超音速激光沉积制备7075/Al_(2)O_(3)复合涂层的显微组织及性能研究

Microstructure and Properties of 7075/Al_(2)O_(3)Composite Coatings Prepared by Supersonic Laser Deposition

超音速激光沉积是将超音速冷喷涂和激光辐照加热有机结合的一种新型复合材料表面处理技术,具有可制备硬质金属复合涂层、沉积效率高等优点。本工作利用超音速激光沉积技术在7B04铝合金基体上制备硬质铝合金7075与陶瓷颗粒Al_(2)O_(3)的复合涂层,系统研究激光功率对涂层的沉积特性和力学性能的影响规律。采用场发射电子显微镜(SEM)、能谱分析仪(EDS)、X射线衍射仪(XRD)和显微硬度计等仪器,对涂层的显微组织、相成分和显微硬度进行表征分析,结果表明:随着激光功率的增加,涂层的厚度、致密度、沉积效率、硬度以及涂层中Al_(2)O_(3)颗粒的分散性和相对沉积效率逐渐增加。当激光功率为600 W时,涂层的沉积厚度达1543μm,孔隙率为0.05%,涂层中Al_(2)O_(3)粉末颗粒的相对沉积效率达到峰值65%,HV硬度达到1911 MPa。当激光功率提升至900 W时,涂层的厚度、沉积效率增速放缓,孔隙率显著增加,涂层发生氧化相变,Al_(2)O_(3)粉末的相对沉积效率和涂层的硬度下降明显。因而,适当激光辐照的引入有利于提高铝合金颗粒在沉积过程中的塑性变形能力,显著改善涂层的质量。然而,当激光功率过高时,铝合金颗粒的软化现象加剧,且易发生氧化相变,导致涂层的质量下降。

Supersonic laser deposition is an innovative surface treatment technology,which combines supersonic cold spray technology and laser irradiation heating technology.It has the advantages of preparing hard metal composite coating with high deposition efficiency.In this work,composite coatings of hard 7075 Al alloy and Al_(2)O_(3)ceramic particles were prepared on 7B04 Al alloy substrate by supersonic laser deposition technology.The effect of laser power on the deposition characteristics and mechanical properties of coatings was systematically studied.The microstructure,phase composition and microhardness of the coating were characterized and analyzed by field emission electron microscope(SEM),energy dispersive analyzer(EDS),X-ray diffractometer(XRD)and microhardness tester.The results show that with the increase of laser power,the thickness,density,deposition efficiency,hardness and the dispersion uniformity and deposited amount of Al_(2)O_(3)particles in the coating increase.When the laser power is 600 W,the coating thickness reaches to 1543μm,the coating porosity is only 0.05%,the relative deposition efficiency of Al_(2)O_(3)particles is 65%,and the coating HV hardness rises to 1911 MPa.However,when the laser power is enhanced to 900 W,the thickness and deposition efficiency of the coating slow down,and the porosity increases significantly.The oxidation of coating materials is found,and the relative deposition efficiency of Al_(2)O_(3)particles and the coating hardness decrease significantly.In summary,the appropriate amount of laser input is beneficial to improve the plastic deformation of aluminum alloy particles,resulting in significant enhancement of coating quality,while the excessive laser input leads to softening of aluminum alloy particles and even oxidation of powder materials,which deteriorate the quality of deposited coatings.