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作者简介:

勾俊峰,男,1987年出生,博士,讲师。主要研究方向为耐磨耐腐蚀涂层。E-mail:goujunfeng@gdut.edu.cn;

刘江文(通信作者),男,1980年出生,博士,副教授,硕士研究生导师。主要研究方向为电加工、电火花涂层。E-mail:fejwliu@scut.edu.cn;

王铀,男,1954年出生,博士,教授,博士研究生导师。主要研究方向为热喷涂、纳米改性及摩擦磨损。E-mail:wangyou@hit.edu.cn

中图分类号:TG174

DOI:10.11933/j.issn.1007−9289.20211019002

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目录contents

    摘要

    Cr2O3对 Al2O3-Cr2O3复合涂层与高硬度陶瓷接触时的摩擦磨损行为及磨损机制的影响尚未揭示。采用大气等离子喷涂的方法制备 Cr2O3含量不同的 Al2O3-Cr2O3复合涂层以研究 Cr2O3的影响机制。试验结果表明:Cr2O3明显减少了涂层的微观孔隙;复合涂层中 α-Al2O3 / γ-Al2O3的相对含量比明显高于 Al2O3涂层中的 37%;Al2O3-40%Cr2O3涂层的硬度与 Al2O3涂层相比提高了 48%,断裂韧性是 Al2O3涂层的 2 倍多;当载荷为 5 N、10 N 和 15 N 时,Al2O3-40%Cr2O3复合涂层的摩擦因数最低,磨损率依次降低 60%、85% 和 79%。但是当载荷为 20 N 时,Al2O3-20%Cr2O3复合涂层的摩擦因数最低,磨损率降低了 50%。微观脆性断裂是涂层的主要磨损机制。复合涂层耐滑动磨损性能与 Cr2O3含量及磨损条件是密切相关的。微观结构、硬度、断裂韧性、导热系数等是影响 Al2O3-Cr2O3 复合涂层耐磨损性能的重要因素。研究结果可为高耐磨性 Al2O3基涂层的设计和应用提供指导。

    Abstract

    The effect of Cr2O3 on the friction and wear behaviour and wear mechanism of Al2O3-Cr2O3 composite coating sliding against ceramic ball with high hardness is still unknown. Atmospheric plasma spraying is used to deposit Al2O3-Cr2O3 composite coatings with different contents of Cr2O3 to reveal its influential mechanism. The experimental results show that Cr2O3 decreases the voids in the coating obviously. The relative α-Al2O3 / γ-Al2O3 content ratios in the composite coatings are larger than 37%. The micro-hardness of Al2O3-40%Cr2O3 composite coating increases by 48% compared with Al2O3 coating, the fracture toughness of which is twice as large as that of Al2O3 coating. Al2O3-40%Cr2O3 composite coating has lower friction factor and wear rates when the wear loads are 5 N, 10 N and 15 N than Al2O3 coating, their wear rates decrease by 60%, 85% and 79% compared with those of Al2O3 coating. But when the wear load is 20 N, Al2O3-20%Cr2O3 composite coating has lower friction factor than Al2O3 coating, its wear rate decreases by 50% compared with that of Al2O3 coating. The main wear mechanism of the coatings is micro-fracture. The wear resistance of the composite coating is determined by the content of Cr2O3 and wear condition. Microstructure, hardness, fracture toughness and coefficient of thermal conductivity are important factors affecting the wear resistance of Al2O3-Cr2O3 composite coating. The research results can provide guidance for the design and application of Al2O3-based coating with high wear resistance.

  • 0 前言

  • 随着科学技术的进步,航空航天、海洋工程、地面工程等领域的装备在不断更新换代,很多关键零部件的使用环境越来越苛刻,需要在抗高温、耐磨损和耐腐蚀等方面具备更高的使用性能[1-3]。在一些极端环境条件下,制备零部件所用基体材料的性能已经限制了装备技术参数的进一步提高。表面工程技术能够在保证零部件基体材料性能的基础上进一步提高其使用性能[4]。热喷涂是一类重要的表面工程技术,具有高效、低成本的优势,能够在金属或者非金属基体上沉积不同成分的防护涂层,提高零部件使用寿命[5]。大气等离子喷涂技术的射流温度高,熔滴运动速度快,涂层较为致密,是制备高性能陶瓷涂层的重要方法[6]

  • Al2O3 具有优异的电绝缘性能、高的化学稳定性、硬度、耐磨性和耐腐蚀性[7]。因此,Al2O3 被用作功能涂层或者防护涂层,以提高金属基体的绝缘性能、耐磨损性和耐腐蚀性等。尽管Al2O3 涂层具有诸多优势,但是Al2O3 自身相稳定性差的问题限制了它的应用。α-Al2O3是Al2O3 的高温稳定相,但是在喷涂过程中由于熔滴的非平衡凝固,最终在涂层中形成大量的亚稳Al2O3[8]。γ-Al2O3 是最为常见的Al2O3 亚稳相,γ-Al2O3 的密度和热导率均低于 α-Al2O3,比热容高于 α-Al2O3 [9-10]。因此,α-Al2O3 和 γ-Al2O3 之间的相变会引起涂层内应力场和导热系数的变化,降低涂层的力学性能、抗热震性能和耐磨损性能等[11]

  • 科研人员通过在Al2O3 涂层中添加不同的氧化物来改善涂层的性能。 DEJANG等 [12]制备了Al2O3-TiO2 复合涂层,发现纳米TiO2 提高了Al2O3 涂层的断裂韧性和耐磨性,但是不能稳定 α-Al2O3 相。在Al2O3涂层中引入ZrO2,同样是提高了涂层的断裂韧性,但是对于稳定 α-Al2O3 相没有显示出较为明显的作用[13]。Cr2O3 是一种重要的耐磨耐腐蚀涂层材料,具有和 α-Al2O3 相同的晶体结构[14]。通过在Al2O3涂层中添加一定含量的Cr2O3,可以有效稳定涂层中的 α-Al2O3[15]

  • ZHAO等[15]研究Cr2O3 含量对Al2O3-Cr2O3 复合涂层晶体结构和线膨胀系数的影响,发现Cr2O3 在Al2O3 中的固溶导致Al2O3 晶体在c轴方向发生明显的晶格畸变,降低了其线膨胀系数。YANG等[16]研究发现,Al2O3-Cr2O3 复合涂层比Al2O3 和Cr2O3 涂层具有更好的综合力学性能,主要归因于复合涂层内高的层间结合以及低的孔隙率。在此基础上,YANG等[17]进一步研究Al2O3-Cr2O3 复合涂层与石墨对磨时的耐滑动磨损性能,发现Cr2O3 含量为90%时,复合涂层的耐磨性更好。以上相关研究揭示了Cr2O3 含量对复合涂层相结构、力学性能和耐滑动磨损性能的影响,但是仍然存在一些问题有待进一步研究。目前有关Al2O3-Cr2O3 复合涂层的研究中Cr2O3 的成分变化梯度较大,Cr2O3 含量较高,不能系统地评价Cr2O3 含量对富Al2O3 的Al2O3-Cr2O3 复合涂层结构和力学性能的影响。此外,对富Al2O3 的Al2O3-Cr2O3 复合涂层与高硬度陶瓷件对磨时的摩擦磨损行为的研究非常有限,尤其是有关Cr2O3 含量梯度增加对Al2O3-Cr2O3 复合涂层与陶瓷对磨时的耐滑动磨损性能的影响规律还未见详细报道。

  • 基于上述问题,鉴于Al2O3 优异的综合性能,本文设计并制备富Al2O3的Al2O3-Cr2O3 复合涂层。通过机械混粉的方法制备Al2O3-Cr2O3 复合粉体;采用大气等离子喷涂的方法制备涂层;采用滑动磨损试验机研究涂层的摩擦磨损行为。研究Cr2O3 含量梯度增加对复合涂层微观结构、力学性能和干滑动摩擦磨损行为的影响,优化Cr2O3 含量,揭示涂层磨损机制,为制备高耐磨性复合涂层提供理论指导。

  • 1 试验材料和试验方法

  • 1.1 复合粉体和涂层的制备

  • 试验所用粉体材料为商用Al2O3 和Cr2O(霈泽3材料科技有限公司,纯度99.9%),均采用机械破碎的方法造粒。Al2O3 和Cr2O3 原料粉体形貌如图1所示,均为不规则的多边形颗粒。Al2O3 和Cr2O3 的粉体粒径均介于15~55 μm。

  • 图1 原始粉体形貌

  • Fig.1 Morphology of the raw powders

  • 按照重量比例称取Al2O3和Cr2O3,装入不锈钢球磨罐,放入全方位行星球磨机,利用机械混粉的方法制备Cr2O3 含量不同的Al2O3-Cr2O3 复合粉体。控制球磨机转速为100~200r/min,混粉时间120min,最终制备得到复合粉体。试验所用复合粉体的具体成分如表1所示。

  • 表1 Al2O3-Cr2O3复合粉体成分(质量分数/wt.%)

  • Table1 Composition of Al2O3-Cr2O3 composite powders (wt.%)

  • 为分析复合粉体中各组分的分布情况,对Al2O3-40%Cr2O3 复合粉体进行面扫描分析,结果如图2所示。从图中可以看出,复合粉体颗粒形貌与原始粉体相比没有变化,仍为不规则多边形。从面扫描元素分布图上可以看出,Al元素和Cr元素的分布比较均匀,说明Cr2O3 均匀分布在Al2O3 粉体中,所制备的复合粉体具有较好的成分分布。

  • 采用配备F4MB-XL喷枪的Sulzer Metco大气等离子喷涂系统制备涂层。基体采用尺寸为 φ30mm× 6mm的304不锈钢圆片,喷涂前基体表面经过喷砂和超声清洗处理。黏结层为镍基涂层,利用商用40~105 μm的NiCrAlY粉体制备,黏结层厚度控制到80 μm。黏结层厚度的选择主要依据何艳玲等[14]对等离子喷涂Al2O3 与Cr2O3 涂层的研究内容和张健等[18]关于Al2O3 基复合涂层的研究内容。面层利用表1给出的Al2O3和Al2O3-Cr2O3 复合粉体制备,面层厚度控制到200 μm。为了避免面层厚度变化对涂层结合强度及耐磨损性能的影响,本文所有面层的厚度均控制到200 μm。黏结层和面层喷涂参数如表2所示。

  • 图2 Al2O3-40%Cr2O3复合粉体的形貌以及成分分布

  • Fig.2 Morphology and composition distribution of Al2O3-40%Cr2O3 composite powder

  • 表2 喷涂参数

  • Table2 Thermal spraying parameters

  • 1.2 试验方法

  • 采用扫描电子显微镜观察粉体和涂层的微观形貌。采用X射线衍射仪测试涂层物相组成,扫描2θ 范围为10°~70°,扫描速率6 (°)/min。采用激光共聚焦显微镜测试不同涂层的表面粗糙度。采用维氏显微硬度计测试涂层硬度,加载载荷300g,加载时间和保载时间均为15s。观察压痕形貌,利用式(1) 计算涂层断裂韧性[19]

  • KC=0.0515Pc1.5
    (1)
  • 式中,Kc为断裂韧性(MPa·m 0.5),P 为载荷(N), c 为裂纹长度(m)。尽管涂层结合强度是影响涂层摩擦磨损行为的一个因素,但是本文摩擦磨损试验所用载荷较小,涂层结合强度对其摩擦磨损行为的影响可以忽略,因而有关涂层结合强度的研究不在本文中给出。

  • 采用Rtec公司MFT-5000型多功能摩擦磨损试验机测试涂层的滑动摩擦磨损性能,载荷从低到高分别设定为5N、10N、15N和20N,滑动时间为20min,滑动半径为4mm,滑动速率为0.168m/s。对磨球为直径5mm的ZrO2球。图3所示为球-盘滑动摩擦磨损测试示意图。试样绕着中心轴线转动,对磨球相对静止。磨损试验机利用电脑进行控制。利用激光共聚焦显微镜测试涂层磨痕截面积,计算得到磨损体积。利用磨损体积与载荷和滑动行程的比值计算比磨损率。每种涂层在每种载荷条件下至少测试3个试样,最终的磨损率是3次测试的平均值。采用扫描电子显微镜观察涂层磨痕形貌,分析涂层的磨损机制。

  • 图3 涂层滑动磨损测试示意图

  • Fig.3 Schematic diagram of wear test

  • 2 结果与讨论

  • 2.1 涂层形貌和物相组成

  • 图4 显示了各种不同涂层的表面形貌。在喷涂过程中,粉体颗粒在等离子焰流作用下发生融化,熔融的颗粒在目标基体表面铺展,凝固形成片层状的颗粒,片层相互搭接形成涂层。涂层表面是凹凸不平的,这主要是由片层无规则搭接导致的。涂层表面的小颗粒是熔融颗粒在沉积过程中发生飞溅造成的。此外,在涂层表面存在较为明显的微裂纹,这是沉积涂层过程中形成的热应力造成的[20]。在涂层表面,尤其是片层搭接的地方,存在较多的孔洞。涂层表面孔洞的形成主要是由粉体颗粒的不完全熔融和铺展导致的。另外,在片层内存在孔隙,这主要是由吸附气体的溢出导致的。在Al2O3 涂层表面的片层内存在较多的孔隙(图4a)。但是,在Al2O3-Cr2O3 复合涂层表面片层内的孔隙明显较少,说明Cr2O3 对涂层孔隙有明显的影响。具有较高比重的Cr2O3在Al2O3中固溶,提高了涂层的体密度,最终提高了涂层的致密性[21]。此外,在涂层表面未观察到明显的未熔颗粒。

  • 图4 不同涂层表面形貌

  • Fig.4 Morphology of the coatings

  • 表3 中给出不同涂层的表面粗糙度。Al2O3 涂层的表面粗糙度低于Al2O3-Cr2O3 复合涂层的表面粗糙度。复合涂层的表面粗糙度均在误差范围内,即Cr2O3 对复合涂层表面粗糙度没有影响。涂层的表面粗糙度会影响到涂层的摩擦行为。

  • 表3 各种涂层的表面粗糙度

  • Table3 Surface roughness of the coatings

  • 图5 所示是Cr2O3 含量不同的Al2O3-Cr2O3 复合涂层的XRD图。Al2O3 涂层主要是由 α-Al2O3 相和 γ-Al2O3 相组成。Al2O3-Cr2O3 复合涂层主要是由 α-Al2O3 相、γ-Al2O3 相和Cr2O3 相组成。 α-Al2O3 相的最强衍射峰属于(104)晶面,γ-Al2O3 相的最强衍射峰属于(400)晶面。α-Al2O3 相(202) 晶面的衍射峰与 γ-Al2O3 相(400)晶面的衍射峰接近,但是前者强度非常弱。因此,可以利用 α-Al2O3 相(104)晶面衍射峰的相对强度和 γ-Al2O3 相(400)晶面衍射峰的相对强度近似分析 α-Al2O3 相含量的变化[7]。Al2O3 涂层中 α-Al2O3 相和 γ-Al2O3 相的相对含量比为37%,Al2O3-Cr2O3 复合涂层中 α-Al2O3 相和 γ-Al2O3 相的相对含量比分别为59%、47%和43%,均明显高于37%,说明Cr2O3 可以起到稳定 α-Al2O3 相的作用,这与YANG等的研究结果是一致的[16]

  • 图5 不同涂层的XRD图

  • Fig.5 XRD patterns of the coatings

  • Cr2O3与 α-Al2O3 可以完全相互固溶,晶体结构不发生改变,这是Cr2O3 稳定 α-Al2O3 相的重要机制[22]。喷涂过程中,Al2O3 和Cr2O3熔滴凝固形成的片层彼此搭接,在两者的界面会发生扩散形成Al2-xCrxO3 固溶体相[23]。此外,在Al2O3和Cr2O3的界面存在一定的取向关系,α-Al2O3可以在Cr2O3上凝固形核[24]。由于固溶体的晶体结构和 α-Al2O3 的晶体结构相同,因而其衍射峰位与 α-Al2O3 的衍射峰位很难区分。等离子喷涂过程中熔滴颗粒具有高的冷却速度,元素的扩散速度和时间有限,因而形成固溶体的量是有限的。通过XRD标准卡片和测得的衍射峰强度的对比,推测可能形成的固溶体是Al1.98Cr0.02O3固溶体。

  • 2.2 涂层的力学性能

  • 图6 给出Cr2O3 含量不同的涂层的截面显微硬度。明显地,Cr2O3 的加入提高了涂层的硬度。Al2O3 涂层的硬度为927.3±80.1HV300。随着Cr2O3 含量的增大,涂层的硬度梯度增大。这主要是因为Cr2O3 的硬度高于Al2O3。Cr2O3含量为40%时,复合涂层的硬度与Al2O3 涂层相比提高48%。

  • 图6 不同涂层的显微硬度

  • Fig.6 Micro-hardness of the coatings

  • 当Cr2O3 含量低于40%时,复合涂层的断裂韧性随着Cr2O3 含量的升高而降低[11]。利用压痕法计算得到Al2O3 涂层和Al2O3-40%Cr2O3 复合涂层的断裂韧性分别为2.2±0.4MPa · m 0.5 和4.5MPa·m 0.5,后者的断裂韧性是前者的2倍多。这与YANG等[11]的研究结果是一致的。Cr2O3 含量较低时(<10mol%),由于加热收缩效应, Al2O3-Cr2O3 复合材料的致密性有可能降低[21]。这有可能降低涂层的性能。图7进一步给出Al2O3 涂层和Al2O3-40%Cr2O3 涂层的压痕形貌。Al2O3 涂层压痕对角线上的裂纹长度明显长于复合涂层压痕对角线上的裂纹长度。因此,在相同载荷条件下,复合涂层具有更高的抗裂纹扩展能力。试验发现,当Cr2O3 含量为30%时,在300g载荷作用下,压痕产生的裂纹长度明显长于Al2O3 涂层上压痕产生的裂纹长度,说明涂层抗裂纹扩展的能力较弱。

  • Cr2O3 含量对复合涂层硬度和断裂韧性的影响进一步会导致涂层摩擦学性能的改变。

  • 图7 涂层的压痕形貌

  • Fig.7 Morphology of the indentations in the coatings

  • 2.3 滑动磨损试验结果

  • 图8 所示是涂层在不同载荷条件下的摩擦因数随着滑动时间的变化曲线。摩擦因数曲线包括磨合期和稳定期。在磨合期,涂层与对磨球之间的滑动摩擦因数快速增大;在稳定期,涂层摩擦因数较为平稳。当载荷为5N时,涂层摩擦因数的波动幅度较小。当载荷增大时,涂层摩擦因数的波动较大,尤其是当Cr2O3 含量为40%时,摩擦因数曲线有明显起伏。涂层摩擦因数曲线上的波动除了与设备振动有关外,摩擦副接触表面上微观结构的变化同样会导致其摩擦因数的起伏[25]。随着Cr2O3 含量的增大,复合涂层表面的微观不均匀性增加,导致摩擦因数明显波动。一般地,低的涂层表面粗糙度会导致低的摩擦因数[26]。从图8可以发现,尽管Al2O3 涂层的表面粗糙度较低,但是Al2O3 涂层的摩擦因数偏大。这主要是因为涂层起始表面粗糙度主要影响磨合期的摩擦因数变化。当摩擦进入稳定期时,涂层的表面粗糙度由于磨损的原因会发生明显的变化。

  • 图8 涂层在不同载荷下的摩擦因数曲线

  • Fig.8 Friction factor curve of the coatings with respect to sliding time at different normal loads

  • 涂层磨合期摩擦因数的平均值如图9所示。 Cr2O3 含量和载荷对涂层的平均摩擦因数有明显的影响。Al2O3 涂层、Al2O3-30%Cr2O3 复合涂层和Al2O3-40%Cr2O3复合涂层的平均摩擦因数随着载荷的增大先减小后增大。Al2O3-20%Cr2O3 复合涂层的平均摩擦因数随着载荷的增大梯度降低。

  • 图9 不同涂层的平均摩擦因数

  • Fig.9 Mean-value of the steady friction factor of the coatings

  • 在载荷为5N、10N和15N时,Al2O3-40%Cr2O3 复合涂层的平均摩擦因数最小;在载荷为20N时, Al2O3-20%Cr2O3 复合涂层的平均摩擦因数最小。载荷为5N和10N时,Al2O3 涂层的平均摩擦因数最大;载荷为15N和20N时,Al2O3-30%Cr2O3 涂层的平均摩擦因数最大。总的来说,加入Cr2O3 可以明显降低涂层的摩擦因数,但是Cr2O3对涂层摩擦因数的影响与载荷及其含量是相关的。当载荷较低时,高的Cr2O3含量有利于摩擦因数的降低;当载荷较高时,较低含量的Cr2O3有利于摩擦因数的降低。

  • 图10 显示了涂层磨损率随着载荷的变化趋势。载荷为5N、10N、15N和20N时,Al2O3 涂层的磨损率分别为 (6.8±0.8)×10−4 mm 3/(N · m)、 (9.5±0.9)×10−4 mm 3/(N·m)、(5.7±0.8)×10−4 mm 3/(N·m)和(2.8±0.2)×10−4 mm 3/(N·m)。当载荷低于15N时,相同载荷条件下,Al2O3-40%Cr2O3 复合涂层的磨损率与Al2O3 涂层相比分别降低60%、85%、 79%和21%,耐磨性最好。但是,当载荷为20N时, Al2O3-20%Cr2O3 复合涂层的磨损率与Al2O3 涂层相比降低了50%,耐磨性最好。明显地,Cr2O3 提高了Al2O3 涂层在较高载荷条件下的耐磨损性能。但是,在不同载荷条件下,复合涂层的耐磨损性能具有明显差异。复合涂层中,Al2O3-30%Cr2O3 涂层的磨损率相对较高,耐磨性最差。

  • 图10 不同涂层的磨损率随着载荷的变化

  • Fig.10 Wear rate of the coatings at different normal loads

  • 在Cr2O3 含量一定时,涂层磨损率随着载荷增大有不同的变化趋势。对于Al2O3 涂层来说,随着载荷的增大,磨损率先增大后减小;对于Al2O3-20%Cr2O3 复合涂层来说,随着载荷的增大,磨损率降低; 对于Al2O3-30%Cr2O3 复合涂层来说,磨损率波动不大;对于Al2O3-40%Cr2O3复合涂层来说,磨损率随着载荷的增大而降低,但是当载荷为20N,磨损率略有升高。通过对图9和图10的分析可以得出:与高硬度的氧化锆对磨,涂层摩擦因数和磨损率随着载荷的变化是一致的,高的摩擦因数意味着高的磨损率。

  • 图11 所示是Al2O3-20%Cr2O3 和Al2O3-30%Cr2O3 复合涂层在载荷为10N条件下的磨痕形貌。涂层磨痕表面是凹凸不平的,存在微观断裂区和较完整片层区。涂层的主要磨损机制是微观脆性断裂,在片层边缘可以观察到明显的微观断裂痕迹。在磨痕凹坑区域可以观察到断裂的由片层形成的磨屑。 Al2O3-30%Cr2O3 复合涂层的磨痕明显比Al2O3-20%Cr2O3 复合涂层的磨痕宽,进一步说明前者的磨损量较大,这与磨损体积的检测结果是一致的。

  • 涂层的主要磨损机制是相同的,其磨损率随着载荷的变化是由其微观结构和力学性能决定的。 Cr2O3 提高了涂层的硬度和致密性,减少了裂纹萌生源,使得复合涂层具有相对较高的耐磨损性能。对于Al2O3-40%Cr2O3 复合涂层来说,其优异的耐磨性主要归因于其高的硬度和断裂韧性。对于Al2O3-20%Cr2O3 涂层来说,其优异的耐磨性能主要归因于涂层的高硬度和高致密性。复合涂层中,当Cr2O3 含量为30%时,尽管涂层较为致密,但是涂层的耐磨性较差,这主要归因于涂层低的断裂韧性和强度[11]。此外,涂层中较高含量的亚稳Al2O3 相也不利于其耐磨性的提高。Cr2O3提高了涂层在较高载荷状态下的耐磨损性能。但是,当Cr2O3 含量为20%时,复合涂层在20N条件下的耐磨损性能是最优的。首先,较高含量的 α-Al2O3 有利于其耐磨性的提高。其次,这还可能是由Al2O3 和Cr2O3 自身的热传导系数差异引起的[27]。涂层在摩擦过程中会产生大量的热量,导致局部温度升高。Al2O3 的热传导系数高于Cr2O3,Al2O3-20%Cr2O3 复合涂层更利于摩擦热的传导,抑制了局部温度升高导致的相变。因而,在高载荷条件下,其具有更好的耐磨损性能。

  • 图11 涂层在载荷为10N时的磨痕形貌

  • Fig.11 Wear track of the coatings sliding at normal load of 10N

  • 3 结论

  • 重点研究Cr2O3含量和载荷对Al2O3-Cr2O3复合涂层与高硬度ZrO2 陶瓷球对磨时的摩擦磨损行为, 得到如下主要结论:

  • (1)Al2O3-Cr2O3 复合涂层的摩擦因数和耐磨损性能与磨损条件和Cr2O3 含量是相关的。载荷较低时,较高含量的Cr2O3 可以降低涂层的摩擦因数,提高其耐磨性;载荷较高时,较低含量的Cr2O3 可以降低涂层的摩擦因数,提高其耐磨性。

  • (2)Al2O3-Cr2O3 复合涂层高的耐磨性主要归因于其高的硬度和断裂韧性。较低含量的亚稳Al2O3 相和高的导热系数同样有利于复合涂层耐磨性的改善。

  • (3)Al2O3 涂层及Al2O3-Cr2O3 复合涂层与高硬度陶瓷球对磨时的主要磨损机制是微观脆性断裂。 Cr2O3 对复合涂层的磨损机制没有明显影响。

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