冷喷涂硬质合金耐磨涂层研究进展

硬质合金涂层具有高耐磨性与高耐腐蚀性等优势,因此广泛应用于冶金等领域的耐磨、耐蚀防护中。采用传统热喷涂技术制备硬质合金涂层,其高温会导致涂层材料产生相变、氧化、脱碳等问题,从而损害涂层的服役性能。冷喷涂技术作为一种新兴的涂层制备技术,具有低温的特点,可避免传统热喷涂方法所带来的涂层质量问题,成为硬质合金涂层制备的潜在技术。在简述冷喷涂技术原理及其沉积机理的基础上,综述了冷喷涂制备硬质合金耐磨涂层(如WC-Co、WC-Ni、Cr3C2-NiCr等),以及影响涂层硬度、耐磨性等力学性能的主要因素,包括硬质相、黏结相的种类、含量和尺寸等。综合比较了冷喷涂与超音速火焰喷涂制备的硬质合金涂层的耐磨性能,分析了后处理(喷后热处理、搅拌摩擦处理)对冷喷涂硬质合金涂层耐磨性的影响。最后,提出了冷喷涂技术在硬质合金耐磨涂层制备方面的局限性,并对未来发展进行了展望。     

无粘结相WC硬质合金的研究进展

无粘结相WC硬质合金(Binderless tungsten carbide, BTC)是WC硬质合金领域的研究热点,BTC具有较高熔点及良好的耐腐蚀性,与WC-Co等金属作为粘结剂的WC硬质合金相比,更适宜应用于高温、腐蚀性强等恶劣环境中。同时,BTC还具有高硬度以及良好的耐磨性等优异性能,是具有应用潜力的硬质合金材料。但是,其致密化温度高,采用传统的烧结方法很难使其致密化,在烧结过程中易发生晶粒异常长大,韧性较低。因此,一些研究人员将金属碳化物、金属氧化物以及碳材料等非金属添加剂加入其中,用于改善BTC的烧结性能、抑制烧结过程中的晶粒长大现象以及改善其力学性能,相关研究已经取得了一定进展。本文从BTC材料的分类、性能、制备方法、应用等方面对BTC的相关研究成果进行综述。在BTC分类中主要介绍不同陶瓷结合剂的添加对其性能的影响,对比了不同种类的BTC的性能差异,介绍了制备BTC材料常用的传统及先进的烧结技术。     

钢铁表面高强韧涂层的研究进展

在钢铁材料表面制备硬质涂层,可明显改善其表面硬度低和耐磨性差而导致在摩擦工况下使用寿命低的问题.然而传统均质涂层在提高强度、硬度和耐磨性的同时,会大幅降低其韧性,即强度和韧性呈现"倒置关系".针对强度-韧性的"倒置关系",设计并开发出具有高强、高韧、高耐磨的涂层,对扩大钢铁材料的应用具有重大意义.从制备工艺、微观组织、力学性能以及强韧化机制等方面,综述了钢铁表面层状结构涂层、多尺度结构涂层、梯度结构涂层和纳米结构涂层等几种高强韧涂层的研究进展.在此基础上,指出钢铁表面高强韧涂层未来应向开发新型表面改性技术、设计与精确调控多元多尺度复合构型以及构建微观组织-力学性能数值模型的方向发展.进一步提出了钢铁表面多元多尺度结构涂层的可控制备技术原型,即通过新型表面改性技术与理论计算、仿真模拟的协同配合,实现钢铁表面多元多尺度结构涂层的进一步优化设计与精确调控,建立微观组织-力学性能之间的函数关系,准确揭示其强韧化机理,为突破强度-韧性"倒置关系"瓶颈,实现综合性能优异的钢铁基表面复合材料的制备提供新思路.     

Ru添加对WC-Co硬质合金结构与性能的影响

粘结相是硬质合金重要的组成部分,随着硬质合金材料技术的发展,目前,越来越多的研究者希望能够通过粘结相的掺杂技术来提升合金的综合性能。本文通过对比分析WC-Co和WC-Co-Ru硬质合金,发现Ru的添加能够抑制WC晶粒的长大,有效抑制WC晶粒的异常长大,可以提高合金中粘结相Co的显微硬度和合金的整体硬度,能够显著提升硬质合金的高温抗氧化性,在粘结相结构方面,Ru元素会促进钴的亚稳态α-Co相向室温稳定态ε-Co相的转变。经过镍基高温合金车削和钛合金铣削对比实验,Ru添加硬质合金表现出更好的耐磨性、抗冲击韧性以及高温抗氧化性。     

采用复合硬质合金牌号的高性能旋转刀具基体

用于金属切削的旋转刀具通常采用硬质合金（WC）作为基体材料，这是由于硬质合金在强度、耐磨性、抗破裂韧性等机械性能上具有独特的综合优势。传统的整体硬质合金旋转刀具都是采用单一结构的基体材料，即整个基体都用同一种硬质合金牌号制造，这种结构的刀具在使用性能上存在较大的局限性。     

工具的材料和涂层对其切削性能的影响

对同种材料不同涂层和不同材料同种涂层的刀具进行了切削试验。结果表明,在铣削淬硬的40Cr钢时,用硬质合金A制作、带TiAlCN涂层的6刃立铣刀使用寿命最高。这既与涂层的耐磨性、表面粗糙度和抗氧化性能有关,也与硬质合金A的硬度、韧性和抗弯强度有关。     

WC-Co复合粉末的原位合成及于硬质合金涂层制备中的应用

目的为解决超细/纳米WC-Co热喷涂时易于脱碳等瓶颈问题,制备具有高的硬度、断裂韧性、耐磨性和表面质量等优异综合性能的超细及纳米结构硬质合金涂层,并推广其在工业领域中的应用。方法以原位合成技术批量制备的超细/纳米WC-Co复合粉末为原料,利用团聚造粒技术制备得到具有高球形度和致密性,并保持原有超细/纳米结构的喷涂喂料粉末,利用超音速火焰喷涂工艺制备低脱碳、高致密的超细结构WC基涂层。结果降低喂料粉末孔隙度可有效减少涂层中W2C等脱碳相的含量,在优化工艺下制备的超细结构WC基涂层的硬度达到1450HV0.3以上,韧性相对于常规微米结构涂层提高40%以上,在两种载荷和磨料条件下均表现出更高的耐磨性。结论利用原位反应技术批量合成的超细/纳米WC-Co复合粉制备的硬质合金涂层具有优良的综合性能,可应用于对涂层的硬度、耐磨性、强韧性配合和表面质量有较高要求的工况。     

我国硬质合金焊接刀片和凿岩工具用硬质合金制品质量现状及其分析

1前言我国是硬质合金生产大国。建国以来，我国硬质合金行业从无到有，从小到大，已逐步形成牌号齐全、规格配套的较完整生产体系，为国民经济发展作出了重要的贡献。硬质合金具有高的硬度和耐磨性，并具有一定的强度和韧性，它作为一种优良的硬质工具材料已广泛应用于机械切削     

新型模具材料—KF2合金

<正> 工具材料已开发出从工具钢到 CBN(立方氮化硼)、金刚石等种类繁多的品系。从用量上来看,高速钢和硬质合金占大部分,但它们却非万能,而是各有短长,高速钢的韧性较高而耐磨性较低,硬质合金则耐     

美国肯纳公司推出用于精密冲模的新型硬质合金材料CD-KR887

硬质合金因其具有高耐磨性和良好的抗冲击性能，被越来越广泛地应用在精密冲模制造领域。硬质合金在放电加工过程和加工完后所表现出来的性能将直接影响冲模的使用效果。在放电加工过程中，普通硬质合金可能会出现腐蚀、表面点蚀和微裂纹等现象。为有效提高硬质合金在放电加工后的性能，美国肯纳金属公司专门研究开发出了用于精密冲模的新型硬质合金材料CD-KR887，材料采用公司独有的特殊粘结材料和粘结技术，保留了普通硬质合金的硬度和强度。与普通硬质合金相比，具有高耐电腐蚀和化学腐蚀能力和比普通硬质合金高100倍的抗腐蚀性能，[第一段]     

Effects of nano-alumina on mechanical properties and wear resistance of WC-8Co cemented carbide by spark plasma sintering

The effects of adding different nano-alumina on the structure, mechanical properties and wear resistance of WC-8Co cemented carbide during spark plasma sintering (SPS sintering) were investigated. The results show that the nano-alumina is dissolved in the Co phase, which results in a larger proportion of FCC-Co in the γ phase on the surface of the WC-Co cemented carbide. Under the scanning electron microscope, it is observed that the grains of cemented carbide are refined, and when the addition amount is 0.5 wt%, the effect of WC grain refinement is the most significan. The hardness, flexural strength and fracture toughness showed a trend of increasing first and then decreasingwith nano-alumina added. The peak value is reached when the nano-alumina content is 0.5 wt%, Which means that the alloy has the best combination of mechanical properties, that is, hardness reaches 1716 HV₃₀, bending strength reaches 2728 MPa, and fracture toughness is 12.95 MPa·m^1/2. Adding nano-alumina is beneficial to improve the wear resistance of cemented carbide. As a matter of course, when the content of nano-alumina is 0.5 wt%, the friction coefficient is the lowest, the wear rate is the smallest, and the wear resistance is the best.     

Mechanical properties of a hybrid cemented carbide composite

Microstructural effects on the mechanical properties of a hybrid metal matrix composite, double cemented (DC) carbide, have been investigated. DC carbide contains granules of WC/Co cemented carbide in a matrix of cobalt. Overall composite hardness increases with decreased granule cobalt content as well as with decreased intergranular matrix fraction of cobalt. High-stress abrasive wear resistance also increases with decreased granule cobalt content and matrix fraction. Fracture toughness of the composite increases with increased cobalt matrix fraction and to a lesser extent with increased granule cobalt content. Increased granule size increases both fracture toughness and wear resistance. DC carbide exhibits a superior combination of fracture toughness and high-stress wear resistance than conventional cemented carbide. The combination of toughness and wear resistance in the composite improves with increased granule hardness.     

矿用纳米稀土硬质合金的磨损性能研究

以石英砂为磨料,研究了YG12硬质合金的冲击磨料磨损性能与其纳米稀土添加量、硬度及断裂韧度之间的关系。结果表明,随着纳米稀土含量的增加,该硬质合金的磨损体积先减小再增大,加入1wt%纳米稀土时,其磨损量最小;随着硬度、断裂韧度的增加,合金的抗磨损性能提高。岩石颗粒的混合、粘结相的脆变和WC晶粒的破碎是矿用纳米稀土硬质合金的主要磨损机制。     

钒、钛对高铬铸铁中碳化物形态及耐磨性的影响

根据衬板工况要求，研制了加入微量V、Ti元素的高铬白口铸铁衬板。研究表明：V和Ti能使高铬铸铁组织细化，碳化物形态改善，硬度、冲击韧度和抗磨性提高。     

含Nb、W高铬铸铁溜槽衬板的研制

针对炼铁高炉布料溜槽衬板耐磨损和耐中（高）温的性能要求,对材料的化学成分、力学性能及显微组织进行了分析探讨,研制生产出含Nb、W高铬铸铁溜槽衬板,通过规范热处理,使材料硬度〉63HRC,冲击韧度aK〉24J／cm^2。与Cr20MoNi和Cr26MoNi相比,其晶粒细化,基体和共晶碳化物显微硬度明显提高,且高温组织稳定性和红硬性更好。     

Wear damage of cemented carbides with different combinations of WC mean grain size and Co content. Part I: ASTM wear tests

In the present work we made and examined cemented carbides characterized by very different WC grain sizes varying from near-nano with a WC mean grain size of about 200 nm to coarse-grain with a WC mean grain size of about 4.5 μm and Co contents varying from 3 to 24 wt.%. The major objective of the present work was to examine the wear damage, wear behavior and wear mechanisms of cemented carbides having nearly the same hardness but greatly varying with respect to their WC grain size and Co content in the high-load ASTM B611 test and low-load G65 test.Both the hardness and resistance to fracture and micro-fatigue of cemented carbides play an important role in the wear damage by use of the high-stress ASTM B611 test when the carbide surface is subjected to alumina particles at high loads. In this case, the wear-resistance increases with increasing the WC mean grain size and decreasing the Co content at nearly the same hardness of the different cemented carbides. The submicron and near-nano cemented carbides are characterized by lower wear-resistance in comparison with the coarse-grain grade due to their reduced fracture toughness, fracture resistance and resistance to micro-fatigue.The Co mean free path in the carbide microstructure plays an important role with respect to wear-resistance in the low-stress ASTM G65 test when the carbide surface is subjected to gentle scratching by abrasive silica particles. The predominant wear of the thick Co interlayers leaving unsupported WC grains plays the decisive role in the wear behavior of the coarse-grain grade resulting in its low wear-resistance. In contrast to the ASTM B611 test the wear rate decreases with decreasing the WC mean grain size and increasing the Co content due to the corresponding reduction of Co mean free path in the carbide microstructure. As a result, the wear-resistance of the near-nano grade in the ASTM G65 test is the best of all in spite of its reduced fracture toughness.Phenomena of micro-fatigue, micro-fracturing and micro-chipping are found to play a decisive role in the wear damage of cemented carbides if they are subjected to abrasion wear, high loads and severe fatigue.     

氮对低碳高铬铸铁性能的影响

通过力学性能、耐磨性能测试以及金相组织观察和ESEM形貌分析，研究了氮含量对低碳高铬铸铁性能的影响。试验结果表明，随着含氮量的增加，共晶碳化物在结晶过程中方向性生长减缓，形状趋于粒状；二次碳化物数量增加，形貌和尺寸也发生变化。随着含氮量的增加，低碳高铬铸铁的硬度增加，冲击韧度下降，滑动式和滚筒式磨损率下降。     

硬质合金复合材料

一种由硬质合金基体和硬质合金粒子制成的硬质合金复合材料。硬质合金表面均匀地分布一层高于基体硬度的粒子,这种复合材料具有表面高耐磨性,中心高韧性的特点。     

中粗WC含量对Ni-Co粗晶硬质合金微观组织及性能的影响

研究了中粗WC含量对Ni-Co粗晶硬质合金微观组织与晶粒分布的影响,进而讨论了晶粒分布对硬质合金力学性能的影响。通过金相分析了中粗WC含量对硬质合金晶粒度与邻接度的影响,并利用截线法研究了微观组织的晶粒的分布规律;研究了晶粒度与晶粒分布对磁力、密度及其它力学性能的影响。结果显示,中粗WC晶粒可均匀分布在粗晶WC周围阻碍粗晶与粘结相接触,抑制了粗晶粒的快速粗化,降低了合金平均晶粒度与平均自由程,使晶粒分布逐渐转变为双峰分布;在压力烧结下所有合金的相对密度均在99.5%以上,通过对矫顽磁力的测试分析,验证了微观组织中晶粒双峰分布的准确性;平均晶粒度的降低使合金硬度逐渐增加、断裂韧性逐渐降低;微观组织中超粗晶粒逐渐减少,有利于硬质合金抗弯强度与耐磨性的提高。在Ni-Co粗晶硬质合金中加入部分中粗WC颗粒有利于减少晶粒粗化进而提高耐磨性,加入30%中粗WC颗粒时综合性能最好。     

Fracture toughness of cemented carbides obtained by electrical resistance sintering

The unique combination of hardness, toughness and wear resistance exhibited by WC-Co cemented carbides (hardmetals) has made them a preeminent material choice for extremely demanding applications, such as metal cutting/forming tools or mining bits, in which improved and consistent performance together with high reliability are required. The high fracture toughness values exhibited by hardmetals are mainly due to ductile ligament bridging and crack deflection (intrinsic to carbides). In this work two WC-Co grades obtained by using the electric resistance sintering technique are studied. The relationships between the process parameters (cobalt volume fraction, sintering current and time, die materials, etc.), the microstructural characteristics (porosity, cobalt volume fraction, carbide grain size, binder thickness and carbide contiguity) and mechanical properties (Vickers hardness and fracture toughness) are established and discussed. Also the presence of microstructural anisotropy and residual stresses is studied. The sintering process at 7 kA, 600 ms and 100 MPa, in an alumina die, followed by a treatment of residual stress relief (800 °C, 2 h in high vacuum), allows to obtain WC-Co pellets with the best balance between an homogeneous microstructure and mechanical behaviour.