磁控溅射论文：磁控溅射 硬质涂层 高温磨损 热疲劳.doc

【关键词】磁控溅射 硬质涂层 高温磨损 热疲劳【英文关键词】magnetron sputter hard coating high temperature wear thermal fatigue磁控溅射论文：非平衡磁控溅射离子镀沉积Cr-Me-N涂层高温承载能力研究【中文摘要】采用物理气相沉积(PVD)技术在基体表面涂覆抗高温、耐磨的硬质涂层,可以提高材料表面性能。CrN硬质涂层具有硬度高,耐磨、耐腐蚀性等特点,在铸造、机械加工及成型等领域得到较广泛的应用。但是,由于CrN薄膜抗氧化温度较低,高温使用性能差,限制了其在高温领域的应用。添加其他合金元素形成多元合金硬质涂层可有效提高薄膜的高温使用性能,尤其对提高模具的使用寿命有重要意义。本研究在CrN薄膜中加入A1和Nb元素并对其合金化,应用闭合场非平衡磁控溅射离子镀沉积技术,在M42高速钢和H13热作模具钢基体上制备具有优异结合强度的CrAlN和CrAlNbN两种多组元硬质梯度薄膜。利用XRD、GDS、EDX、SEM、光学显微镜等检测方法,分析研究薄膜的相组成、成分分布、表面及截面形貌。通过高温球盘磨损实验机、显微硬度计、洛氏硬度计及球坑仪等仪器考察了镀膜试样的摩擦系数、比磨损率、膜基结合强度等力学性能,深入研究CrAlNbN和CrAlN薄膜的高温摩擦学行为,阐述了不同阶段摩擦系数变化规律及薄膜的高温磨损机理。并通过观察镀膜试样在模拟真实压铸模具工作条件下表面裂纹形貌,分析了不同循热环次数后镀膜的热疲劳性能以及Nb元素对薄膜抗热疲劳性能的影响。得出主要结论如下：1.选取Al及Nb作为添加合金元素,利用磁控溅射制备CrAlNbN和CrAlN薄膜并进行工艺参数优化。在Al、Nb靶电流为2A工艺下制备的薄膜成分梯度分布,膜基结合强度最好,表面光滑,致密性好,缺陷较少。薄膜呈柱状晶生长,晶柱间间距很小。CrAlN薄膜相组成主要包括CrN和AlN；加入Nb元素后,生成了NbN化合物相。2.高温磨损时摩擦系数在摩擦开始阶段较大,随后逐渐降低。与CrAlN薄膜相比,CrAlNbN薄膜的摩擦系数相对较高,但磨损量较少,比磨损率降低。CrAlNbN薄膜中NbN化合物的弥散析出和固溶强化,不仅改善基体断裂韧性,降低摩擦过程中镀层的断裂或剥落倾向,是提高其耐磨性的主要原因。CrAlN和CrAlNbN薄膜的磨损机理分别以磨粒磨损和黏着及氧化磨损为主。3. CrN、CrAlN和CrAlNbN镀膜试样的抗热疲劳性能相对基体均有所提高。其中,镀CrAlNbN薄膜的试样表面出现的裂纹长度短、数量少,其抗热疲劳性能优于CrN和CrAlN薄膜。CrAlNbN薄膜中高硬NbN化合物可提高薄膜的表面强度,抑制热疲劳裂纹的萌生。此外,高温形成的Nb2O5氧化物高温稳定性好,可改善模具表面的抗腐蚀性能,有助于提高薄膜的热疲劳抗力。【英文摘要】Hard coatings deposited by PVD have been used to enhance the ability of high temperature wear-resistant. Chromium nitride is one of the most commonly used coating materials for casting, machining and forming applications because of its high hardness, excellent wear and corrosion resistances. To improve its poor oxidation resistance and tribological performance in high temperature, ternary compounds including other metals such as Al, V, Nb have been explored to prolong the life of die casting tools. In this paper, Al and Nb are added to CrN coatings to form alloy coatings. The different tribological properties of CrAlNbN and CrAIN coatings at high temperature, the details of friction character and mechanism of wear resistant of coatings at various sliding friction stages have been studied. Thermal fatigue property of H13specimens deposited different coatings was tested using the thermal fatigue test machine and crack morphology was observed by optical microscope. The influence of Nb in promoting the thermal bearing capacity has been studied. With the technology of closed field unbalanced magnetron sputter system (CFUBMS), CrAlN and CrAlNbN hard coating were deposited on the surface of the M42HSS and H13steel. The surface and cross-section morphology, the adhesion between the substrate and the coating, phase structure as well as the morphologies for coatings and the worn surfaces was evaluated using the Rockwell indentation, EDX, SEM, GDS and XRD, respectively. A series of pin-on-disc experiments sliding against a WC/Co counterpart ball, were carried out at high temperature(550). Effect of alloy elements Nb adding to the CrAlN film showed that:1. Chosen aluminum and niobium as the target materials, CrAlN and CrAlNbN films are prepared using CFUBMS. The coatings deposited at the optimized parameter (target current of2A) is smooth, compact and less defects, exhibiting the gradient composition distribution and the strongly bonding to the substrate. The film grows as columnar crystal with a narrow spacing. The CrAlN coating is composed of CrN and AlN. The CrAlNbN coating contains NbN in addition to CrN and AlN.2. The friction coefficient for high temperature wear increases at initial stage and then decreases gradually. Compared to CrAlN coatings, the CrAlNbN coatings maintain a larger value of friction coefficient, but a lower values for both wear volume and specific wear rate. The fracture toughness of substrates, spalling or fracture of coatings are improved by solution strengthening of NbN precipitate, resulting in a high wear resisitance. The wear mechanism is abrasive for CrAIN coatings and adhesive and oxidation wear for CrAlNbN coatings3. The thermal fatigue properties of H13specimens deposited CrN, CrAIN, CrAlNbN coatings are improved obviously as compared to H13substrates. The thermal fatigue resistance of CrAlNbN coatings is the best because the density and length of cracks on the surface of CrAlNbN coatings is less than those of CrN and CrAIN coatings. It is attributed to the harder compound of NbN which can increase the surface strength of CrAlNbN coatings and restraine the initiation of thermal fatigue cracks. In addition, the oxide of Mb2O5with high temperature stability leads to the improvement of corrosion resistance and is also beneficial to increase thermal fatigue resistance.【目录】非平衡磁控溅射离子镀沉积Cr-Me-N涂层高温承载能力研究摘要3-5ABSTRACT5-7目录8-11第一章 绪论11-231.1 引言111.2 常用压铸模具钢及其性能11-131.2.1 H13钢的性能121.2.2 热作模具钢基本失效形式12-131.3 提高模具寿命途径13-151.3.1 氮化处理技术141.3.2 表面涂覆技术14-151.4 闭合场非平衡磁控溅射离子镀技术15-181.4.1 基本原理及发展15-181.4.2 技术优缺点181.5 研究课题的提出18-201.5.1 研究目的和意义18-191.5.2 研究内容19-20参考文献20-23第二章 实验设备及方法23-312.1 实验材料232.2 实验材料准备23-242.3 实验设备242.4 制备方法及工艺24-262.5 检测方法26-312.5.1 显微硬度的检测262.5.2 涂层厚度的计算26-272.5.3 膜基结合强度的测定272.5.4 涂层形貌、微观结构及成分的检测27-282.5.5 涂层磨损性能的测试282.5.6 热疲劳性能的测试28-31第三章 Nb元素对Cr-N基薄膜的微观结构及基本力学性能的影响31-433.1 前言31-323.2 实验方法32-333.3 实验结果及分析33-393.3.1 不同Al或Nb含量的薄膜厚度变化333.3.2 薄膜厚度和结合强度变化33-353.3.3 薄膜相结构35-363.3.4 不同Al或Nb含量的薄膜形貌36-393.4 结论39-41参考文献41-43第四章 添加Nb元素对Cr-N系多元合金薄膜高温摩擦性能的影响研究43-614.1 引言434.2 磨损机理43-464.2.1 不同类型的磨损机理43-454.2.1.1 磨粒磨损43-444.2.1.2 黏着磨损444.2.1.3 腐蚀磨损444.2.1.4 疲劳磨损44-454.2.2 耐磨性的影响因素454.2.3 如何提高材料的耐磨性45-464.3 实验方法464.4 实验结果及分析46-584.4.1 比磨损率46-474.4.2 摩擦系数47-494.4.3 显微硬度49-504.4.4 成分变化50-514.4.5 磨损区域形貌51-584.4.5.1 对磨球形貌51-534.4.5.2 轨道形