【作者】 高明媛；

【导师】 梁京；

【作者基本信息】 东北大学 ， 材料学， 2009， 硕士

【摘要】 为了增强钛合金表面的耐磨性,按照复合材料的发展趋势,本实验采用TC4(Ti-6A1-4V)粉和B4C粉/C+B粉混合粉作为钛合金表面激光熔覆材料,选用TC4合金作为基体材料,制备原位生成TiC和TiBx复合耐磨涂层,并进行激光快速成形钛基复合材料的探索性试验研究。本文主要以90%TC4+10%B4C(wt.%)粉末为原料,通过预置粉末法制备了单道熔覆层、多道搭接涂层；在此基础上,自行设计激光同步同轴送粉的分粉器、送粉头等装置,通过同步送粉激光熔覆工艺制备了单道熔覆层和单道三层熔覆层(激光快速成形单壁式板材试验样品),应用XRD、金相显微镜、SEM、TEM、EPMA、显微硬度测量仪、磨损试验机等多种分析手段对所制备的多种熔覆层的微观结构和性能进行了研究。通过一系列实验研究得到预置粉末法激光熔覆的优化工艺参数为：离焦量15mm,激光脉冲电流150A,激光扫描速度3.0mm/s。同步送粉法激光熔覆的优化工艺参数为：离焦量为20mm,激光脉冲电流250A,激光扫描速度为0.3mm/s；相应的送粉参数为：氩气送粉气流量为8L/min,送粉速率为9.97g/min,粉末与激光束交点略高于试样表面。试验结果表明：在优化参数下,各激光熔覆层均含有两种以上大量原位生成的陶瓷增强相,并且TC4粉末经激光扫描形成基底黏结相。其中,预置90%TC4+10%B4C (wt.%)粉末的单道激光熔覆层原位生成的增强相为TiC(枝晶状或弥散点)和TiB(针状),多道搭接涂层中还有少量的TiB2生成。多道搭接涂层的平均显微硬度(HV650)较基体(HV320)提高了一倍,其磨损失重量为0.0021g远低于基材TC4的磨损失重量(0.0077g),耐磨性较基体提高了三倍以上。通过热震试验表明基体与涂层之间结合牢固。相同配比的粉料以同步送粉法激光熔覆制得的涂层原位生成的主要增强相为TiB2,TiB。同时生成了少量TiC还有些未反应的B4C,其中TiB2显示为长棒状,及少量六棱柱状,TiB为细长棒状或细小针状。采用优化工艺参数通过同轴送粉成功制备TC4/(TiBx+TiC)激光快速成形钛基复合材料单壁板材试验样品,并对其显微组织进行了初步研究。更多还原

【Abstract】 To develop the wear resistance of the surface of titanium alloys, according to the tendency of the development of composite materials, TC4 powder together with B4C or C/B powder mixture was used as the laser cladding materials on the surface of TC4 titanium alloy substrates. Wear resistant composite coatings were prepared in-situ. The experimental study of direct laser fabrication of titanium matrix composites was also carried out.In this experiment, mix powder with the ratio of 90%TC4+10%B4C (wt.%) was first prepasted on TC4 substrates, on which single and multi-path layers were prepared with laser cladding technology. Based on the results from the laser cladding of prepasted layers, a powder feed head of the synchronized coaxial powder feed laser cladding system was designed by ourselves though which single-path layers and a direct laser fabricated thin wall specimens were prepared. Microstructure and components of the cladding layers were characterized using OM, SEM,TEM, EPMA and XRD. The microhardness of all the specimens and the wear resistant properties of multi-path coatings produced by laser cladding prepasted layers were measured.Optimized processing parameters were obtained though a series of experiments. The optimized laser processing parameters for pre-pasted single-path laser cladding layers were as follow:defocusing distantce of 15mm, laser pulsed current of 150A, laser scanning speed of 3.0mm/s. The optimized parameters of synchronized powder feed laser cladding were as follow:defocusing distance of 20mm, laser pulsed current of 250A, laser scanning speed of 0.3mm/s; the relevant.powder feed parameters:Ar gas powder feed flow rate of 8L/min, powder feed rate of 9.97g/min.Experimental results show that two and more kinds of ceramic reinforcements were in-situ formatted in the matrix of TC4 (Ti-6A1-4V). TiB and TiC ceramic were formed evenly with the morphology of needle, tiny dendrites and disperse particles in the single-path specimens and a small amount of TiB2 in the muitl-path prepasted laser cladding specimens.The average microhardness of the multi-path layer was 650 HV which is twice of that of the substrate (320HV). The wear weight loss is 0.0021g which is far lower than that of the substrate (0.0077g) as well. The wear resistant properties increased over 3 times. Strong connects between coatings and the substrates were also formed according to the thermal shock experiemnt results.The single-path layers of the raw materials with same component ratio were formed by synchronized coaxial powder feed laser cladding system as well. The main ceramic reinforcements were TiB2 (hexagonal prism and rodlike) TiB (needlelike) a small amount of TiC (disperse particles) and some un-reacted B4C.A Ti-6A1-4V/ (TiBx+TiC) thin wall specimen was successfully prepared using the optimized processing parameters of the synchronized coaxial powder feed laser cladding. Primary study on its microstructure was also carried out.更多还原