稀土元素钇对Laves相NbCr_2合金在1100℃氧化行为的影响

采用机械合金化及热压烧结工艺制备了掺杂0.07%～1.35%(质量分数)稀土元素钇的Laves相NbCrz合金,研究了钇含量对NbCrz合金在1 100℃氧化行为的影响,并探讨了其作用机制.结果表明:只有添加适量的钇(0.07%～0.14%)才能降低NbCr2合金的氧化速率,提高NbCr2合金的抗氧化性能;NbCr2合金高温抗氧化性能的提高,主要是由于稀土元素钇增强了氧化膜与基体的结合性能.     

激光熔覆原位自生Ti-Al-Si复合涂层的微观组织和高温抗氧化性能

为提高钛合金的高温抗氧化性能,采用激光熔覆原位自生技术,在TC4钛合金表面自行设计并制备了原子百分比为Ti∶Al∶Si=41∶41∶18和Ti∶Al∶Si=35∶35∶30的两种涂层。通过XRD、OM、SEM表征了涂层的微观组织和物相组成;借助管式电阻炉测试了涂层和基体试样在800℃×24h×5次循环氧化条件下的高温抗氧化性能;结合氧化增重和氧化动力学曲线分析了涂层的高温抗氧化机理。结果表明,涂层主要由Ti5Si3、Ti7Al5Si12、Ti3Al、TiAl和TiAl3等物相组成。涂层中没有出现一般激光熔覆所产生的外延生长柱状晶组织,全部为细小等轴晶。在800℃×24h×5次循环氧化条件下,TC4基材单位面积的氧化增重约为35.1mg·cm-2,涂层的约为2.8mg·cm-2和3.3mg·cm-2。两种涂层的高温抗氧化性能较钛合金基材分别提高了12.5倍和10.6倍。激光熔覆原位自生Ti-Al-Si复合涂层能明显改善TC4钛合金的高温抗氧化性能。涂层抗氧化性改善的机理,一方面是表面生成了连续致密的TiO2、Al2O3、SiO2氧化层,阻碍了氧扩散;另一方面是提高了氧化层的黏附性,使氧化层不易从涂层表面剥落,对涂层未氧化部分起到了很好的保护作用。     

热处理条件下激光原位合成高铌Ti-Al金属间化合物复合涂层的微结构特征

为了提高钛合金的高温抗氧化性能,推动钛合金在高温和复杂工况环境下的进一步工程应用,利用高能激光束作用下Ti、Al、Nb三种元素混合粉末之间的原位反应在BT3-1钛合金表面制备了高温抗氧化的高铌Ti-Al金属间化合物复合涂层。针对原位反应所制备涂层存在的缺陷,通过自行设计的热处理工艺优化了涂层和界面微观组织。借助光学显微镜(OM)、X射线衍射仪(XRD)、扫描电镜(SEM)分析了热处理前后复合涂层的物相结构及显微形貌。结果表明:热处理前的涂层主要由单质Nb、金属间化合物γ-TiAl、α_2-Ti_3Al、Ti_3Al_2等物相组成;热处理后的复合涂层,单质Nb固溶到γ-TiAl和α_2-Ti_3Al中,同时形成了新相Ti_3AlNb_(0.3),涂层近似为γ-TiAl+α_2-Ti_3Al双相层片状等轴晶组织。此外,涂层中并未观察到减弱抗氧化性的单质Nb颗粒和Ti_3Al_2相,Ti、Al、Nb的宏观偏析得以消除,涂层与基材界面位置的气孔和裂纹均以消失,出现了明显的白亮带冶金结合过渡层,涂层组织也更加均匀致密。热处理对提高钛合金表面Nb的合金化程度和改善Ti-Al金属间化合物的高温抗氧化性能起到了显著的促进作用。     

电厂锅炉水冷壁管高温抗氧化涂层的制备及性能研究

电厂锅炉水冷壁的高温氧化问题严重地影响了电厂的安全性和经济性，为了解决该问题，文中采用热化学反应法制备了适用于锅炉水冷壁管的陶瓷涂层，以高温抗氧化性为主要指标，对涂层的各项性能进行评价。结果表明：在800℃温度下，涂层单位面积氧化增重为0.83 mg/cm²，涂层结合力为54.6 N，可经受18次循环空冷。制备的陶瓷涂层的氧化增重曲线符合抛物线型，氧化活化能为175.82 k J/mol，抗氧化性能良好，有效地降低了电厂锅炉水冷壁的高温氧化速率，延长了其使用寿命。     

不锈钢表面ZrO2涂层的制备及其性能

用电沉积法，经热处理在不锈钢表面制备了ZrO2陶瓷涂层。研究了不同前处理工艺对ZrO2陶瓷涂层的影响，FTIR、SEM等分析结果表明：ZrO2涂层致密均匀，锆元素和氧元素在微区分布均匀。采用差重法、浸泡试验和阳极极化曲线测试了涂层在1000℃的抗高温氧化性和在硫酸介质中的耐蚀性，结果表明ZrO2陶瓷涂层提高了不锈钢的高温抗氧化性和耐蚀性能。     

TiN涂层提高耐热合金高温抗氧化性试验

ＴｉＮ涂层提高耐热合金高温抗氧化性试验章跃（淮阴工业专科学校邮编２２３００１）王介淦（南京航空航天大学邮编２１００１６）关键词ＴｉＮ涂层，耐热合金，高温，抗氧化性一、引言科学技术的发展对工程材料的要求在不断提高，航空、航天、核能等尖端技术的飞速发展迫...     

铌及其合金高温抗氧化涂层研究

主要介绍了铌及其合金的氧化机理和铌合金高温表面涂层保护的3方面技术—抗氧化金属与合金涂层、金属间化合物涂层、复合防护涂层以及目前存在的主要问题,并简要的提出了高温抗氧化涂层的发展方向。     

激光熔敷陶瓷涂层的抗氧化性

研究激光熔敷陶瓷（ＺｒＯ２－Ｙ２Ｏ３）涂层在高温下的抗氧化性，通过金相、ＳＥＭ、ＴＥＭ、ＥＤＡＸ和Ｘ线衍射等测试方法，对涂层在激光熔敷前后的形貌、结构、组织进行分析，并比较高温下的抗氧化性，讨论涂层在高温下对其体保护的机理。     

PCVD直流脉冲沉积温度对TiN／TiSiN复合涂层高温氧化性能的影响

采用工业用直流脉冲等离子体增强化学气相沉积（PCVD）法在硬质合金刀具材料上制备了TiN／TiSiN复合涂层。对比研究了TiN及不同温度制备的TiN／TiSiN复合涂层高温抗氧化性能。研究表明：含有非晶阻隔抗氧化结构si3N。的TiN／TiSiN复合涂层高温氧化性能远高于TiN涂层,TiN／TiSiN复合涂层提高到800℃,仍可避免出现较大面积氧化及脱落;PCVD直流脉冲沉积制备温度对涂层高温抗氧化能力有重要影响,550℃沉积制备的致密、均匀、颗粒小的复合涂层高温氧化性能最佳,600℃次之,500％最差。     

TiAl合金表面NiCrAlY涂层的抗高温氧化性能

采用多弧离子镀技术在γ-TiAl合金表面制备了NiCrAlY涂层,用SEM、EDS和XRD等分析了涂层在高温氧化前后的形貌、结构和物相组成,用恒温氧化方法测试了涂层与基体的氧化动力学曲线。结果表明:涂层在高温下可形成保护性氧化膜,使其抗氧化性能显著提升;在650~950℃氧化时,镍和钛元素发生互扩散,850℃时,涂层与基体之间形成了扩散带和齿状TiNi相,950℃时,互扩散现象加剧,涂层表面生成了TiO2,涂层氯化膜与基体间形成了Kirkendall孔洞,对其抗高温氧化性能不利。     

Electroless deposition and structure of Ni-MoSi2 composite coatings

Nickel-molybdenum silicide (Ni-MoSi₂) composite coatings were produced by a technique using an electroless nickel bath containing MoSi₂ in suspension. The operating conditions of the electroless deposition of Ni-MoSi₂ composite coatings and their structure were studied by X-ray fluorescence and X-ray diffraction. The mechanical properties of the composite coatings were determined. Some properties of the Ni-MoSi₂ composite coatings, such as oxidation resistance at high temperature, were investigated. These materials have potential for use in high-temperature applications involving oxidation resistance.     

TiAl合金表面等离子喷涂双层涂层组织与性能的研究

用等离子喷涂法在TiAl合金基体表面喷涂得到由CoNiCrAlY粘结层和ZrO2 Y2O2陶瓷外层组成的双层结构的热障涂层，进行了高温氧化试验并用SEM和光学显微镜观察分析了涂层的组织及形貌。结果表明：粘结层厚度为60μm，陶瓷外层厚度为250μm。喷涂后试样高温抗氧化能力提高。     

TiVN涂层的耐磨性与切削性能的关联研究

通过多弧离子镀沉积技术制备了TiN和TiVN涂层,对比了两种涂层在不同工况下的摩擦磨损性能和切削性能,并指出影响刀具涂层服役性能的主要因素。结果表明,V元素掺杂有效提高了TiN涂层的硬度和结合力、减小了TiN涂层的摩擦因数和低温下的磨损率,但V容易氧化的特性导致500 ℃及以上温度TiVN涂层产生较高的磨损率。切削测试表明,在麻花钻的主切削刃和横刃区域两种涂层发生明显的剥落,而在后刀面涂层未发生明显剥落,TiVN涂层较高的膜基结合强度和耐磨性能使得它对刀具的防护效果更佳;刀具涂层的服役性能与其耐磨性能和膜基结合强度有关,刀具的主切削刃和横刃区域对涂层的耐磨性能和膜基结合强度有着苛刻的要求,且切削刃尖端温度较高,对涂层的高温耐磨性能和膜基结合强度要求也高。     

Effects of carbon content on the high temperature friction and wear of chromium carbonitride coatings

Chromium nitride-based coatings are often used in application at high temperature. They possess high wear and oxidation resistance; however, the friction coefficient is typically very high. Therefore, we doped CrN coatings by carbon with the aim to improve tribological properties at elevated temperature, particularly to lower the friction. CrCN coatings were prepared by cathode arc evaporation technology using constant N₂ flow and variable C₂H₂ flow. The coatings with a thickness of 3-4 μm were deposited on hardened steel substrates and high-temperature resistant alloy. The carbon content varied from 0 at.% (i.e. CrN) up to 31 at.%. The standard coating characterization included the nano-hardness, adhesion, chemical composition and structure (including hot X-ray diffraction). Wear testing was done using a high temperature tribometer (pin-on-disc); the maximum testing temperature was 700 °C. The coatings with carbon content 12-31 at.% showed almost identical tribological behaviour up to 700 °C.     

Investigation on MoS2 and graphite coatings and their effects on the tribological properties of the radial spherical plain bearings

With constant enlargement of the application areas of the spherical plain bearings, higher quality lubrication of the bearings is required. To solve the lubricating problems of spherical plain bearings under high temperature, high vacuum, high speed, heavy loads and strong oxidation conditions, it is urgent for us to develop more excellent self-lubricating technologies. In this paper, the bonded solid lubricant coatings, which use inorganic phosphate as the binder, the mixture of MoS2 and graphite with two different weight proportions as the solid lubricant, are prepared by spraying under three different spray gun pressures. The bonding strength tests on the coatings show that the best spraying pressure is 0.2 MPa and the better mixing proportion of MoS2 to Graphite is 3:1. Then for the radial spherical plain bearings with steel/steel friction pair, after the coatings are made on the inner ring outer surfaces, the friction coefficient, the wear loss and the friction temperature of the bearings under four oscillating frequencies are investigated by a self-made tribo-tester. The test results, SEM of the worn morphologies and EDS of worn areas show that tribological properties of the bearing are obviously improved by the bonded solid lubricant coatings. When sprayed under the spray gun pressure of 0.2 MPa, the bearings have better anti-friction and anti-wear properties than those sprayed under 0.1 MPa and 0.3 MPa. Further as proved from the XPS analysis, between the coating with 3:1 mixing ratio of MoS2 to Graphite and the coating with 1:1 ratio, the former has less oxidation occurred on the surface and therefore has better tribological characteristics than the latter. This paper provides a reference to developing a new product of the radial spherical plain bearings with high bonding strength, oxidation resistance and abrasion resistance.     

Comparison in erosion behavior of iron-base coatings sprayed by three different arc-spray processes

The elevated temperature erosion behavior of three iron-base coatings sprayed by high velocity continuous combustion (HVCC) process was determined in a laboratory elevated temperature erosion tester and compared with the behavior of coatings sprayed using combustion arc-spray and standard arc-spray processes. Test conditions attempted to simulate erosion conditions found at the heat exchanger tubes in the coal-fired boilers. Two bed ashes A (highly erosive) and B (medium erosive bed ash) retrieved from two operating boilers were used as erodent materials. In addition, some other properties, such as microhardness, porosity, and oxidation rate, of coatings were also measured and compared.

Erosion test results indicated that the three iron-base coatings sprayed with HVCC process demonstrated higher erosion resistance than the ones sprayed with the other two arc-spray processes, when eroded by bed ash B. When eroded by high erosive ash (bed ash A), the three arc-sprayed iron-base coatings exhibited similar levels of erosion resistance, the ones sprayed with HVCC process being slightly better than those sprayed with the other two processes. The difference of erosion behavior between sprayed coatings produced by different processes closely correlated with their microstructure and the characteristics of ash materials rather than the microhardness of coatings. The erosion mechanism of coatings was also discussed and compared.     

ZrO2热障涂层耐高温冲刷性能研究

采用等离子喷涂工艺制备了NiCoCrAlY／ZrO2热障涂层，利用超音速火焰喷涂（HVOF）ZrO2粒子高速冲刷涂层表面，考察ZrO2热障涂层的耐高温冲刷性能。结果表明，等离子喷涂NiCoCrAlY／ZrO2热障涂层具有较好的耐高温冲刷性能，经高温高速粒子冲刷20s后，涂层与基体结合良好，涂层完整，未出现大面积的剥落。等离子喷涂ZrO2热障涂层高温冲刷的主要磨损机理为脉动冲击作用造成的裂纹扩展、涂层颗粒变形磨损和微切削。涂层的耐高温冲刷性能主要取决于涂层的硬度。     

Corrosion and wear behaviour of ZrN thin films

Abstract

ZrN coating is an alternative candidate to replace the conventional TiN coating especially for high temperature oxidation resistance applications. ZrN coatings of varying thickness (1·5, 2·0, 2·5, 3·0 and 4·0 μm) were deposited on 316 stainless steel substrates by cathodic arc evaporation in a reactive nitrogen atmosphere. The influences of lamellae thickness on the microstructure, tribological and corrosive properties of the films were investigated. The coefficient of steady state friction of the films ranged from 0·213 to 0·659. The corrosion resistance of the coatings was tested in 1 N H₂SO₄ solution. The results indicate that the microstructure, wear and corrosion properties of the films were dependent on lamellae thicknesses and film structure.