后处理对粗晶WC-10Co硬质合金的影响研究
发布时间：2018-09-11 09:31
【摘要】：随着矿山、油气资源开发和基础设施建设的迅速发展,对新一代高效、长寿命粗晶超粗晶矿用硬质合金的需求量日益增加。现代采掘业高冲击载荷、热冲击以及强烈磨料磨损的工况条件,对硬质合金矿用工具材料的性能要求非常高。深冷处理和时效处理是能有效改变金属材料组织结构与合金性能的后处理工艺。将深冷处理和时效处理工艺应用于粗晶超粗晶矿用硬质合金有重大的研究价值和应用前景。本论文以粗晶WC-10Co硬质合金为研究对象,制备了四种不同碳含量的粗晶WC-10Co硬质合金样品,并对试样进行了空白对照、深冷处理以及回火+深冷处理三种处理工艺后,采用电解选择性腐蚀法溶除WC-Co硬质合金表层中的WC硬质相,研究了腐蚀时间、WC粒度、Co相含量对WC选择性腐蚀速度的影响;研究了不同处理工艺对不同碳含量硬质合金样品的力学性能、饱和磁化强度、相结构、显微组织和冲击磨粒磨损性能的影响,并结合实验结果讨论了影响机理;通过与国内外相关研究进行对比,得出以下结论:(1)对于WC-6Co～WC-14Co的粗晶硬质合金,合金中WC硬质相的电解腐蚀速率与腐蚀时间、WC粒度以及Co含量密切相关。在常规电解腐蚀条件下,当选择性电解腐蚀9h时,可获得最佳的合金表层中WC相溶除效果;(2)硬质合金的耐冲击磨粒磨损性能与硬质合金的含碳量以及后处理方式密切相关:通过降低含碳量,可使烧结合金的冲击磨粒磨损量降低60%以上;通过回火+深冷处理,可使合金的冲击磨粒磨损量进一步降低20%以上;(3)深冷处理以及回火+深冷处理后硬质合金的显微组织结构未发生明显改变。但HRTEM观察发现:烧结态低碳WC-10Co硬质合金的Co相中存在着少量成分为WxCoyCz、尺寸为3～5nm、与Co相基体形成完全共格界面的球状弥散相;回火+深冷处理后,由于回火(时效)处理时产生原位沉淀析出效应,纳米WxCouCz弥散相的数量明显增加,使合金的维氏硬度(HV30)轻微上升。(4)在不产生η相的前提下,粗晶WC-10Co硬质合金采用较低碳含量和回火(时效)+深冷处理工艺可获得最佳的耐冲击磨粒磨损性能。对于粗晶合金磨粒磨损性能的提升,Co粘结相中原位析出的纳米弥散相的沉淀强化作用至关重要;合金中WC硬质相邻接度的降低对避免应力集中起到了重要作用;深冷处理后合金表面宏观压应力增加有利于抑制合金表面微裂纹的生成与扩展导致的合金早期失效,从而有利于提高粗晶WC-Co合金的耐磨寿命。
[Abstract]:With the rapid development of mining, oil and gas resources development and infrastructure construction, the demand for the new generation of high efficiency, long life coarse crystal cemented carbide is increasing day by day. The working conditions of high impact load, thermal shock and strong abrasive wear in modern mining industry require very high performance of cemented carbide mining tools. Cryogenic treatment and aging treatment are post-treatment processes which can effectively change the microstructure and properties of metallic materials. The application of cryogenic treatment and aging treatment to coarse ultracoarse cemented carbide has great research value and application prospect. In this paper, four samples of coarse crystalline WC-10Co cemented carbide with different carbon content were prepared, and the samples were treated with blank control, cryogenic treatment and tempering cryogenic treatment. The WC hard phase in the surface layer of WC-Co cemented carbide was dissolved by electrolysis selective corrosion method. The effect of corrosion time and content of WC particle size and Co phase on the selective corrosion rate of WC was studied. The effects of different treatment processes on the mechanical properties, saturation magnetization, phase structure, microstructure and impact abrasive wear properties of cemented carbide samples with different carbon content were studied. The conclusions are as follows: (1) the electrolysis corrosion rate of the WC hard phase in WC-6Co~WC-14Co cemented carbide is closely related to the corrosion time and the content of WC and the content of Co. Under the condition of conventional electrolytic corrosion, when the selective electrolytic corrosion is 9 h, The best solution effect of WC in the alloy surface can be obtained. (2) the abrasive wear resistance of the cemented carbide is closely related to the carbon content of the cemented carbide and the way of post-treatment: by reducing the carbon content, The impact abrasive wear of the sintered alloy can be reduced by more than 60%. The impact abrasive wear of the alloy can be further reduced by more than 20%; (3) the microstructure of cemented carbide after cryogenic treatment and tempering cryogenic treatment has not changed significantly. However, HRTEM observation shows that there is a spherical dispersion phase in the Co phase of sintered low carbon WC-10Co cemented carbides with a WxCoyCz, size of 3 ~ 5 nm, which forms a complete coherent interface with the Co matrix, and is treated by tempering at low temperature. Due to the precipitation effect of in-situ precipitation during tempering (aging) treatment, the amount of nanometer WxCouCz dispersion phase increases obviously, and the Vickers hardness (HV30) of the alloy increases slightly. (4) without 畏 phase, the Vickers hardness (HV30) of the alloy increases slightly. Low carbon content and tempering (aging) cryogenic treatment were used to obtain the best impact wear resistance of coarse WC-10Co cemented carbides. It is very important to enhance the abrasive wear properties of coarse grained alloy by precipitation strengthening of nano-dispersed phase precipitated in situ in Co bonded phase, and the reduction of WC hard adjacent joint in alloy plays an important role in avoiding stress concentration. The increase of macroscopic compressive stress on the alloy surface after cryogenic treatment is helpful to restrain the early failure of the alloy caused by the formation and propagation of microcracks on the surface of the alloy and thus to improve the wear resistance life of the coarse grain WC-Co alloy.
【学位授予单位】：北京有色金属研究总院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG135.5
本文编号：2236306
[Abstract]:With the rapid development of mining, oil and gas resources development and infrastructure construction, the demand for the new generation of high efficiency, long life coarse crystal cemented carbide is increasing day by day. The working conditions of high impact load, thermal shock and strong abrasive wear in modern mining industry require very high performance of cemented carbide mining tools. Cryogenic treatment and aging treatment are post-treatment processes which can effectively change the microstructure and properties of metallic materials. The application of cryogenic treatment and aging treatment to coarse ultracoarse cemented carbide has great research value and application prospect. In this paper, four samples of coarse crystalline WC-10Co cemented carbide with different carbon content were prepared, and the samples were treated with blank control, cryogenic treatment and tempering cryogenic treatment. The WC hard phase in the surface layer of WC-Co cemented carbide was dissolved by electrolysis selective corrosion method. The effect of corrosion time and content of WC particle size and Co phase on the selective corrosion rate of WC was studied. The effects of different treatment processes on the mechanical properties, saturation magnetization, phase structure, microstructure and impact abrasive wear properties of cemented carbide samples with different carbon content were studied. The conclusions are as follows: (1) the electrolysis corrosion rate of the WC hard phase in WC-6Co~WC-14Co cemented carbide is closely related to the corrosion time and the content of WC and the content of Co. Under the condition of conventional electrolytic corrosion, when the selective electrolytic corrosion is 9 h, The best solution effect of WC in the alloy surface can be obtained. (2) the abrasive wear resistance of the cemented carbide is closely related to the carbon content of the cemented carbide and the way of post-treatment: by reducing the carbon content, The impact abrasive wear of the sintered alloy can be reduced by more than 60%. The impact abrasive wear of the alloy can be further reduced by more than 20%; (3) the microstructure of cemented carbide after cryogenic treatment and tempering cryogenic treatment has not changed significantly. However, HRTEM observation shows that there is a spherical dispersion phase in the Co phase of sintered low carbon WC-10Co cemented carbides with a WxCoyCz, size of 3 ~ 5 nm, which forms a complete coherent interface with the Co matrix, and is treated by tempering at low temperature. Due to the precipitation effect of in-situ precipitation during tempering (aging) treatment, the amount of nanometer WxCouCz dispersion phase increases obviously, and the Vickers hardness (HV30) of the alloy increases slightly. (4) without 畏 phase, the Vickers hardness (HV30) of the alloy increases slightly. Low carbon content and tempering (aging) cryogenic treatment were used to obtain the best impact wear resistance of coarse WC-10Co cemented carbides. It is very important to enhance the abrasive wear properties of coarse grained alloy by precipitation strengthening of nano-dispersed phase precipitated in situ in Co bonded phase, and the reduction of WC hard adjacent joint in alloy plays an important role in avoiding stress concentration. The increase of macroscopic compressive stress on the alloy surface after cryogenic treatment is helpful to restrain the early failure of the alloy caused by the formation and propagation of microcracks on the surface of the alloy and thus to improve the wear resistance life of the coarse grain WC-Co alloy.
【学位授予单位】：北京有色金属研究总院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG135.5
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