环氧树脂基防冻粘涂料的制备及其性能研究

制备了一种基于环氧树脂的防冻粘涂料,通过正交试验,确定了试验影响因素对涂层冻粘强度的影响。最后,通过对试样接触角及其与水之间的剪切冻粘强度进行对比研究发现,随着接触角的增大,冻粘强度逐渐降低,且十七氟癸基三乙氧基硅烷的含量对环氧树脂基防冻粘涂层的疏水性影响不大。     

钢板表面波纹度对煤冻粘强度的影响分析

寒冷地区煤炭运输设备上煤的冻粘问题较为突出且研究较少,针对冻粘基体表面波纹度对煤冻粘强度的影响,选取5种不同表面波纹度的钢板,分别对其上各粒度和外在水含量的煤样进行冻粘强度试验。结果表明:当煤样外在水含量为20%较小时,随着钢板表面波纹度间距参数Wsm从0.70 mm逐渐增至1.81mm,幅度参数Wc从0.081 4 mm逐渐增至0.216 5 mm,粒径dWsm的较小粒度煤样冻粘强度明显增加,粒径dWsm的较大粒度煤样冻粘强度无明显增减趋势,d介于Wsm变化范围间的中等粒度煤样冻粘强度先无明显变化,后逐渐增加;当煤样外在水含量为40%较大时,各粒度煤样随钢板波纹度参数值的增加而小幅减小。实际中为降低煤冻粘强度,当煤外在水含量较小时应减小金属冻粘基体材料表面波纹度参数,而当外在水含量较大时可提高金属基体表面的波纹度参数。     

改向滚筒防冻粘特性的试验研究

针对煤与带式输送机改向滚筒表面的冻粘问题,设计了煤冻粘强度试验装置。模拟改向滚筒表面环境,在温度为-30℃和冷冻时间为3 h的条件下,研究了几种不同材料与含水率30%煤泥的冻粘特性。通过对比试验证明,UHMW-PE材料在法向、切向冻粘强度均比测试的其它材料低,说明了其具备良好的防冻粘能力;根据UHMW-PE包胶滚筒实际应用情况,进一步说明了可以利用UHMW-PE材料作为滚筒的涂层,以达到防冻粘的效果。     

煤冻粘强度与水润滑动摩擦因数的关系

煤炭是我国重要的基础能源,然而我国高寒地区冬季采煤中由于改向滚筒表面冻粘引起的输送带跑偏、撕裂问题严重制约了冬季煤矿的安全和高效生产,给公司带来了巨大的经济损失,现有的解决方法虽然对煤的冻粘有一定缓解但无法从根本上解决问题。通过自行设计的冻粘强度测试装置,在温度为-25℃和冷冻时间为3 h的条件下,测试了4种不同材料与含水率40%煤泥的冻粘特性。实验研究发现,煤的法向与切向冻粘强度均随着材料水润滑动摩擦因数的减小而下降,呈现一定线性关系,结果表明,提高材料水润滑性能可以降低冻粘强度,这一发现对工程领域防冻粘涂层的选择和制备具有重要指导意义,值得进一步深入探索与研究。     

基于仿生学的防冻粘试验研究

为了改善解决寒冷地区冬季运煤过程中改向滚筒、皮带上存在的冻粘问题,在查阅相关冻粘理论的基础上,受仿生学启发,对仿生凸包几何结构在改向滚筒、皮带上的应用进行了理论分析和试验研究。理论上验证了仿生凸包几何结构可变相增大材料表面的水接触角,即可在一定程度上减小冻粘强度;参考已有防冻粘特性试验研究,利用超高分子量聚乙烯(UHMW-PE),设计加工了一块高度为1.0 mm、投射半径为2.4 mm、中心距为6.4 mm的仿生凸包模板和另一块同种材料的光滑模板,通过自制的冻粘强度测试装置,在温度为-25℃和冷冻时间为3 h的条件下,测试了两种模板与含水率40%煤泥的冻粘特性。结果显示:仿生凸包模板的法向冻粘强与切向冻粘强度分别降低了8%、12%左右,即从试验方面验证了仿生几何型凸包的确具有一定的防冻粘性能,希望可以运用于防冻粘领域。     

压力对煤冻粘强度的影响

煤炭是我国重要的基础能源,而煤的冻粘严重制约了冬季煤矿的安全和高效生产。压力作为煤冻结条件的次要因素,对煤的冻粘强度具有重要影响。通过自行设计的冻粘强度测试装置,在温度为-25℃和冷冻时间为3 h的条件下,测试了6种不同材料与含水率40%煤泥的冻粘特性。实验研究表明,通常压力会使煤的冻粘强度增大,如普板(Q235),预压力情况的法向冻粘强度是无压力下的6.2倍,预压力情况的切向冻粘强度是无压力下的5.9倍。然而六种材料中只有聚四氟乙烯(PTFE)的法向和切向冻粘强度在压力条件下均不增反减。某种意义上表明,压力会增大亲水材料的冻粘强度反而会降低疏水材料的冻粘强度。PTFE材料的这种优良特性在高寒地区煤炭运输领域表现了广泛的应用前景,值得进一步深入研究。     

加成型硅胶基防粘涂层性能研究

本文以加成型硅胶基材料为主要成膜物质,通过添加一定量的POSS和纳米SiO_2降低涂层的表面张力,得到具有防粘性能的涂层。研究了涂层的接触角、表面粗糙度和表面防粘性能,得出当POSS质量含量为3%时,接触角为92.9°,表面粗糙度值为25.2nm,此时涂层表面的防粘力达到一个较低值。随着聚氨酯胶带与涂层表面接触时间的延长,涂层表面的防粘力呈逐渐增大的趋势。     

钢板表面粗糙度对煤冻粘强度的影响

煤炭是我国的基础能源和重要原料,在国民经济中占有重要的战略地位,而由煤的冻粘引起的改向滚筒表面粘结、皮带抖动、回程沿线撒煤等问题严重制约了煤炭的冬季运输。文献表明材料表面粗糙度对冻粘具有重要影响,为了通过改善材料表面形态而缓解煤的冻粘问题,课题组自行设计了冻粘强度测试装置,在一定的冷冻条件下,测试了含水率40%的煤泥与6种不同粗糙度钢板的冻粘属性。结果表明,煤的冻粘强度随着粗糙度呈W曲线变化,大约在R_a=9μm~10μm时出现最小值,进一步说明,适当的表面粗糙度可以降低煤的冻粘强度。对于冻粘机理的研究以及其他工程领域的冬季防粘减粘具有指导意义。     

聚四氟乙烯涂层滚筒防冻粘特性的试验研究

为了研究我国冬季露天矿运煤过程中改向滚筒冻结煤泥问题,采用自主设计加工的实验装置,模拟生产现场,研究了不同材料,在不同温度和不同的冷冻时间的条件下冻粘特性的变化情况。结果表明不同材料与干基含水率40%的煤泥之间的冻粘强度不同,其中聚四氟乙烯(PTFE)材料在法向和切向的冻粘强度均比其他材料低,在-25℃,冷冻2.5小时的情况下切向冻粘系数为0.037 MPa,法向冻粘系数为0.076 MPa,是相同情况下的超高分子量聚乙烯(UHMW-PE)材料法向冻粘系数的1/3左右,是其切向冻粘系数的1/6左右;是Q235材料法向冻粘系数的1/44左右,是其切向冻粘系数的1/19左右,说明了PTFE具备良好的防冻粘能力。试验还表明温度对冻粘强度有一定影响,但不呈线性关系;冷冻时间大于3小时后冻粘强度变化比较小;材料的切向冻粘系数通常大于法向冻粘系数;界面冻粘强度与实验添加煤样的多少无关。     

煤粒度对煤炭运输设备冻粘强度影响的试验分析

为分析煤粒度对煤炭运输设备上煤冻粘强度的影响规律及原因,应用研制的冻粘强度测试装置,分别进行六种不同粒度煤样在超高分子量聚乙烯、橡胶和Q235三种典型运输设备材料上的冻粘强度试验。结果表明:随着粒度从d0.1 mm逐渐增大至d2 mm,煤样在三种材料上的冻粘强度普遍降低,煤粒度小,其冻粘界面连续致密,与基体接触面积大,同时基体表面对煤颗粒的吸附作用强,导致冻粘强度大,煤粒度大,冻粘界面有较多空隙缺陷,与基体接触面积小,吸附作用弱,导致冻粘强度小;相同粒度煤样在Q235材料上冻粘强度较大,普遍高于橡胶和超高分子量聚乙烯材料,尤其当粒度很小时(d0.1 mm),煤与Q235材料表面间的冻结强度可能超过冻煤自身冻结强度,分离或清除冻粘煤时易发生冻煤自身的断裂。     

基体表面的分数维对电弧喷涂层结合强度的影响

研究了不同喷砂角度下２０钢基体表面的粗糙度和分数维的变化及其对电弧喷涂层结合强度的影响,结果发现,不同角度喷砂处理对２０钢基体表面的平均粗糙度影响不大,而基体表面的分数维则受喷砂角度的影响。并且存在一个最优喷砂角度,此时基体表面形貌的分数维最大,电弧喷涂层的结合强度值也最大。     

Finite element analysis of coating adhesion failure in pre-existing crack field

Abstract

The influence of a pre-existing crack field on coating adhesion failure in a steel surface coated with a 2 μm thick titanium nitride (TiN) coating was investigated by finite element method modelling and simulation. The stress and strain fields were determined in contact conditions with a spherical diamond tip sliding over the coated surface at a loading of 8 N. One crack in or at the coating increased the maximum tensile stresses with six times from 82 to 540 MPa when the crack was vertical through the coating or L shaped and with nine times when the crack was horizontal at the coating/substrate interface. A simulated multicrack pattern relaxed the tensile stresses compared to single cracks. The results indicate that a cracked coated surface needs to have about five to nine times higher adhesive and cohesive bonds to resist the same loading without crack growth compared to a crack free surface. For optimal coated surface design, the strength of the adhesive bonds between the coating and the substrate in the vertical direction needs to be 50% higher than the cohesive bonds within the coating and the substrate in the horizontal direction. The first crack is prone to start at the top of the coating and grows vertically down to coating/substrate interface, and there it stops due to the bigger cohesion within the steel material. After this, there are two effects influencing that the crack will grow in the lateral direction. One is that steel cohesion is normally bigger than the coating/interface adhesion, and the second is that there are higher tensile stresses in the horizontal than in the vertical cracks. Several vertical cracks can stop the horizontal crack growth due to stress relaxation.     

爆炸喷涂Cr_3C_2/25NiCr涂层抗微动磨损性能的研究

研究爆炸喷涂Cr3C2 2 5NiCr涂层的抗微动磨损性能。结果表明 ,爆炸喷涂Cr3C2 2 5NiCr涂层的层间氧化物含量和孔隙率低 ,组织致密 ,结合强度高 ,涂层的抗接触疲劳性能得到有效改善 ,抗微动磨损能力比K417镍基合金和等离子喷涂层显著提高。     

The influence of surface defects on the mechanical and tribological properties of VN-based arc-evaporated coatings

The influence of surface defects, i.e., droplets and craters, on the mechanical and tribological properties of arc-evaporated V_xN coatings deposited on cemented carbide has been investigated in a scratching contact using a diamond stylus and a sliding contact using a stainless steel pin. Post-test characterisation using 3D optical surface profilometry and scanning electron microscopy was performed in order to investigate the mechanical and tribological response of the coatings. The results show that scratch induced coating cracking mainly is restricted to larger droplets showing a low interfacial bonding to the adjacent coating matrix. The influence of coating defects on the cohesive strength, i.e., the tendency to chipping of small coating fragments, was found to be relatively small. In contrast, the presence of defects may have a significant impact on the interfacial adhesive strength, increasing the tendency to spalling. In sliding contact, surface defects such as droplets and craters have a strong impact on the tribological behaviour of the coatings causing abrasive wear of the less hard counter material surface and material transfer to the coating, both mechanisms affecting the friction characteristics of sliding contact tribo systems.     

电刷镀法制备钢基体超疏水表面的实验研究

采用复合电刷镀技术,在Q235钢表面制备了具有超疏水性能的n-SiO2/Ni纳米复合镀层,在优选的工艺参数下,获得了接触角为1698°、滚动角为23°的超疏水表面。研究了刷镀电压和刷镀时间对镀层表面结构和疏水性的影响规律;分析了复合镀层表面和截面的结构形貌特点;研究了电刷移动速度对复合镀层中n-SiO2含量的影响规律。对镀层的接触角、表面粗糙度和显微硬度进行了表征。结果表明：刷镀电压和刷镀时间是影响复合镀层表面微观结构特征的重要因素;复合镀层表面的微纳米双重结构对表面的超疏水性起到了关键的作用。     

Wettability characterization and adhesion enhancement of arc-treated surface of aluminum alloys

The aim of this study is to determine the wettability-enhancing effects of an atmospheric pressure, direct current (DC) plasma arc discharge on the surface of aluminum alloys. Wettability is a critical factor in engineering applications such as biomedical implants, painting, and adhesive bonding. For example, in the realm of adhesive bonding, greater wettability improves a metal substrate's attraction to an adhesive material and results in a higher bond quality. In this study, the contact angle was determined and compared as a measure of the wettability using two different techniques: the sessile drop and the ballistic deposition with water as a test liquid. The effect of different arc discharge process parameters on the wettability, including arc current and plasma torch velocity, was studied. A two-dimensional finite element analysis based on the volume-of-fluid model was carried out to explore the behavior of droplet (e.g., spreading and stabilization) on an ideal surface. Additionally, the values of the dynamic receding contact angle were measured through the simulation by applying the tilted plate method and considering the surface roughness to compare the results with the values obtained from the ballistic deposition method. Studying the wettability alteration of the surface of aluminum alloys subjected to the arc treatment revealed the wettability reduction over time. Additionally, it was found that there was a linear correlation between the contact angle value and the strength of adhesively bonded joints using two structural adhesives. The results of this study in the wettability modification of aluminum subjected to the arc treatment and wettability alteration of the treated substrate over time may be used as a quality assurance tool to design the production process and achieve the desired quality and strength in adhesively bonded joints.     

微流体芯片仿生可逆封装方法

当2片聚二甲基硅氧烷接触时,黏附阵列中每根绒毛通过侧面与另一层的一根或多根绒毛的侧面接触,形成可逆封装。根据Baney-Hui的弹性圆柱体接触模型,得到了单根绒毛黏附力表达式。接着分别讨论了黏阵列的单面和双面接触形态以及相应封装强度。结果表明,双面接触形态的封装强度更大,最后用模版法制造了黏附阵列。     

A New Method for the Measurement of Real Area of Contact by the Adhesive Transfer of Thin Au film

In this study, a new experimental method is proposed to measure the real area of contact between a ceramic sphere and an Al surface based on the adhesive transfer of the Au film and the scanning electron microscope (SEM) in the back-scattered mode. A thin film of Au is sputtered on the ceramic sphere before the indentation with the Al surface. The success of this method relies on the fundamental assumption that the adhesive transfer of Au only occurs everywhere inside the contact area. A thin polymer (PMMA) film is deposited between gold film and the ceramic surface to further reduce adhesive strength. After indentation, the interfaces of the ceramic sphere and Al surface are observed by SEM. Experimental evidence that the adhesive transfer of the Au film occurs inside the contact area is given. The entire contact regions on the ceramic sphere and the Al surface are captured in the second electron and back-scattered images with a magnification of 220× (resolution: 432 nm, i.e., distance between neighboring pixels). The contact area can be identified based on both the distributions of the ceramic and Au on the ceramic sphere and Al surface, respectively. The back-scattered images with the magnifications of 5000× and 10,000× (resolution: 20 and 4 nm) are captured at four different locations along the radial direction (starting from the contact center), respectively. The real area of contact decreases from the center to the contact edge.     

涂层硬质合金铣刀组织性能研究

针对3种涂层硬质合金铣刀铣削性能差异,通过表面轮廓仪、接触角测量仪,表征涂层的表面状态和基体的硬度,洛氏硬度压痕法和Zeiss超景深三维显微镜表征涂层与基体的结合强度,扫描电镜(SEM)、能量分散光谱法(EDS)分析涂层表面-界面形貌、化学元素分布,铣削420模具钢实验表征切削性能,研究涂层刀具组织差异对切削性能的影响,为涂层选用提供实际和理论依据。结果表明:涂层铣刀铣削性能不仅与涂层种类和结合力相关,还与铣刀基体材料有关。涂层铣刀涂层种类较好,涂层结合力优异,基体脆性小,切削性能优异;涂层刀具涂层种类优异,涂层结合力一般,基体脆性小,切削性能良好;涂层刀具涂层种类优异,涂层结合力良好,基体脆性大,切削性能一般。