铁族金属及其盐对人造金刚石单晶腐蚀研究

发布时间：2018-06-15 17:39

本文选题：人造金刚石单晶 + 热化学腐蚀　；参考：《湖南大学》2016年博士论文

【摘要】：金刚石由于具有很高的硬度、耐磨性及较强的化学惰性,因而作为磨粒在硬脆材料加工领域得到广泛的应用。人造金刚石颗粒尺寸较小,通常采用结合剂将它们粘结起来制备成具有一定形状、大小和强度的工具。但由于金刚石单晶表面光滑且表面能较高,在制备金刚石工具时结合剂很难润湿金刚石。因此,两者之间主要以机械镶嵌为主,结合力较弱,磨削加工时大部分金刚石由于过早脱落而造成非磨削损耗。为了提高结合剂对金刚石的把持力,目前采用的方法主要是对金刚石表面进行镀覆或涂覆处理。针对这些处理技术的局限性,论文采用热化学法以铁族金属及其盐对金刚石单晶进行腐蚀。系统研究了各参数变化对铁族金属粉末腐蚀金刚石单晶的影响规律,结合热力学计算,探讨了铁族金属腐蚀金刚石单晶的主要机理;考察了铁族金属盐在不同温度下对金刚石单晶的腐蚀及主要机制;将不同方法处理的金刚石分别与铜基和铁基金属结合剂制备成锯片,对锯片的机械性能和锯切性能进行比较。主要研究结果如下:(1)重点研究了温度对铁族金属腐蚀金刚石的影响。结果表明,温度在腐蚀过程中起关键作用,铁、镍、钴对金刚石单晶腐蚀的初始温度分别为800°C、700°C和600°C。随着温度升高,金刚石单晶的腐蚀程度逐渐加重;当温度相同时,金刚石{100}晶面的腐蚀程度均大于{111}晶面。铁在金刚石{100}晶面的腐蚀主要沿垂直于晶面方向进行,在{111}晶面的腐蚀起源于晶面边缘并逐渐向中心扩展。而镍和钴在金刚石表面的腐蚀均以垂直于晶面方向为主,在金刚石{100}和{111}晶面上形成形状分别为倒金字塔和六边形的腐蚀坑。在试验温度范围内,钴粉对金刚石单晶腐蚀的均匀性较好,且在金刚石{100}和{111}晶面上的腐蚀率和腐蚀深度均大于镍粉。(2)系统研究了保温时间、金属粉末与金刚石比例及金属粉末粒径等对铁族金属腐蚀金刚石的影响。随着保温时间延长,镍和钴腐蚀金刚石后形成的腐蚀坑面积和深度逐渐增大,但当保温时间超过一定值后,延长保温时间对金刚石腐蚀影响逐渐减小。减小钴粉与金刚石的质量比,金刚石{100}和{111}晶面的腐蚀率和腐蚀深度明显降低,同时金刚石表面腐蚀的均匀性变差。此外,随着钴粉粒径增大,金刚石单晶的腐蚀程度变轻且均匀性变差。(3)探讨了铁族金属腐蚀金刚石的机制及腐蚀形貌的形成规律。金刚石腐蚀过程可描述为:随着温度升高,金属逐渐熔融并开始润湿金刚石表面;在金属的催化作用下,金刚石结构碳发生相变转变成石墨结构碳;金刚石与熔融金属界面处形成的石墨以浓度差为驱动力,在金属中向远离界面方向扩散。根据菲克定律对铁腐蚀金刚石的理论腐蚀深度进行计算,结果与试验所测P-V值的变化趋势大体一致。与金刚石台阶状生长模式相似,铁族金属腐蚀金刚石单晶也是通过逐层实现的。对于金刚石表面形成的腐蚀坑,其底部对应于被腐蚀晶面,而其内壁则由被腐蚀晶面的相邻晶面或稳定性更高的次级相邻晶面组成。(4)探索了二水草酸铁、二水草酸钴和六水硝酸钴在不同温度下对金刚石的腐蚀行为及腐蚀机理。随着温度升高,金刚石单晶的腐蚀程度逐渐加重。特别是以二水草酸铁作为腐蚀剂时,当温度超过900°C后,金刚石单晶的腐蚀程度急剧加重。二水草酸钴和六水硝酸钴均可同时在金刚石{100}和{111}晶面上形成腐蚀坑,但与金属钴粉相比,金刚石单晶腐蚀的均匀性较差,而且在同一个晶面上腐蚀坑的大小和深度也有较大差别。二水草酸铁腐蚀金刚石的机理为金刚石石墨化和氧化,而二水草酸钴和六水硝酸钴腐蚀金刚石的主要机理为金刚石石墨化。(5)分析比较了不同方法处理的金刚石及其与金属结合剂复合烧结体的机械性能。与未处理金刚石相比,镀钛金刚石的单颗粒抗压强度和冲击韧性都较高,与铜基结合剂复合制备的烧结体的硬度、抗弯强度和冲击强度均无明显变化,但与铁基结合剂复合制备的烧结体的抗弯强度和冲击强度都略有下降。经钴粉腐蚀处理的金刚石的单颗粒抗压强度和冲击韧性虽然都略有下降,但与铜基和铁基结合剂复合制备的烧结体的抗弯强度和冲击强度均明显提高。(6)通过锯切试验,对比了不同方法处理的金刚石制备的金属基锯片的锯切性能。与未处理金刚石制备的锯片相比,镀钛金刚石与铜基结合剂制备的锯片锯切试验后工作面上金刚石出刃高度无明显变化,但50%出刃比例稍有增加,金刚石脱落率略有下降,锯片锯切寿命提高15%;与铁基结合剂制备的锯片锯切试验后工作面上金刚石出刃高度和50%出刃比例均增加,金刚石脱落率明显降低,锯片的锋利度较差,锯切寿命增加11%。腐蚀处理金刚石与铜基和铁基结合剂制备的锯片锯切试验后工作面上金刚石出刃高度和50%出刃比例均增加,金刚石脱落率均明显下降,锯片自锐性较好,锯片锯切寿命分别提高12%和8%。
[Abstract]:Diamond is widely used in the field of hard and brittle materials because of its high hardness, wear resistance and strong chemical inertness. The size of artificial diamond particles is smaller. Usually, the diamond particles are bonded together to prepare a tool with a certain shape, small size and strength. It is difficult to wetting diamond when making diamond tools. Therefore, the main methods are mechanical inlay and weak binding force between them. Most of the diamond is due to premature loss in grinding. In order to improve the holding power of the bond to diamond, the main methods used are mainly to be used at present. The surface of diamond is coated or coated. Aiming at the limitation of these techniques, the paper uses the thermochemistry method to corrode the diamond single crystal with the iron metal and its salt. The influence of the change of the parameters on the corrosion of the diamond single crystal by the iron metal powder is systematically studied, and the corrosion of the iron metal is discussed by the thermodynamic calculation. The main mechanism of diamond single crystal was studied. The corrosion and main mechanism of the iron metal salt at different temperatures on the diamond single crystal were investigated. The diamonds treated by different methods were prepared with the copper base and iron base metal bond respectively. The mechanical properties and sawing properties of the saw blades were compared. The main research results are as follows: (1) focus on the study. The effect of temperature on the corrosion of diamond by iron metal. The results show that temperature plays a key role in the corrosion process. The initial temperature of iron, nickel and cobalt corrosion of diamond single crystal is 800 C, 700 C and 600 degree C., with the increase of temperature, the corrosion degree of diamond single crystal is gradually aggravated; when the temperature is the same, the corrosion degree of the diamond {100} surface is the same. The corrosion of iron on the diamond {100} surface is mainly perpendicular to the direction of the crystal surface, and the corrosion on the {111} crystal surface originates from the edge of the crystal surface and gradually expands to the center, while the corrosion of nickel and cobalt on the diamond surface is perpendicular to the crystal surface, and the shape of the diamond {100} and the {111} crystal surface is the inverted gold character, respectively. Corrosion pits of tower and hexagon. In the range of experimental temperature, cobalt powder has better corrosion to diamond single crystal, and the corrosion rate and corrosion depth on the {100} and {111} surface of diamond are greater than that of nickel powder. (2) the thermal insulation time, the ratio of metal powder to diamond and the particle size of metal powder have been systematically studied. With the prolongation of heat preservation time, the area and depth of the corrosion pit formed by the nickel and cobalt corrosion diamond gradually increased, but the effect of prolonging the heat preservation time on the diamond corrosion gradually decreased. The corrosion rate and the corrosion depth of the diamond {100} and {111} crystal surface and the corrosion depth were obviously reduced. At the same time, the uniformity of the diamond surface corrosion is worse. In addition, with the increase of the particle size of the cobalt powder, the corrosion degree of the diamond single crystal becomes lighter and the uniformity becomes worse. (3) the mechanism of the corrosion of the diamond and the formation law of the corrosion morphology are discussed. The process of diamond corrosion can be described as the gradual melting and beginning of the metal as the temperature rises. The surface of diamond is wetted. Under the catalysis of metal, the phase transition of the diamond structure changes into graphite structure carbon. The graphite formed at the interface between the diamond and the molten metal is driven by the difference of concentration and diffuses in the metal to the direction of the interface. The theoretical corrosion depth of the corroded diamond is calculated according to the law of Fick's law. The results are calculated. Similar to the P-V values measured by the experiment, similar to the diamond step growth pattern, the iron metal corrosion diamond single crystal is also realized by layer by layer. The bottom of the corrosion pit on the diamond surface corresponds to the corroded crystal surface, and its inner wall is adjacent to the corroded crystal surface or the higher stability of the secondary surface. (4) the corrosion behavior and corrosion mechanism of two oxalate, two cobalt oxalate and six cobalt nitrate at different temperatures were explored. The corrosion degree of diamond single crystal increased gradually with the increase of temperature. The corrosion of diamond single crystal when the temperature was more than 900 C. The degree of the cobalt oxalate two and the six water cobalt nitrate can simultaneously form a corrosion pit on the crystal surface of the diamond {100} and {111}, but compared with the metal cobalt powder, the uniformity of the corrosion of the diamond single crystal is poor, and the size and depth of the corrosion pit on the same crystal surface is greatly different. The mechanism of the corrosion of diamond by two oxalate iron is gold. The main mechanism of the corrosion of diamond by cobalt oxalate two and six water cobalt nitrate is diamond graphitization. (5) analysis and comparison of the mechanical properties of the diamond and the composite sintered with the metal bond treated by different methods. Compared with the untreated diamond, the single particle compressive strength and impact toughness of the titanium plated diamond are compared with that of the untreated diamond. The hardness, bending strength and impact strength of the sintered body prepared with the copper base binder were not obviously changed, but the flexural strength and impact strength of the sintered body prepared with the iron base binder decreased slightly. Although the strength and impact toughness of the single particles of the diamond treated by cobalt powder corrosion decreased slightly, but they were slightly reduced. The flexural strength and impact strength of the sinter prepared by the composite of copper base and iron base binder improved obviously. (6) the sawing properties of the metal base saw blades prepared by different methods were compared by sawing test. Compared with the saws prepared from the untreated diamond, the sawing test of the gold plated titanium carbide and copper base binder There is no obvious change in the height of the diamond cutting edge on the post working face, but the ratio of the 50% cutting edge is slightly increased, the drop rate of diamond is slightly decreased and the sawing life of the saw blade is increased by 15%. The diamond cutting edge height and the ratio of 50% out of the blade on the working face are increased after the sawing test of the iron base bond, and the diamond shedding rate is obviously reduced and the blade sharpness is sharp. After the sawing test of 11%. corrosion treatment of diamond and copper base and iron base bond, the diamond cutting edge height and 50% cutting edge ratio increased, the diamond shedding rate decreased obviously, the saw blade's self sharpness was better, the sawing life of saw blade was increased by 12% and 8%., respectively.
【学位授予单位】：湖南大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ163

【相似文献】