纳米晶WC-6Co复合粉合成及特性研究

使用喷雾转化、煅烧和原位还原碳化技术制备了纳米晶WC-6Co复合粉末。通过XRD研究相组成发现,经过喷雾转化处理后粉末为无定形相、经煅烧后的粉末为WO3与Co3O4相、经还原碳化工艺后的物相是WC与Co相;由于Co对碳化过程的催化作用,将煅烧后的粉末置于氢气气氛中加热至900度还原碳化1个小时,即可将粉末碳化完全,制备出WC与Co相共存的纯净复合粉。文章还研究了还原碳化温度（700-900 ℃）对粉末相组成的影响,并通过SEM和HRTEM观察粉末形貌与微观组织。结果表明：制备的粉末具有球形结构,WC晶粒约0.36 μm,亚晶尺寸约为56 nm,说明WC晶粒是多晶体。同时发现粉末中的WC单颗粒被Co相互粘结在一起,且在WC与WC颗粒的接触部位发现存在烧结颈。文章还讨论了复合粉球形结构的形成过程和机理。     

纳米晶WC-6Co复合粉合成及特性研究（英文）

使用喷雾转化、煅烧和原位还原碳化技术制备了纳米晶WC-6Co复合粉末。通过XRD研究相组成发现,经过喷雾转化处理后粉末为无定形相、经煅烧后的粉末为WO_3与Co_3O_4相、经还原碳化工艺后的物相是WC与Co相;由于Co对碳化过程的催化作用,将煅烧后的粉末置于氢气气氛中加热至900℃还原碳化1 h,即可将粉末碳化完全,制备出WC与Co相共存的纯净复合粉。研究了还原碳化温度(700～900℃)对粉末相组成的影响,并通过SEM和HRTEM观察粉末形貌与微观组织。结果表明:制备的粉末具有球形结构,WC晶粒约0.36μm,亚晶尺寸约为56 nm,说明WC晶粒是多晶体。同时发现粉末中的WC单颗粒被Co相互粘结在一起,且在WC与WC颗粒的接触部位发现存在烧结颈。还讨论了复合粉球形结构的形成过程和机理。     

超细晶碳化钨-钴复合粉短流程制备工艺研究

以偏钨酸铵、醋酸钴及葡萄糖为原料,采用短流程工艺,通过喷雾转化法制备出含W、Co等元素的前驱体粉末、煅烧制备W、Co的氧化粉、最后以低温连续还原碳化法制备出WC晶粒尺寸约为260 nm的WC-Co复合粉。研究了短流程工艺3个关键步骤的参数变化对粉末形貌、粒径、氧含量、总碳和化合碳含量等特征的影响。结果表明,当溶液浓度为60%、进料速度为2 000 mL/min、离心转速为12 000 r/min时,制备的前驱体粉末粒度分布均匀,相互粘结的现象较少。温度为550℃、保温时间20 min时煅烧前驱体制备出的氧化物粉末粒度较均匀。当低温连续还原碳化温度为900℃、氢气流量为1.3 m3/h、保温时间为60 min时,可获得WC晶粒细小均匀、总碳和化合碳较为一致且接近于理论碳含量的WC-Co复合粉。     

直接碳化与煅烧-碳化工艺对WC-Co复合粉性能的影响

以偏钨酸铵、醋酸钴、裂解碳为原料,配置成料浆,通过喷雾干燥-氢气还原碳化(简称直接碳化法)和喷雾干燥-氮气煅烧-氢气还原碳化(简称煅烧-碳化法)制备WC-Co复合粉。对两种工艺制备粉末的性能和形貌进行对比,发现直接碳化法制备的WC-Co复合粉的颗粒在10¹00μm、平均粒度在50μm,大部分球形壳破裂,粉末仍然保持球形骨架,粉末松装密度小、流动性差;煅烧-碳化法制备的WC-Co复合粉末的颗粒度在10100μm、平均粒度在50μm,大部分球形壳破裂,粉末仍然保持球形骨架,粉末松装密度小、流动性差;煅烧-碳化法制备的WC-Co复合粉末的颗粒度在10⁵0μm、平均颗粒度25μm,粉末球形度高、流动性好。将两种工艺制备的粉末制成YG6合金,对比发现直接碳化法得到WC-Co复合粉制备成的硬质合金硬度高、晶粒度小、密度高、孔隙度低、致密度高;将两种工艺制备的粉末进行热喷涂,发现煅烧-碳化法制备的粉末热喷涂时,涂层表面致密度高、WC保留率高、硬度高。     

碳氢协同还原-碳化法制备纳米WC粉的工艺及机理

针对传统还原-碳化工艺中WC粉颗粒长大的问题,采用碳氢协同还原-碳化法制备纳米级球形WC粉,研究了前驱体配碳比和反应温度对WC粉性能的影响。结果表明,WC粉的碳含量与前驱体的配碳比密切相关,最佳配碳比(即n(C)/n(W)值)为3.6。W转变为WC具有结构遗传性,WC粉的平均粒径与还原温度和碳化温度密切相关。随着还原温度由680℃升高至800℃,还原水蒸气与碳反应生成CO和H_2,显著降低体系中水蒸气的分压,从而抑制中间产物W颗粒的挥发-沉积长大,WC粉的平均粒径随还原温度升高而减小。碳化过程中的高温促进WC颗粒的晶界迁移和纳米W颗粒之间的烧结合并长大,WC粉的平均粒径随碳化温度的升高而增大。n(C)/n(W)为3.6的前驱体粉末经800℃还原和1100℃碳化后,得到平均粒径为87.3 nm的球形WC粉。     

原位合成复合粉制备超细WC-Co硬质合金

以偏钨酸铵、可溶钴盐、可溶碳源为原料,经喷雾转化、煅烧、低温还原碳化制备超细晶WC-Co复合粉;采用同样成分配比及工艺,在煅烧后增加短时球磨工艺,制备出另一种超细晶WC-Co复合粉;分别以2种复合粉为原料,用放电等离子直接烧结制备超细WC-Co硬质合金。采用SEM、XRD、钴磁仪、矫顽磁力计、维氏硬度计等对复合粉形貌、合金显微组织与性能进行表征分析。结果表明,未短时球磨的粉末呈现出球形结构,WC颗粒被Co相粘结在一起,可观察到烧结颈并有异常长大晶粒,经过短时球磨工序制备的粉末为分散颗粒,2种粉末中Co相同时以fcc与hcp的结构存在,粉末WC晶粒尺寸约为0.26μm;未短时球磨的粉末制备的合金存在少量孔隙,致密度较低,有异常长大晶粒。短时球磨能有效提高粉末颗粒的分散性,减少烧结体中的显微组织缺陷,制备的合金综合性能得到提高。     

碳氢协同还原-碳化法制备纳米WC粉的工艺及机理研究

针对传统还原-碳化工艺中WC粉颗粒的长大问题,采用碳氢协同还原-碳化法制备纳米级球形WC粉,研究前驱体配碳比和反应温度对WC粉性能的影响。结果表明,WC的碳含量与前驱体的配碳比密切相关,最佳配碳比（即n(C)/n(W)值）为3.6。W向WC的转变具有结构遗传性,WC的平均粒径与还原温度和碳化温度密切相关。随着还原温度由680 ℃升高至800 ℃,还原水蒸气与碳反应生成CO和H2,显著降低体系中水蒸气的分压,从而抑制中间产物W颗粒的挥发-沉积长大,WC的平均粒径随还原温度升高而减小。碳化过程中的高温促进WC颗粒的晶界迁移和纳米W颗粒之间的烧结合并长大,WC的平均粒径随碳化温度的升高而增大。n(C)/n(W)为3.6的前驱体粉末经800 ℃还原和1100 ℃碳化后,得到平均粒径为87.3 nm的球形WC粉。     

喷雾干燥法制备球形钨粉及还原过程的研究

以偏钨酸铵(AMT)为原料,采用喷雾干燥法结合氢气还原方法成功制备出球形钨粉。随后利用SEM、TEM、激光粒度分析仪和XRD等分析方法对粉末微观形貌、颗粒平均粒度、粒度分布和还原过程中的相变情况进行研究。结果表明,前驱粉末为球形,煅烧后,颗粒形貌未发生明显变化,仍保持球形;TEM结果显示粉末是球形中空结构。同时探讨了溶液浓度、鼓风速度、给料速度对粉末粒度的影响。激光粒度分析结果表明,溶液浓度对粉末的平均粒度影响最大,溶液浓度越大,颗粒的平均粒度就越大。粒度分布越集中,而给料速度对颗粒的平均粒度影响不明显。XRD结果显示,氢气气氛下,550℃保温2h,α-W相出现;还原温度升高到750℃,保温2h,WO3被完全还原为α-W。     

反应爆炸喷涂制备TiC／Fe-Ni金属陶瓷复合涂层

以钛铁粉、羰基镍粉和碳的前驱体(蔗糖)为原料,通过前驱体碳化复合技术制备Ti-Fe-Ni-C系反应热喷涂粉末,并通过爆炸喷涂技术原位合成并沉积TiC/Fe-Ni金属陶瓷复合涂层;利用XRD、SEM和EDS研究喷涂复合粉末和涂层的相组成、显微结构.结果表明:采用前驱体碳化复合技术制备的Ti-Fe-Ni-C反应喷涂复合粉末粒度均匀;所制备的TiC/Fe-Ni复合涂层由不同含量TiC颗粒分布于金属基体内部而形成的复合片层叠加而成,基体主要是(Fe,Ni)固溶体;TiC颗粒大致呈球形,粒度为纳米级;复合涂层的平均显微硬度HV0.2为18.9 GPa.     

溶胶-喷雾干燥W-Cu前驱体粉末煅烧过程中的相变

采用溶胶-喷雾干燥法制备不同铜含量的W-Cu前驱体粉末,前驱体粉末分别在400、600和800℃各煅烧90min,运用XRD和SEM等手段对煅烧前后复合粉末的相组成和显微形貌进行分析,研究前驱体粉末在煅烧过程中的相变行为。结果表明:前驱体粉末在煅烧过程中发生一系列的分解和化合反应,随着煅烧温度的升高,粉末的相组成、颗粒形貌和尺寸发生明显变化,对W-30%Cu(质量分数)合金,在400℃煅烧后,复合粉末由WO3、CuO和CuWO4组成,粉末颗粒大多呈立方结构,大小为200～400nm;在600℃煅烧后,复合粉末由CuO和CuWO4组成,粉末颗粒大多呈短棒状结构,大小为400～500nm;在800℃煅烧后,复合粉末由CuO、CuWO4和Cu3WO6组成,粉末颗粒大小为3～4μm;前驱体粉末中铜含量对煅烧后复合粉末的相组成也存在较大影响,铜含量越多,越容易生成复合氧化物。     

Synthesis of Cr-doped APT in the evaporation and crystallization process and its effect on properties of WC-Co cemented carbide alloy

WC grain size has significant effect on WC-Co cemented carbide alloy properties. In order to inhibit WC grain growth during sintering process, grain growth-inhibitor Cr₃C₂ is usually added to tungsten carbide powder in advance through mechanical milling. While, homogeneous distribution of Cr₃C₂ in the tungsten carbide powder is difficult to achieve and result in abnormal growth of WC grains. For this purpose of growth-inhibitor uniform distribution, (CH₃COO)₃Cr is added into ammonium tungstate solution during evaporation and crystallization process to prepare Cr-doped APT powder, which can be used as precursor for ultrafine-grained WC-Co cemented carbide alloy preparation. Compared with conventional APT powder, the Cr-doped APT has smaller particle size and bulk density, moreover, chromium is evenly distributed within it. The Cr-doped APT is then used to produce Cr-doped tungsten powder, which also has smaller particle size than that of conventional tungsten powder. Cr-doped tungsten powder is subsequently prepared into tungsten carbide powder and WC-Co cemented carbide alloy through carbonization and sintering process, respectively. Compared with conventional WC-Co cemented carbide alloy, the obtained WC-Co cemented carbide alloy has smaller mean WC grain size (0.36 μm), and more uniform microstructure. Furthermore, the phenomenon of WC grain abnormal growth during sintering process is not observed, because the grain growth-inhibitor Cr₃C₂ is well dispersed in tungsten carbide and cobalt composite powder. Results show that the obtained WC-Co cemented carbide alloy presents better mechanical properties (HRA, bending strength, coercive force) than those of conventional WC-Co cemented carbide alloy. Accordingly, the novel addition of (CH₃COO)₃Cr during the evaporation and crystallization process is the key factor of ultrafine-grained WC-Co cemented carbide alloy production.     

粗晶碳化钨粒度对WC-Co合金晶粒度的影响

选用供应态分别为30μm和12μm的二种粗颗粒WC粉末,研究不同方法表征的粉末粒度与合金晶粒度的关系。结果表明:三种粉末粒度测定方法给出的结果都呈现粒度越粗合金的晶粒度也越粗的规律。粗颗粒WC的研磨态粒度与合金的晶粒度相当接近,金相法测得的12μmWC的晶粒分布与所制备的合金的晶粒度的一致性比30μmWC制备的合金要好。粗晶WC研磨态的Fsss粒度可以用于评价粗晶WC晶粒度,也可以预测WC-Co合金的晶粒度。     

Effects of WC particle size on densification and properties of spark plasma sintered WC–Co cermet

The WC–Co cermet bulks were prepared by spark plasma sintering (SPS) using powder mixtures with different-scaled WC particles. The SPS densification process was studied by calculating the current distribution between the powder sample and the die in the SPS system. The microstructures were characterized and compared for different samples by the WC grain size, Co mean free path and contiguity of WC grains. In spite of a weak effect of WC particle size on the SPS densification stages, the WC particle size plays a significant role in the homogeneity of the cermet microstructure. Good mechanical properties of the SPSed cermet were obtained with an optimized WC and Co particle-size combination. The effects of scale combination of WC and Co particles on the microstructure hence the properties of the SPSed cermet were discussed.     

超细WC-Co硬质合金及其磨损性能研究

采用低温化学镀方法在超细WC颗粒表面进行金属钴包覆,烧结包覆后的复合粉体制备新型硬质合金NYG（WC-3%Co）.研究了超细WC-Co硬质合金的力学性能、断口形貌和显微结构,在销盘式磨损试验机上进行干滑动磨损实验.结果表明,在硬质合金烧结过程中,沿WC晶界均匀分布的金属钴不仅起粘结剂作用,也起抑制剂作用阻碍晶粒的长大;新型硬质合金的抗弯强度、断裂韧性、硬度和耐磨性能均得到较大提高;在干滑动摩擦条件下,新型WC-Co硬质合金的失效以塑性变形及细小碳化钨相颗粒脱落为特征.     

粗晶钨粉碳化过程中粒子间的烧结现象

采用Fsss粒度分别为9μm和21μm的两种钨粉在相同的工艺条件下进行高温碳化,利用扫描电子显微镜、金相显微镜等对样品进行了分析。结果表明,高温碳化过程中会发生粒子间的烧结,碳化温度越高,粒子间的烧结越厉害;钨粉粒度越细越容易烧结;粒度较小的钨粉高温碳化烧结后所得的WC晶粒尺寸虽然会明显增大,但是晶粒度的均匀性下降。     

高线轧制用硬质合金辊环材料的组织与性能

硬质合金辊环材料的组织与性能对钢厂制定配辊方案具有很大的参考价值。本文分析了硬质合金辊环材料的组织和性能特点。其组织与性能由材料中粘结相的含量和WC晶粒大小决定,采用粗晶WC为原料,合金的断裂韧性可达18MPa·m1/2以上,合金的WC晶粒度可达4～5μm,导热率为85～110W/(m·K);减少合金WC/WC界面和WC/Co界面以及WC颗粒的聚集区,可有效地减少热疲劳裂纹源的存在数量,能在一定范围内改善合金韧性和提高合金的抗疲劳性能;合金的磨损性能与粘结相含量、WC晶粒分布和尺寸有很大关系。从WC原料的选择、WC形貌、合金结构和功能材料的应用等方面综述了辊环材料的研究进展,提出了今后研究应重点关注动平衡检测技术在高速轧制技术中的应用、利用计算机对轧制过程中辊环的温度场和应力场进行模拟及磨损机理等方面。     

Optimization of Processing Parameters for WC-11Co Cemented Carbide Doped with Nano-Crystalline CeO2

Nine types of trace nano-CeO₂-doped WC-11Co cemented carbides designed by orthogonal method were prepared. The variance analysis results show that the relative density increases with increasing sintering temperature in the range of 1400-1450 °C; the hardness is highly dependent on grain size of WC which is closely related to the particle size of the initial WC powder and grain refinement produced by nano-CeO₂; the bending strength of WC-11Co cemented carbide with less than 0.15 wt.% of nano-CeO₂ is effectively improved because of its effect on the decreasing of porosity and inhibiting the grain growth of WC and martensitic phase transformation of Co; the fracture toughness rises at the beginning then drops later if the particle size of initial WC powder is in the range of 3-11 μm.     

In-situ metal binder-phase formation to make WC-FeNi Cermets with spark plasma sintering from WC,Fe, Ni,and carbon powders

High-density WC-FeNi ceramic-metal (cermet) composites were fabricated using liquid-phase spark plasma sintering/field-assisted sintering technology (SPS/FAST) with in-situ formation of metal binder phase. The precursor materials were micron-sized powders of WC, Fe, Ni, and C. A low melting point from a eutectic reaction of the powders enabled the in-situ formation of FeNi alloy and facilitates liquid-phase sintering of the WC. The carbon powder was added to stabilize the formation of the binder phase. Electron backscatter diffraction (EBSD) was performed to measure grain size and orientation. The composite exhibited a 99% theoretical density and a microstructure consisting of rounded and contiguous WC grains. The average grain size is 10.5 μm. The composite has a maximum hardness of 16.1 GPa. This research provides a fast and cost-effective approach to fabricate hard metals.     

WC strengthened W–Cu nanocomposite powder synthesized by in-situ reactions

A novel strategy to prepare W–Cu nanocomposite powder with WC nanoparticles for strengthening was proposed. The feasibility and mechanisms of the present in-situ reactions method for synthesizing multicomponent powders were demonstrated by both thermodynamic calculations and experiments. The W-Cu-WC nanopowder can be prepared at a low temperature with pure phase constitution and homogeneous microstructure with a mean particle size of 60 nm. Owing to in-situ reactions, the orientation relationship of WC and W is formed, which facilitates strong bonding between the strengthening particles and matrix. The new method is applicable to synthesize a variety of composite powders with tailorable phase and particle size.