摘要
为提高页岩油气钻进过程中钻头表面的耐磨性能及防泥包性能,采用冷喷涂(CS)和超音速火焰喷涂(HVAF)技术在35CrMo钢基体上制备了Fe48Cr15Mo14C15B6Y2非晶合金涂层,并利用紫外激光制备了涂层的疏水表面,利用扫描电子显微镜(SEM)、X射线能谱仪(EDS)、X射线衍射仪(XRD)测试分析了涂层的微观结构和力学性能,利用接触角测量仪表征涂层的润湿性,并分析其润湿机理。结果表明:利用CS技术制备的Fe基非晶合金涂层结构更加致密,非晶质量分数达到90%,且具有更好的热稳定性。激光过程中的熔融物快速冷却在涂层表面形成纳米尺寸级别的凝结物以及团聚物形成微纳复合结构,在激光扫描次数为7次时,CS涂层表面水接触角最高,具有良好的疏水性。
随着工业经济的快速增长,我国对油气资源的需求也急剧增加,目前我国过高的油气对外依存度已经成为了国家发展能源系统安全的“短板”。我国非常规油气资源储量丰富,致密气、页岩油气、煤层气等非常规天然气地质资源量是全国天然气总地质资源量的近2倍,开发非常规油气资源已成为解决我国能源安全问题的有效途径。泥页岩具有表面积大、空隙小、结构复杂、易溶胀等特性,在钻进过程中钻头极易产生“泥包”现象,即在钻进过程中会产生泥质岩屑,在遇水后不能及时排离孔底而包被在钻头表面。且无论采用什么样的钻头,都会有“泥包”现象产生,导致停钻或卡钻等孔内事故的产生。因此,为保证钻探的安全性和可靠性,制造钻探设备的材料性能尤其是表面性能正面临着严苛的要求和巨大的挑战。为了解决钻头“泥包”问题,本领域研究人员采取的方法之一是在钻头钢体表面制备涂层,通过喷涂技术制备出疏水性和耐磨性均优良的涂层,以解决钻头“泥包”问题和服役持久发展性问
非晶合金(也称为金属玻璃)是在利用超急冷凝固技术制备过程中,熔融状态合金凝固时原子来不及有序排列结晶,因此得到的合金拥有像玻璃一样的长程无序结构——不存在晶态合金的晶粒和晶界。其中Fe基非晶合金以其超高的强度和硬度、优异的防腐耐磨性能、原料成本相对低廉等优势,在矿山、钻井等装备的表面防护领域得到了广泛应用。激光蚀刻作为一种传统的材料去除工艺,已经成为非晶合金微加工的主要研究方向。由于非晶的缺乏晶界等特性,有着较低的导热系数,并且独特的长程无序、短程有序的原子尺度非均匀性,使得易在非晶态合金表面构造微纳米结
为了探究Fe基非晶合金涂层的润湿性,Zhang
此外激光织构加工参数对非晶合金的润湿性也有很大影响。通过调整激光加工织构间距和激光扫描速度等操作参数,可以在非晶合金表面通过激光刻蚀制备出各种微观结构,如凹状微观结构和线性微槽等。Fornell
本研究针对非常规油气资源钻探过程中钻头钢体的“泥包”问题,通过冷喷涂(CS)和超音速火焰喷涂(HVAF)技术制备了Fe48Cr15Mo14C15B6Y2非晶合金涂层,分析了涂层的相组成、微观结构、孔隙率以及显微硬度,进行了涂层在不同加工参数下的激光织构,对涂层的润湿性等进行了分析,探讨了织构化Fe48Cr15Mo14C15B6Y2非晶合金涂层的润湿机理。
实验选用的原料为高纯氩气雾化工艺生产的Fe48Cr15Mo14C15B6Y2(%,原子分数)非晶粉末,粉末粒10~60 μm,其中筛选出10~30 μm的非晶粉末用于冷喷涂技术制备涂层,筛选出20~60 μm的粉末原料用于超音速火焰喷涂制备涂层,并在HVAF粉末原料中按1∶1的比例加入直径为40~70 μm的Al2O3陶瓷颗粒,以避免喷涂过程中熔融液滴因为快速冷却而堵塞枪口,同时也可提升涂层的致密性。基体材料为35CrMo钢,试片尺寸为50 mm×15 mm×5 mm,并对试样进行1 mm×45°倒角以防止在实验过程中产生应力集中导致涂层开裂。
采用德国Impact公司Impact 5/11型喷涂设备进行冷喷涂,采用美国Kermetico公司的喷涂设备进行超音速火焰喷涂,喷枪型号为AK⁃06。2种制备技术的工艺参数如
注: 1 psi=6.895 kPa。
采用场发射扫描电子显微镜(SEM, ZEISS,德国)观察FeCrMoCBY非晶粉末和涂层的微观形貌,并使用X射线能谱仪(EDS)分析涂层的化学成分。采用X射线衍射仪(XRD,Rigaku D/max-2500,日本)对粉末和涂层进行物相分析,入射线为Cu Kα射线,扫描角度为20°~80°,扫描模式选用连续扫描,扫描频率为4°/min。利用MDI-Jade 6.0软件计算粉末和涂层的非晶含量。使用灰度法测量涂层的孔隙率,并利用ImageJ2x软件评估孔隙率值。采用热重法和差热分析法(DTA-TG:STA 449 F3, Netzsch,德国)进行表征,使用氩气作为惰性保护气氛,升温速率10 K/min,温度范围为323~1373 ℃。
加工前先对涂层进行表面预处理,涂层经打磨抛光后分别用丙酮、无水乙醇超声清洗。实验采用世纪镭杰明公司提供的一体式紫外激光加工设备,激光加工的具体参数如

图1 FeCrMoCBY非晶粉末显微形貌
Fig.1 SEM image of FeCrMoCBY amorphous powders

图2 FeCrMoCBY非晶合金涂层表面的微观形貌
Fig.2 SEM images of FeCrMoCBY amorphous
alloy coating

图3 FeCrMoCBY非晶合金涂层截面的显微形貌
Fig.3 SEM images of FeCrMoCBY amorphous alloy coating section

图4 HVAF涂层截面的EDS能谱图
Fig.4 EDS energy spectrum of HVAF coating section
FeCrMoCBY非晶粉末和涂层的物相组成如


图5 FeCrMoCBY非晶粉末和涂层的XRD分析图谱
Fig.5 XRD patterns of CS FeCrMoCBY amorphous
powders and coatings
接触角是表征材料表面润湿性的常用指标。

图7 不同激光织构扫描次数与接触角的关系
Fig.7 Relationship between contact angles and
scan numbers by laser
材料表面润湿性的2个最关键因素是合适的表面特征和较低的表面能。目前已建立2种适用于粗糙表面的不同湿润模型。在Wenzel模型中,表面粗糙度的增加会使亲水表面变得更加亲水,使疏水表面变得更加疏

图8 CS涂层激光微织构三维形貌
Fig.8 3D morphology of CS coating by laser weaving
从

图9 CS涂层激光微织构表面形貌
Fig.9 SEM image of CS coating by laser weaving

图10 CS涂层激光微织构表面的EDS能谱图
Fig.10 EDS energy spectrum of CS coating by laser weaving
(1)相对于超音速火焰喷涂,冷喷涂制备的FeCrMoCBY非晶合金涂层的非晶含量更高,约为90%,涂层更加致密,孔隙率约为1.3%,具有更好的热稳定性。
(2)激光织构后,2种涂层的接触角都显著增加,扫描次数对疏水性影响较大,在扫描次数为7次时疏水角最大,具有较好的疏水性。
(3)同样的激光织构参数下2种涂层的接触角相近但存在差异,主体上是由于表面结构和化学成分的综合作用,点阵织构表面有机碳材料的吸附提升了疏水性。
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