势互补，两种材料复合具有很广阔的研究前景。因此在钛合金表面制备高熵合金涂层有望改善钛合金部件的耐磨性和高温抗氧化性，拓展其应用领域。

故本文对实验室获得的Ti-6Al-4V合金表面激光熔覆AlCoCrFeNiTix高熵合金涂层试样的耐磨性和高温抗氧化性进行测试与分析，并与未处理的Ti-6Al-4V合金进行对比，探讨其应用的可能性。

研究结果表明：（1）常温下，AlCoCrFeNiTix高熵合金涂层的耐磨性能远优于TC4钛合金，表现为相同实验条件下涂层体积磨损量0.017mm³，仅为母材体积磨损量0.632mm³的1/36，即耐磨性提高约35倍。涂层的磨损机理主要为粘着磨损，母材的磨损机理为磨粒磨损。（2）600℃的非连续性氧化试验表明，TC4钛合金的等温氧化增重速率为0.942mg/cm²，AlCoCrFeNiTix高熵合金涂层的等温氧化增重速率为0.238mg/cm²，氧化动力曲线遵循抛物线规律，AlCoCrFeNiTix高熵合金涂层的氧化速率指数约为5.896，近似遵循六次方抛物线规律，氧化速率指数大于2说明涂层合金形成的致密氧化膜相比钛合金形成的松散TiO₂氧化膜能够更好地保护母材材料不会遭到氧元素的进一步氧化侵蚀；XRD结果和氧化膜表面形貌显示AlCoCrFeNiTix高熵合金涂层形成的氧化膜薄且致密，表明了该涂层合金具有良好的抗氧化性，能够明显改进钛合金表面的抗氧化性差的缺陷。

关键词：TC4钛合金；高熵合金；抗氧化性；耐磨性

Abstract

Titanium alloy has become a high-quality application material in the aerospace industry because of its high specific strength and low density. Its use content has become an important measure of the advanced or advanced national aero-engine manufacturing technology. However, titanium alloys have defects such as relatively low hardness, poor wear resistance and high temperature oxidation resistance, which affect their application as key components. As an advanced new material, high-entropy alloy has quickly become the research focus of many fields with its excellent performance, especially its high hardness and good wear resistance. The high-temperature oxidation resistance can complement the advantages of titanium alloy. The combination of two materials has a broad research prospect. Therefore, the preparation of high-entropy alloy coating on the surface of titanium alloy is expected to improve the wear resistance and high-temperature oxidation resistance of titanium alloy parts, and expand its application fields.

Therefore, this paper tests and analyzes the wear resistance and high temperature oxidation resistance of laser-clad AlCoCrFeNiTix high-entropy alloy coating samples on Ti-6Al-4V alloy surface obtained by laboratory, and with untreated Ti-6Al-4V alloy. Compare and explore the possibilities of its application.

The results show that: (1) At normal temperature, the wear resistance of AlCoCrFeNiTix high-entropy alloy coating is much better than that of TC4 titanium alloy. It shows that the volume wear of the coating is 0.017mm3 under the same experimental conditions, only the volume wear of the base material is 0.632mm3. 1/36, that is, the wear resistance is increased by about 35 times. The wear mechanism of the coating is mainly adhesive wear, and the wear mechanism of the base material is abrasive wear. (2) The discontinuous oxidation test at 600 °C showed that the isothermal oxidation weight gain rate of TC4 titanium alloy was 0.942 mg/cm2, and the isothermal oxidation weight gain rate of AlCoCrFeNiTix high entropy alloy coating was 0.238 mg/cm2, and the oxidation power curve followed. Parabolic law, the oxidation rate index of AlCoCrFeNiTix high-entropy alloy coating is about 5.896, which approximates the sixth-order parabolic law. The oxidation rate index is greater than 2, indicating that the dense oxide film formed by the coating alloy can form a loose TiO2 oxide film formed by titanium alloy. Better protection of the base material will not be further oxidized by oxygen; XRD results and surface morphology of the oxide film show that the oxide film formed by the AlCoCrFeNiTix high-entropy alloy coating is thin and dense, indicating that the coating alloy has good properties. The oxidation resistance can significantly improve the defect of the oxidation resistance of the titanium alloy surface.

Key words： TC4 titanium alloy;; high entropy alloy; oxidation resistance; wear resistance

目 录

第1章 绪 论 7

1.1 钛合金应用及其局限性 7

1.2钛合金表面改性 8

1.3高温氧化理论简介 9

1.3.1高温氧化动力学基础 9

1.3.2高温氧化的动力学规律 9

1.3.3高温氧化的研究方法 9

1.4材料磨损和耐磨性简介 10

1.4.1磨损的定义和分类 10

1.4.2材料耐磨性的评定 10

1.5高熵合金涂层表面性能简介 10

1.6本文的主要研究目的及内容 11

1.6.1研究目的及意义 11

1.6.2研究内容 12

第2章 实验材料及方法 12

2.1实验材料 13

2.1.1基体材料 13

2.1.2 熔覆材料制备 13

2.2 激光熔覆实验 13

2.3涂层的性能试验 14

2.3.1 微观组织 14

2.3.2硬度试验 15

2.3.3耐磨性试验 15

2.3.4高温抗氧化试验 15

第3章 激光熔覆AlCoCrFeNiTix高熵合金涂层的性能分析 16

3.1引言 17

3.2AlCoCrFeNiTix高熵合金涂层的宏观形貌和显微组织 17

3.2.1宏观形貌 17

3.2.2显微组织 18

3.3 AlCoCrFeNiTix高熵合金涂层的硬度及耐磨性分析 19

3.3.1显微硬度分析 19

3.3.2摩擦系数分析 19

3.3.3摩擦磨损量分析 20

3.3.4表面磨损形貌分析 21

3.4 AlCoCrFeNiTix高熵合金涂层的高温抗氧化性分析 22

3.4.1氧化动力曲线 22

3.4.2 氧化速率指数分析 23

3.4.3氧化产物分析 24

3.4.4 氧化膜表面形貌分析 24

3.5本章小结 25

第4章 结 论 26

参 考 文 献 27

致 谢 29

第1章 绪 论

1.1 钛合金应用及其局限性

钛合金是在工业纯钛中加入少量其他合金元素（如Al、Si、V、Mo、Cu等）合金化而成的，其目的是为了提高Ti的使用范围。相对于纯钛，钛合金具有更好的耐蚀性和耐热性等特点，其作为比重轻、强度高的优质材料被广泛应用于石油化工、航空航天、造船工业、汽车工业等多个领域，尤其是在航空航天领域，钛合金的含量多少已经成为发动机性能的重要指标。钛合金根据退火组织分为α钛合金（型号TA），β钛合金（型号TB）和α＋β钛合金（型号TC）。其中α钛合金组织稳定，具有良好的焊接性和耐腐蚀性，但强度低和机械加工困难，β钛合金具有高强度但组织不稳定耐热性差。α＋β钛合金兼有两者优点，表现优异综合力学性能，强度高和抗腐蚀性好，是最广泛使用的一种钛合金,其产量占据钛合金50%以上^[1]。但钛合金摩擦系数大^[2]、硬度低^[3]、易磨损^[4-5]、高温抗氧化性差^[6]等缺点，阻碍钛合金作为关键运动零部件（发动机涡轮叶片、活塞环、转子盘、阀门等）的广泛应用。钛合金作为关键运动零部件（压气机机闸，发动机活塞及阀门等），其工作环境复杂，不仅需要具有较好耐磨性能，而且需要在高温环境下具有耐高温腐蚀能力。在保证钛合金综合力学性能条件下，表面改性技术是改善钛合金缺点经济有效的方法之一。

1.2钛合金表面改性