【作者】 牛明远；

【导师】 潘秉锁；

【作者基本信息】 中国地质大学 ， 钻井工程， 2010， 硕士

【摘要】 采用冷压浸渍、热压烧结、无压浸渍和低温电镀等常规方法制作的金刚石钻头,钻头胎体材料从宏观角度上看是均质的,钻进过程中经常会出现胎体耐磨性与所钻岩石研磨性不相适应的现象。而且,常规金刚石钻头胎体中金刚石颗粒呈随机无序分布,可能产生聚集与偏析,这会直接影响到钻头的使用效率和寿命。常规金刚石钻头很难同时兼备高效率和长寿命。为协调两者的关系,研究者往往把如何提高钻进时效作为首要解决的问题,如采用金刚石钻头人工出刃处理、优选金刚石参数、改变胎体耐磨性的办法,另外还研制出各种异形唇面钻头和弱包镶金刚石钻头。但是,这些方法只是有限提高了钻进效率,钻头的使用寿命没有得到改善。为此必须研制出钻进时效高、使用寿命长和适用性广的新型金刚石钻头。为了同时实现金刚石钻头的高时效和长寿命,本文设计制备了一种非均质胎体金刚石钻头结构单元,其由粘结层与采用复合电镀工艺制作的硬质颗粒-金刚石工作层相间平铺,经热压烧结后成型。研究分析了非均质胎体金刚石钻头结构单元同岩石的摩擦磨损特性,为今后设计和制造非均质胎体金刚石钻头提供了可靠依据。本论文主要研究了如下几个方面的内容：1.提出了硬质颗粒-金刚石工作层的制作方案,选用铸造碳化钨硬质颗粒作为增强材料与金刚石颗粒通过复合电镀工艺共沉积到镍基金属中,制作出WC-金刚石工作层。采用单因素实验分析方法,研究了复合电镀主要工艺参数对复合镀层中WC颗粒含量、沉积速率以及镀层硬度的影响。复合镀层中WC颗粒含量随着镀液中WC颗粒悬浮量、阴极电流密度及镀液温度的提高,均呈现出先增大后减小的趋势。沉积速率随着镀液中WC颗粒悬浮量的增加而增大,当超过一定值时又开始下降；随着阴极电流密度及镀液温度的增大,沉积速率呈线性上升趋势。复合镀层中WC颗粒含量最多时,复合镀层显微硬度达到最大值。综合分析优化出最佳工艺参数：电沉积Ni-低浓度WC层时选择4 g/L WC颗粒悬浮量,电沉积Ni-高浓度WC层选择6 g/L WC颗粒悬浮量；阴极电流密度：40 mA/cm2;镀液温度：35℃。采用最佳工艺参数,在不锈钢薄板上电镀出镍基金刚石-WC复合镀层。2.设计了两种粘结层胎体配方,一种添加有石墨固体润滑剂,另一种未添加。研究了两种粘结层的性能和摩擦磨损特性：由于石墨属于软质相,与粘结层中其他金属不发生冶金作用,起到了割裂粘结层的作用,因此加入石墨粉后,粘结层硬度下降。石墨粉在粘结层摩擦磨损过程中被不断的挤出,能够在摩擦表面形成一层减摩润滑膜,减小了摩擦系数,可降低胎体的磨损量,提高其耐磨性。观察试样磨损表面形貌,不含石墨粉的粘结层塑性变形严重,磨损机制以磨料磨损为主,而添加了10%wt石墨粉的粘结层,塑性变形不是很明显,磨损机制以疲劳磨损为主。3.设计了六种非均质胎体金刚石钻头结构单元试样。将定量混匀的粘结层粉末放在LY-200T冷压成型机下冷压成1.5 cm×0.85 cm(长×宽)的粘结层。层数相同的粘结层和WC-金刚石工作层相间平铺,采用SM100-A自控智能烧结机在840℃条件下保温3分钟,在35 KN条件下保压4.5分钟,制作出非均质胎体金刚石钻头结构单元。4.采用MG-2000A型高速高温摩擦磨损试验机研究了每种非均质胎体金刚石钻头结构单元试样与天然岩石对磨的摩擦磨损性能。在不含石墨粉的粘结层中布置不同层数的WC-金刚石工作层,试验发现,随着层数的减少,金刚石浓度降低,其抑制胎体塑性变形和抵御磨料切削挤压胎体能力下降,而且破碎的金刚石充当了硬质磨料,加剧了胎体磨损；摩擦面实际接触面积增加,摩擦系数增大,接近粘结层金属胎体的摩擦系数。在添加10%wt石墨粉的粘结层中布置不同层数的WC-金刚石工作层,由于石墨粉能够在摩擦表面形成一层减摩润滑膜,因此随着层数的减少,胎体磨损量降低,摩擦系数减小。在WC-金刚石工作层数相同的前提下,添加有石墨粉的结构单元比不含石墨的结构单元,磨损量和摩擦系数都有所降低。可见,将石墨作为固体润滑剂引入到金刚石钻头胎体中,可以降低磨损量,有利于延长钻头使用寿命；而且,可以减小金刚石钻头与岩石界面的摩擦力,有利于减少摩擦热的生成,有望解决摩擦热对钻头的热损伤问题。5.粘结层和WC-金刚石工作层相间的结构对工作面上金刚石在环向上实现了有序的排列,每颗金刚石都能得到充分利用,因此可以降低金刚石浓度,进而降低制作成本。金刚石前部的粘结层易磨损,使得金刚石前部出刃较高；而后部的Ni-高浓度WC层较耐磨,对金刚石起到了骨架支撑作用,形成拖尾,这种出刃状态的金刚石切削岩石的效率较高。因此,利用这种非均质胎体金刚石钻头结构单元制作出非均质胎体金刚石钻头,它将在拥有较长使用寿命的同时,保持较高的切削效率。改变结构单元中粘结层和WC-金刚石工作层数,可以调整金刚石钻头胎体中金刚石浓度,以适用不同地层条件的钻进。更多还原

【Abstract】 A diamond bit matrix which is always obtained by such traditional methods as infiltration process with cold pressing, hot pressing sintering method, infiltration process with vibration and low temperature electroplating is homogeneous on the macro level. The disharmony between matrix wear resistance and rock abrasiveness often appeared while traditional diamond bit drilling. Distribution of diamonds in matrix is stochastic and disordered., which will bring about asymmetry and have a direct effect on bit’s drilling efficiency and service life. It is difficult to sustain a higher efficiency while having a longer longevity.In order to balance the relationship between efficiency and longevity, researchers have been focusing on the study of how to increase drilling efficiency, and some solutions have already been suggested, such as adopting manual exposure method deal with diamond bit, optimization of diamond parameters, changing matrix wear resistance, and even some various kinds of special shaped bits as well as weakly-bonded diamond bits have been considered. Though we did to some extent get a higher drilling efficiency through these methods, a longer longevity of the tools is yet to be seen. So a new kind of diamond bit with a higher efficiency and a longer service life is favored, people also expect the new bit can be applicated even more widely.In order to achieve high drilling efficiency and long tool life simultaneously, a heterogeneous matrix diamond bit structural unit is designed in this paper; it consists of a bonding layer and a hard particles-diamond composite plating layer. The new matrix bit will not be completed until a process of hot pressing sintering. The study on wear characteristics of friction between heterogeneous structural unit and rock will provide reliable references to the design and heterogeneous matrix diamond bit-making in the near future.The paper has focused on the following issues:1. A scheme on how to manufacture the hard particles-diamond layer has been proposed. The scheme favors a casting carbide tungsten hard particle as the skeleton metal material, which was then deposited on the nickel with those diamond particles by a process of composite electroplating, and a WC-diamond layer will be obtained. The proposition whose aim is to investigate how the main parameters of composite electroplating influences such elements as the composite coating on content of WC particles, the speed of depositing and the hardness of coating, etc. is laid on a basis of single factor design experimental analysis method. The number of those WC particles in the composite coating will at first increase and then decline when there is a higher cathode current density and the temperature of plating solution is higher. The speed of depositing will increase with a larger number of WC particles; however, it will decline again when reach a certain level. The speed of depositing will undergo a linear increase when the cathode current density and the temperature of plating solution become higher. The micro-hardness of composite coating will be maximal when we get the largest number of WC particles in the composite coating. Optimal process parameters of comprehensive analysis will be like this:When the concentration WC coating of depositing is low, a 4 g/L of WC particles will be better, and when the concentration WC coating of depositing is high, a 6 g/L of WC particles will be the choice. As to the cathode current density and the temperature of plating solution, a 40 mA/cm2 and a 35℃will be ok. At long last, deposit a layer of Ni-diamond-WC composite coating on the stainless steel sheet according to the optimal process parameters.2. Two approaches of layer bonding have been designed. The first one is to put graphite solid lubricant, while the other will omit the graphite. The study investigates the property and wear resistance of two bonding layers. Because graphite is a soft material, and make no metallurgical effect with other metal in bonding layer, which can dissever the bonding layer. Hence, the hardness of bonding layer is reduced with graphite powder. However, the coefficient of friction (abbr. COF) and wear loss will be reduced as graphite will be extruded continuously while the matrix working, which will form a layer of anti-friction lubricant. By observing the sample’s worn surface morphology, it was found that severe plastic deformation appeared on the surface of the bonding layer without graphite, and the main wear mechanism was abrasive wear. While the bonding layer with graphite did not undergo any obvious plastic deformations, its main wear mechanism is fatigue wear.3. Six types of heterogeneous matrix structural units have been designed. A 1.5 cm×0.85 cm bonding layer has been created with a defined quantity of uniform metal powders by LY-200T forming machine. Put the same number of bonding layers of heterogeneous matrix structural units and the layers of WC-diamond in an alternating pattern, then use SM100-A automatic control intelligent sintering machine for temperature-preserve for 3 minutes at 840℃, meanwhile, make sure they are put under a condition of 35 KN for 4.5 minutes. A heterogeneous matrix bit will be expected to be produced.4. Friction characteristics between heterogeneous structural units and natural rocks have been studied with a MG-2000A High-speed & High temperature friction and wear tester. After adding different amount of WC-diamond composite plating layers in the bonding layer without graphite, we found that diamond concentration would reduce along with the decreasing of layer, which could cause diamond to lose some abilities of inhibiting matrix plastic deformation and resisting abrasive cutting-press. Moreover, fragmentized diamonds acted as hard abrasive and aggravated matrix wear loss. The COF increased with the increase of real contact area of friction surface, which was even close to the bonding layer matrix COF. While adding different amounts of WC-diamond composite plating layers in the bonding layer with ten percent of graphite, we could see a lower wear loss and COF companied by the decrease of composite plating layers. The reason is that the graphite powder has produced an anti-friction film on the friction surface. The number of WC-diamond composite plating layers being the same, the wear loss and COF of the structural unit added with graphite was lower than the structural unit without graphite. Obviously, adding graphite solid lubricant into diamond bit matrix could reduce wear loss and COF, thus may help to extend tool life expectancy and decrease the production of friction heat, which is hopeful to solve the bit thermal damage problem caused by friction heat.5. The alternating pattern of bonding layer and WC-diamond working layer makes the diamonds in the friction surface placed in order, so that each diamond grain will be fully used and the total usage be reduced, hence reduce the cost of manufacture. The exposed bonding layer which is on the forefront of diamonds is easy to be worn out, this makes it even good at drilling. While the Ni-high content WC layer which is at the back of diamonds is hard to be worn out, it can serve as a beam for diamond grains and produce a sweeping tail phenomenon. Diamonds under this exposure condition have a great advantage to ensure a higher efficiency of rock-cuttings.In all, heterogeneous matrix diamond bit with heterogeneous structural units will gain a higher drilling efficiency and a longer life span at the same time. The Change of the amount of bonding layers and WC-diamond composite plating layers will adjust the content of diamond bit matrix, and in the end make the matrix better qualified for drillings in different formation conditions.更多还原