【作者】 赵青；

【导师】 杨慧君； 乔珺威；

【作者基本信息】 太原理工大学 ， 材料科学与工程， 2023， 硕士

【摘要】 高熵合金通常是指由五种或五种以上的主要成分,按等原子比或近等原子比组合而成的复合材料。但随着高熵合金研究的深入开展,其特殊的组合形式和优异的热力学性能也受到了科学家的普遍重视。同时,对高熵合金摩擦学特性的探讨也已形成了一项热门话题。但是到目前为止,对于高熵合金的摩擦学特性研究仍停留在常温干燥条件下,对各种环境中以及不同情况下的摩擦学特性研究知之甚少。众所周知,合金的耐磨性与合金的硬度成正比。因此,具有单相BCC结构的难熔高熵合金预计将具有优异的耐磨性。TiZrHfNbTa难熔高熵合金作为一种典型的难熔高熵合金体系,其具有较为优异的强度和塑性。为了TiZrHfNbTa难熔高熵合金的未来应用,研究其摩擦学性能成为了重中之重。同时,为了进一步提高TiZrHfNbTa难熔高熵合金体系的硬度,加入了V,将提高TiZrHfNbTaV难熔高熵合金的耐磨性。本文主要研究TiZrHfNbTa和TiZrHfNbTaV难熔高熵合金在室温不同条件下（干燥条件、去离子水以及模拟海水中）以及在高温下的摩擦学性能。本实验采用电弧熔炼技术,分别炼制了TiZrHfNbTa和TiZrHfNbTaV难熔高熵合金样品。使用XRD、SEM、金相显微镜和显微硬度计分析了TiZrHfNbTa和TiZrHfNbTaV难熔高熵合金的组织结构和硬度。在室温下,使用MFT-R4000高速往复摩擦磨损试验机分别研究了TiZrHfNbTa和TiZrHfNbTaV难熔高熵合金在干燥环境、去离子水环境和模拟海水环境中的摩擦学性能。在高温下,使用HT-4001高温摩擦磨损试验机分别研究了TiZrHfNbTa和TiZrHfNbTaV难熔高熵合金在不同温度下的摩擦学性能。此外,还通过SEM和XPS研究了其磨损机制。研究结果表明:（1）TiZrHfNbTa和TiZrHfNbTaV难熔高熵合金均为单相体心立方（BCC）结构,组织为典型的枝晶结构,且元素成分比较均匀。（2）TiZrHfNbTa难熔高熵合金的硬度～390 HV。而在TiZrHfNbTa难熔高熵合金加入V后,会使TiZrHfNbTaV难熔高熵合金的硬度提高至～490 HV,将提高TiZrHfNbTaV难熔高熵合金的耐磨性。（3）TiZrHfNbTa难熔高熵合金在室温下摩擦磨损时,在5N、10N和15N的载荷下,磨损率均是先增大后减小,在10 N时磨损率最高为3.02×10^-4mm³/（Nm）。磨损机制主要为磨粒磨损和黏着磨损,未发生氧化磨损。此外,在模拟海水中时,磨损表面的Cl元素含量较低,且未发现腐蚀现象。与TiZrHfNbTa难熔高熵合金相似,TiZrHfNbTaV难熔高熵合金室温磨损率也是先增大后减小,在10 N时达到最大值。且磨损率均低于TiZrHfNbTa难熔高熵合金,表明V的加入提高了TiZrHfNbTaV难熔高熵合金的硬度,从而提高了TiZrHfNbTaV难熔高熵合金的室温耐磨性。（4）通过摩擦热计算,TiZrHfNbTa难熔高熵合金和TiZrHfNbTaV难熔高熵合金在高温条件下摩擦磨损时,摩擦生热引起的温升均可忽略不计。TiZrHfNbTa难熔高熵合金在高温下,400℃后发生氧化磨损。该氧化物膜主要由TiO₂、ZrO₂、NbO₂、Nb₂O₅等金属氧化物组成。TiZrHfNbTaV难熔高熵合金在高温下,主要磨损机理为100℃～300℃的磨粒磨损和黏着磨损,300℃后发生氧化磨损,500℃时形成致密的氧化膜。V的加入会降低TiZrHfNbTaV难熔高熵合金的抗氧化性,使其在300℃时便发生氧化。这在高温摩擦磨损过程中是有利的,致密的氧化膜硬度较高且可以保护基体,从而提高TiZrHfNbTaV难熔高熵合金的高温耐磨性。更多还原

【Abstract】 High entropy alloys are generally alloys composed of five or more main elements in equal or nearly equal atomic ratios.With the further development of high entropy alloys,their unique microstructure and excellent mechanical properties have attracted the wide attention of researchers.At the same time,the research of tribological properties of high entropy alloys has become a hot topic.But up to now,the research on the tribological properties of high entropy alloys is still confined to the dry environment at room temperature,and little is known about the tribological properties at different environments and temperatures.It is well known that the wear resistance of alloys is directly proportional to the hardness of alloys.Therefore,refractory high entropy alloys with single-phase BCC structure are expected to have excellent wear resistance.TiZrHfNbTa refractory high entropy alloy,as a typical refractory high entropy alloy system,has excellent strength and plasticity.For the future application of TiZrHfNbTa refractory high entropy alloy,the study of its tribological properties has become a priority.Meanwhile,in order to further improve the hardness of TiZrHfNbTa refractory high entropy alloy system,V is added,which is expected to improve the wear resistance of TiZrHfNbTaV refractory high entropy alloy system.This paper mainly studies the tribological properties of TiZrHfNbTa and TiZrHfNbTaV refractory high entropy alloys at different room temperature（dry conditions,deionized water and simulated seawater）and at high temperature.In this experiment,the refractory high entropy alloy samples of TiZrHfNbTa and TiZrHfNbTaV were fabricated by arc melting technology.The microstructure and hardness of TiZrHfNbTa and TiZrHfNbTaV refractory high entropy alloys were analyzed by XRD,SEM,metallographic microscope and microhardness tester.The tribological properties of TiZrHfNbTa and TiZrHfNbTaV refractory high entropy alloys in dry environment,deionized water environment and simulated seawater environment were studied using MFT-R4000 high speed reciprocating friction and wear testing machine at room temperature.The tribological properties of TiZrHfNbTa and TiZrHfNbTaV refractory high entropy alloys at different temperatures（25℃,100℃,200℃,300℃,400℃,500℃and 600℃）were studied using HT-4001 high temperature friction and wear tester.In addition,the wear mechanism was studied by SEM and XPS.The results show that:（1）TiZrHfNbTa and TiZrHfNbTaV refractory high entropy alloys both have single-phase body-centered cubic（BCC）structure,typical dendrite structure,and relatively uniform element composition.（2）The hardness of TiZrHfNbTa refractory high entropy alloy is～390 HV.The hardness of TiZrHfNbTaV refractory high entropy alloy is increased to～490 HV after adding V,and the wear resistance of TiZrHfNbTaV refractory high entropy alloy is improved.（3）During friction and wear of TiZrHfNbTa refractory high entropy alloy at room temperature,the wear rate increases first and then decreases at 5N,10N and 15N loads,and the highest wear rate is 3.02×10^-4 mm³/（Nm）at 10N.The wear mechanism is mainly abrasive wear and adhesive wear,but no oxidation wear occurs.In addition,in simulated seawater,the content of Cl on the worn surface was low and no corrosion was observed.Similar to TiZrHfNbTa refractory high entropy alloy,the room temperature wear rate of TiZrHfNbTaV refractory high entropy alloy also increases first and then decreases,reaching the maximum value at 10 N.The wear rate is lower than that of TiZrHfNbTa refractory high entropy alloy,indicating that the addition of V improves the hardness of TiZrHfNbTaV refractory high entropy alloy,and thus improves the wear resistance of TiZrHfNbTaV refractory high entropy alloy at room temperature.（4）According to the calculation of frictional heat,the temperature rise caused by frictional heat generation of TiZrHfNbTa refractory high entropy alloy and TiZrHfNbTaV refractory high entropy alloy can be ignored during friction and wear at high temperature.The oxidation wear of TiZrHfNbTa refractory high entropy alloy occurs at high temperature and 400℃.The oxide film is mainly composed of TiO₂,ZrO₂,NbO₂,Nb₂O₅ and other metal oxides.The main wear mechanism of TiZrHfNbTaV refractory high entropy alloy at high temperature is abrasive wear and adhesive wear at 100℃～300℃,oxidative wear at 300℃,and dense oxide film at 500℃.The addition of V can reduce the oxidation resistance of TiZrHfNbTaV refractory high entropy alloy and make it oxidize at 300℃.This is advantageous in the process of high temperature friction and wear.The dense oxide film has higher hardness and can protect the matrix,thus improving the high temperature wear resistance of TiZrHfNbTaV refractory high entropy alloy.更多还原