基于张力环试验的热压钻头WC-Cu基胎体对金刚石把持力的定量研究

The drilling efficiency and working life of the diamond bits have an importance on the development and advancement of the technology of wire-line coring drilling in deep drilling. Under the conditions of reasonably determining the structure and the type of drilling bits, their drilling efficiency and working life are depended on the retention of matrix to diamond. It is rarely reported that the related test equipment, the corresponding evaluation method or standard and the quantitative research in the study field of the retention of bit matrix to diamond. In this project, the testing apparatus is developed for the accurate measurement of the holding strength of matrix to diamond based on the test principle of expansion ring. And then, it is quantitatively researched by using the testing apparatus that the influence regularities of the preparation technology, matrix formulation and working temperature of WC-Cu based matrix for the hot-press diamond bits to the total retention, the mechanical retention and the chemical bonding force of matrix and diamond. The forming mechanism of the retention of WC-Cu based matrix to diamond for the hot-press diamond bits are analyzed. The calculation models of the total retention, the mechanical retention and the chemical bonding force of matrix and diamond are established. The theoretical system of traditional matrix formula and manufacture technology is enriched and developed. On the base of the quantitative research to the retention of matrix to diamond, there are important significances in improving the drilling quality and efficiency and reducing the drilling cost through targeting to improve or weaken the holding force according to the needs of drilling.

金刚石钻头的寿命和效率问题对于深部钻探中绳索取心钻进工艺的发展和推进具有重要影响。在金刚石钻头结构和选型合理的情况下，金刚石钻头寿命和效率取决于胎体对金刚石的把持力。而在钻头胎体对金刚石把持力的研究方面，既没有相关的测试设备，也没有相应的评价方法或标准，极度缺乏关于把持力的定量研究。本项目基于张力环试验原理，研发用于精确测量钻头胎体对金刚石把持力的张力环试验装置，然后利用该装置定量地研究热压钻头WC-Cu基胎体的制备工艺、胎体配方和工作温度对总把持力、机械把持力、化学结合力的影响规律，分析热压钻头WC-Cu基胎体对金刚石把持力的形成机制，建立胎体对金刚石的总把持力、机械把持力、化学结合力的计算模型，丰富和发展传统胎体配方和制备工艺设计的理论体系。在钻头胎体对金刚石把持力定量研究的基础上，根据钻进的需要，针对性地提高或弱化把持力，这对于提高钻探质量和效率、降低钻探成本具有重要意义。

胎体对金刚石的把持力极大地决定了金刚石钻头的使用寿命和切削效率，对把持力的控制是研制高性能钻头的关键技术。而在钻头胎体对金刚石把持力的研究方面，既没有相关的测试设备，也没有相应的评价标准，极度缺乏关于把持力的定量研究。针对这些问题，本项目开展了热压钻头WC-Cu基胎体对金刚石把持力的定量研究工作：基于张力环测试原理，研发了一种评价把持力的测试装置；建立了胎体对金刚石把持力的计算模型；研究了WC-Cu基胎体配方、热压工艺、金刚石镀覆、预合金粉末、金刚石浓度、粒度等对把持性能的影响。结果表明：WC、YG8、663-Cu含量变化对把持能力的影响不显著；胎体的弹性模量和热膨胀系数对把持力影响显著，而胎体的泊松比对把持力的影响很小；弹塑性胎体相比于弹脆性胎体，由于塑性变形，释放了部分能量，减少了界面处胎体热应力产生裂纹的可能，可以改善胎体对金刚石的把持能力，另外，胎体屈服强度的提高有助于增加把持能力；在试验范围内，烧结温度、烧结压力和出炉温度对把持力有一定的影响，升温速度和保温时间对把持力影响很小，改善烧结工艺参数对于提高胎体的把持力有积极意义，但对WC-Cu基胎体来说，仅通过改善烧结工艺参数无法有效提高胎体的把持能力；金刚石表面镀钛对把持力有一定提升作用，钛镀层厚度对把持力影响比较显著，随钛镀层厚度从1μm到3μm时，其热应力显著减少，从而降低了冷却过程中的热损伤，保证了胎体的把持力，但镀层厚度继续增加，其应力变化并不明显，反而会降低胎体对金刚石的机械镶嵌力；胎体粉末的预合金化有助于降低胎体烧结温度，增加胎体对金刚石的把持能力，预合金粉末的加量需要合适的比例，否则会影响胎体的力学性能；胎体对金刚石把持力随金刚石体积分数增加而减少，随金刚石粒径减小而增加；随胎体工作温度的增加，胎体对金刚石把持力不断降低。项目研究成果有助于使金刚石钻头胎体配方的设计和制备工艺的优化更为科学和简便。