激光熔覆颗粒增强钛基复合材料组织与性能研究

发布时间：2018-04-19 17:28

本文选题：钛基复合材料 + 激光熔覆技术　；参考：《沈阳航空航天大学》2017年硕士论文

【摘要】：钛基复合材料(Titanium Matrix Composites,TMCs)具有比钛合金更高的比强度,以及极佳的蠕变和疲劳性能,且克服了钛合金耐磨性能差、弹性模量低等不足,在航空航天、医疗工程、化学工业等领域得到广泛应用。本文通过激光单道单层扫描实验,探索本课题所需要的TMCs的合适激光工艺参数;采用激光熔覆技术,以TA15和B4C的混合粉末为原料,原位合成以TiB-TiC为增强相的颗粒增强钛基复合材料。借助XRD、SEM、EDS和硬度测试、室温拉伸实验和室温耐磨实验,研究本课题所制得的TMCs的组织、力学性能和耐磨性能。试验结果表明,激光熔覆颗粒增强钛基复合材料的合适激光成形工艺参数范围为:激光功率1600~2000W,扫描速度6~8mm/s,送粉速率7.5~9.5g/min。四种钛基复合材料中增强相的大小和形态存在差异,但由XRD结果表明,四种钛基复合材料的组织均由α-Ti、β-Ti、TiC和TiB四种相组成。钛基复合材料增强相的主要形态有棱柱状、晶须状和近似等轴状颗粒,且随着B4C添加量的增加,原位合成的增强相数量增多,尺寸增大。其中,棱柱状和晶须状的增强相为Ti B,近似等轴状增强相为TiC。而增强相的尺寸大小和形状与其自身的晶体类型及结构和从液相中凝固析出的过程密切相关。TiB为B27结构,易于生成晶须状或棱柱状。而TiC的晶体结构为NaCl型,易于生成等轴状的结构。性能测试的结果表明:随着增强相含量的增加,钛基复合材料的硬度呈增高趋势,摩擦系数变化不大,磨损失重和抗拉强度均呈先减小后增大的趋势,延伸率呈下降趋势。B元素和C元素含量为0.83 wt%和0.44 wt%的钛基复合材料的抗拉强度最高,摩擦系数最小;而B元素和C元素含量为1.2wt%和0.84wt%的钛基复合材料的磨损失重最少,与基材相比减少了47%。钛基复合材料的断裂方式均为准解理断裂,磨损机制均为磨粒磨损和极少量氧化磨损。
[Abstract]:Titanium Matrix composites have higher specific strength than titanium alloy, excellent creep and fatigue properties, and overcome the disadvantages of poor wear resistance and low elastic modulus of titanium alloy.Chemical industry and other fields have been widely used.In this paper, the suitable laser technological parameters of TMCs are explored by single-channel single-layer laser scanning experiment, the laser cladding technology is adopted, and the mixed powder of TA15 and B4C is used as raw material.Particle reinforced titanium matrix composites with TiB-TiC as reinforcement phase were synthesized in situ.The microstructure, mechanical properties and wear resistance of TMCs prepared in this paper were studied by means of XRDX SEM DS and hardness test, room temperature tensile test and room temperature wear resistance test.The experimental results show that the suitable laser forming parameters for laser cladding particle reinforced titanium matrix composites are as follows: laser power 1600 W, scanning speed 6 ~ 8 mm / s, powder feeding rate 7.5 ~ 9.5 g / min.The size and morphology of the reinforcing phases in the four titanium matrix composites are different, but the XRD results show that the microstructure of the four titanium matrix composites is composed of 伪 -Ti, 尾 -TiTiC and TiB phases.The reinforcing phases of titanium matrix composites are mainly prismatic, whisker and nearly equiaxed particles. With the increase of B _ 4C, the number and size of in-situ reinforced phases increase.Among them, the reinforcement phase of prism and whisker is TiB, and the similar equiaxed reinforcement is tic.The size and shape of the reinforcing phase are closely related to its crystal type and structure and the precipitation process from liquid phase. TIB is B27 structure, and it is easy to form whisker or prism.However, the crystal structure of TiC is NaCl type, and it is easy to form equiaxed structure.The results showed that the hardness of titanium matrix composites increased with the increase of reinforcing phase content, the friction coefficient changed little, and the wear weight loss and tensile strength decreased first and then increased.The tensile strength and friction coefficient of titanium matrix composites with 0.83 wt% and 0.44 wt% C elements were the highest and the friction coefficient was the lowest, while the wear weight loss of titanium matrix composites with 1.2wt% and 0.84wt% of B and C elements were the least, and the tensile strength and friction coefficient of titanium matrix composites with 0.83 wt% and 0.44 wt% of C elements were the lowest, respectively.There is a reduction of 47% compared with the base material.The fracture modes of titanium matrix composites are quasi-cleavage fracture, wear mechanism are abrasive wear and very little oxidation wear.
【学位授予单位】：沈阳航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB333

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