不同载荷对HVOF喷涂AlCoCrFeNi高熵合金涂层摩擦学性能的影响

Effect of Loads on Tribological Properties of HVOF Sprayed AlCoCrFeNi High Entropy Alloy Coating

目的提高深地钻探钻具关键零部件的抗磨性能。方法采用超音速火焰喷涂技术(HVOF)制备AlCoCrFeNi高熵合金涂层。采用X射线衍射仪对高熵合金粉末和涂层的相组成进行研究,采用扫描电子显微镜对高熵合金粉末及涂层的微观结构进行分析,使用维氏显微硬度计测得涂层的显微硬度,采用摩擦磨损试验机对涂层在不同载荷下的磨损行为进行研究。采用SEM和EDS对磨痕表面进行分析,采用XPS技术分析磨痕元素成分,利用三维白光干涉形貌仪测量涂层的磨损体积和表面粗糙度。结果HVOF喷涂AlCoCrFeNi高熵合金涂层结构致密,相结构为BCC相,显微硬度达(536±34)HV_(0.2),约为35CrMo钢基体[(278±20)HV_(0.2)]的2倍。随着载荷的增加,涂层的摩擦系数减小、磨损率增大。相同载荷下(6 N),涂层的磨损率约为基体的41%。HVOF喷涂AlCoCrFeNi高熵合金涂层的磨损失效机制为,低载荷下(2 N)主要为氧化磨损伴随着轻微的磨粒磨损;高载荷下(4、6 N)受到反复剪切应力出现疲劳磨损。结论HVOF喷涂AlCoCrFeNi高熵合金涂层具有良好的抗磨性能,可以有效减轻磨损,有望应用于深地钻探钻具关键零部件的表面防护。

The exploration and development of deep and ultra-deep oil and gas resources is an important part of the future energy strategy,and the drilling equipment will be inevitably worn during operation.Using advanced surface engineering technology to strengthen the surface of key vulnerable parts of deep drilling tools can effectively improve drilling efficiency,prolong service life and ensure the operation safety of drilling equipment.At present,there are many studies on the wear properties of the AlCoCrFeNi bulk high entropy alloy,but there are relatively few studies on the wear properties of the AlCoCrFeNi high entropy alloy coating prepared by thermal spraying technology under different loads,especially in the application of key parts of deep drilling tools.In this paper,the AlCrFeCoNi high entropy alloy coating was prepared on 35CrMo steel by High Velocity Oxygen Fuel(HVOF),and then the phase composition of HVOF sprayed AlCrFeCoNi high entropy alloy powder and coating was studied by X-ray diffractometer(XRD).The particle size of the AlCrFeCoNi high entropy alloy powder was measured by a laser particle size analyzer.The microstructure of the powder and coating was analyzed by scanning electron microscope(SEM)and the microhardness of the coating was measured by a Vickers microhardness tester.The wear behavior of HVOF sprayed AlCrFeCoNi high entropy alloy coating under different loads was studied by a friction and wear tester.The worn surface of AlCrFeCoNi high entropy alloy coating was analyzed by SEM and EDS.The elemental composition of the worn surface was analyzed by XPS and the wear volume and surface roughness(Ra)were measured by a three-dimensional white light interference.The results show that HVOF sprayed AlCrFeCoNi high entropy alloy powder is mainly spherical and has good fluidity.The particle size distribution of the powder is 20~60μm.The HVOF sprayed AlCoCrFeNi high entropy alloy coating is well bonded with the substrate,showing a typical mechanical bonding,and the coating thickness is about 330μm.The microstructure of the coating is compact and the phase structure is BCC phase..The coating’s average microhardness[(53634)HV0.2]is roughly twice that of the 35CrMo steel substrate[(27820)HV_(0.2)].With the increase of load,the friction coefficient decreases and the wear rate increases;Comparing the wear rate of the coating with that of the substrate,the wear rate of the coating is about 41%of the substrate under the same load(6 N).The wear failure mechanism of HVOF sprayed AlCoCrFeNi high entropy alloy coating is as follows:under low load(2 N),it is mainly oxidative wear accompanied by slight abrasive wear.Besides,under high loads(4,6 N),fatigue wear occurs when HVOF sprayed AlCoCrFeNi high entropy alloy coating subjected to repeated shear stress.The wear surface of the coating is composed of various oxides,which can effectively reduce the wear.In summary,HVOF sprayed AlCoCrFeNi high entropy alloy coating has good wear resistance and can effectively provide protection for 35CrMo steel substrate,which is expected to be applied to key parts of drilling tools in deep drilling.