【作者】 李立波；

【导师】 唐霞辉；

【作者基本信息】 华中科技大学 ， 物理电子学， 2005， 硕士

【摘要】 本文系统地研究了金刚石微粉压坯在高功率CO2 激光作用下的烧结工艺。结合金刚石微粉与金属粉末粘结状态的微观分析,介绍了金属粉末与金刚石微粉浸润性的不同特点,以指导金属粉末体系的选择和设计。建立了金刚石微粉烧结成型质量与激光功率和扫描速度间关系的基本框架,以利于工艺参数的选择、设计和优化。工艺试验研究表明:①在非保护性烧结气氛下,含Ti 的粉末压坯更易被氧化,粉末对微粉润湿性较差,耐磨性能较低。②激光功率的适量增大(扫描速度的适量减小),有利于烧结件的致密化和强碳化物形成元素对金刚石微粉的浸润,但若激光输入线能量超过一定阈值,将会导致微粉的烧损。光斑直径为8.5mm 时,在激光功率550W、扫描速度1100mm/min 烧结条件下,微粉工具具有最佳的烧结性能。③同一工艺参数条件下,由于激光加热和压坯成分的非均匀性,微粉表面状态及其与金属的结合性能存在差异。针对在激光烧结过程中出现的各种不同现象,对其烧结机理作了深入细致的研究,确立了适于金刚石微粉压坯激光烧结的热力学框架,为实际烧结过程提供了可靠的理论依据。理论研究表明:①激光功率达到烧结阈值时,低熔点金属粉末才开始熔化,烧结开始进行; ②激光烧结过程持续时间短、液相流动慢,熔化的液相金属基本只与其周围的高熔点金属粘结。本文在国内首次提出利用激光束来实现金刚石微粉工具的烧结,以解决微粉工具中异形件的烧结难题,拓展了激光加工技术的应用领域,改进了传统的金刚石工具烧结方法。更多还原

【Abstract】 The sintering technique of diamond fine powders compact by CO2 laser has been researched systematically in the thesis. On the basis of the microanalysis on the combination between diamond fine powders and metallic powder, the permeability between them is introduced in order to guide the choice and design of the system of metallic powder. The influences of laser power and scanning speed on sintering performances are studied to choose and optimize the sintering parameters. The research shows: ①Powder compacts with Ti are oxidized more easily at the non-shield atmosphere. ②Laser power is higher (scanning speed is slower), but it could not surpass a critical value, both qualities of the sintering workpiece and combination of diamond fine powders and metallic element are better. With the parameter of 550W laser powder and 1100mm/min scanning speed, the best sintering workpiece can be obtained. ③At the same processing parameter, surface state and relation with metallic matrix of diamond fine powders are different. Further theoretical research on sintering mechanism has been done on the basis of phenomena observed in the sintering experiments. And thermodynamic behavior of the sintering is discussed in detail. The analysis indicate: ①metallic powder with low melting point will not melt down and sintering will not begin until the laser power reach a critical value. ②Laser sintering is so fast that the melted liquid metal is only linked with high-melting-point powder neighboring. It is the first time to manufacture complicated diamond fine powders tools by laser sintering. The field of laser processing is broadened and traditional sintering means of diamond tools are improved.更多还原