真空二次热压及复压复烧对铜/金刚石复合材料致密度的影响

采用真空二次热压和复压复烧烧结技术制备了铜/金刚石复合材料,研究并讨论了烧结方法和混粉工艺以及金刚石颗粒尺寸和体积分数对该复合材料致密度和微观形貌的影响.结果表明,真空热压烧结的复合材料致密度优于复压复烧,且二次热压对其致密度有明显改善,其中金刚石分数40vol％,粒度90μm的铜/金刚石复合材料的致密度最高,达到了98.45％.     

金刚石工具专用FeCo合金的研究

本文采用湿法冶金的方式制备铁钴合金Fe80Co20,通过工艺试验、替代试验、切割试验及添加试验进行热压及应用性能研究。研究结果表明：Fe80Co20本身即具有良好的热压性能,替代同比例的Co粉以后,烧结温度普遍降低,硬度略有降低,抗弯强度有不同程度提高,由切割试验及添加试验可以看出Fe80Co20合金与预配粉相比有更好的金刚石把持力,更好的综合性能。     

Cu2O基金属陶瓷热压制备及其致密化过程

研究了混粉工艺、烧结温度以及热压压力对金属陶瓷微观组织的影响,并探讨了Cu2O基金属陶瓷的热压烧结致密化机理.结果表明:以枝状Cu粉制备的金属陶瓷中Cu颗粒呈蠕虫状形貌,采用两步法混粉工艺可制备含有球形Cu颗粒的金属陶瓷;烧结温度和热压压力的增加都会提高金属陶瓷的相对密度,但其影响程度不同;金属陶瓷的热压烧结致密化机理为颗粒在外力作用下的塑性流动和粒子重排.     

Co含量对金刚石–WC–Co复合材料耐磨性的影响

随着采矿和城市基建等行业的发展,对矿用WC–Co采掘工具的耐磨性提出了更高的要求。通过添加金刚石增强WC–Co矿用工具的耐磨性是一种可行的新思路。在烧结制备金刚石–WC–Co复合材料的过程中钴相作为催化剂会加速金刚石向石墨转变。为研究Co对复合材料中金刚石石墨化程度的影响,采用放电等离子体烧结技术(SPS)制备金刚石–WC–Co复合材料,分析了复合材料中金刚石石墨化程度并采用砂轮法研究了复合材料的磨损性能和磨损机理。结果表明：金刚石–WC–Co复合材料中金刚石可以起到增韧效果;Co含量增加会促进复合材料致密化进程,同时也会降低复合材料的硬度;随着Co含量增加,复合材料材料耐磨性变差。磨损过程中 WC–Co基体率先被磨损去除,金刚石后被磨损,金刚石会增强材料的耐磨性能。     

稀土在以Fe代Co金刚石工具材料中的应用

本文将以Fe代Co的金刚石工具（胎体）材料作为重点研究对象,借鉴了稀土在硬质合金中应用的工艺经验,主要以掺杂法添加稀土La或Ce,对添加方式,添加形态及添加量进行了改进和优化,同时还在工艺过程中用TiH2进行了还原处理,确定了较佳的TiH2还原处理工艺路线,测试了金刚石工具（胎体）材料的实际使用性能,证实了在金刚石工具（胎体）材料中以Fe代Co,并通过添加稀土元素来提高Fe基金刚石工具材料的实际使用性能是完全可行的。     

孕镶金刚石工具用Fe—Cu粉末胎体材料的性能研究

金刚石的大幅度降价,以及金刚石镀膜技术的发展,大力促进了廉价材料（例如铁）的应用（除活性胎体材料外）。目前,正在使用具有优良烧结性能、良好的机械性能和类似钴的现场切割性能的廉价材料替代昂贵的钴基材料。本论文作者的主要目的是,建立预合金粉末的成分和固结条件对用作孕镶金刚石工具胎体的铁基以及不含钴的材料微观结构和机械性能的影响。用预合金Fe—Cu粉末和Fe—Cu—Sn—Sm2O3粉末作为实验原材料,采用热压和先冷彤后烧结两种粉末的固结工艺路线,经固结的全部试样都进行了密度测定和洛氏硬度试验,还检测了热压试样的抗弯性能和用扫描电子显微照片以及X射线衍射对其进行了检测,这两种预合金粉末都表现出优良的致密化性能。     

铜磷预合金粉在金刚石工具中的应用

在金刚石工具中添加铜磷预合金粉,热压烧结过程中铜磷预合金粉瞬时液化对铁铜基础粉形成钎焊连接,烧结体的致密度、硬度、强度均得到提高。铜磷预合金粉改善单质铁粉和铜粉的润湿性和结合力,并在晶界处生成脆性化合物,增加烧结体的脆性,提高了金刚石工具的锋利度,在金刚石工具行业中具有广阔的应用前景。      

W-Ni-Fe高比重合金液相烧结时的致密化

研究了W-Ni-Fe高比重合金烧结时的致密化,实验证明W-Ni-Fe合金烧结时的致密化过程具有液相烧结的特征,符合Kjngery提出的方程。目前生产的W-Ni-Fe合金中粘结相常采用Nj:Fe=7:3或Ni:Fe=1:1。针对这两种成分的合金我们研究了不同温度下的收缩率、密度变化与时间的关系,并讨论了其致密化机理。     

Fe_3Al基摩擦材料的烧结致密化过程研究

利用热压烧结方法制备了以Fe3Al金属间化合物为基体,以Cu、石墨、MoS2、Al2O3为添加剂的一种复合摩擦材料,并对其烧结致密化过程以及影响因素进行了试验研究。结果表明,材料的致密化过程受到原始粉料组成、粒度以及烧结工艺参数(如烧结温度、压力、保温时间)等多种因素的共同影响,其中Cu的液相烧结在材料致密化过程中起到重要作用。最佳工艺参数为:烧结温度1 050￣1 100℃,压力10￣12 MPa,保压20￣30 min,保温45￣60 min,此时致密度为90%￣95%。烧结过程中未发现晶粒异常长大,经1 050℃烧结1 h的摩擦材料中Fe3Al的晶粒尺寸为400￣600 nm。     

Y2O3对铁基金刚石工具性能的影响

采用正交试验方法研究热压压力、烧结温度和Y₂O₃含量等3个因素对铁基胎体硬度、致密度、抗弯强度和断口微观形貌等的影响,并获得较优的烧结工艺参数。在此基础上,制备含Y₂O₃的铁基金刚石工具,并对其断口形貌、耐磨性和锋利度等进行检测及分析。结果表明:含Y₂O₃的铁基结合剂胎体,其相对密度和硬度的影响因素次序为Y₂O₃含量＞烧结温度＞热压压力,抗弯强度的影响因素次序为烧结温度＞Y₂O₃含量＞热压压力;且Y₂O₃能促进铁基金刚石胎体组织的致密化,降低其烧结温度。在烧结温度为780 ℃、热压压力为51 kN的较优烧结工艺下,适量的Y₂O₃能使金刚石工具的孔隙率减小、黏结状况改善,并增强黏结剂对金刚石磨粒的把持能力。      

Influence of B4C coating on graphitization for diamond/WC-Fe-Ni composite

Diamond/WC-Fe-Ni composite is a potential composition for impregnated diamond drill bits. It is necessary to avoid the graphitization of the diamond from Fe and Ni under the powder metallurgy process. Boron carbide (B₄C) was coated on diamond, and diamond/WC-Fe-Ni composites were consolidated by hot pressing at different temperatures. The influences of sintering temperature and interfacial structure on bending strength and wear behavior were investigated. The bending strength for diamond/WC-Fe-Ni composite was dependent on matrix densification and interfacial graphitization. Un-coated diamond was eroded by Fe-Ni matrix and partially converted to graphite during the sintering process at all sintering temperatures. In opposite, B₄C coating was beneficial to matrix densification at a lower sintering temperature, and delayed the appearance of graphitization to around 1300 °C. Therefore, the diamond/WC-Fe-Ni composites with B₄C coating exhibited larger bending strength and better wear behavior at a relative low sintering temperature.     

热等静压技术对金刚石工具制品性能的影响

采用热等静压和传统热压两种烧结方式对Co粉进行烧结,研究两种烧结工艺所得制品在密度、硬度、抗冲击强度、抗弯强度等力学性能以及锯切性能上的差异。结果表明:相比传统热压烧结而言,采用热等静压烧结制备的金属胎体,在相对密度、抗冲击强度、抗弯强度、锯切性能方面都有明显提升;采用热等静压工艺烧结的制品,其硬度较传统热压烧结的制品的略低。利用热等静压烧结制备的金刚石绳锯产品,在锯切试验中表现出良好的性能。      

Rapid discharge sintering of nickel-diamond metal matrix composites

In this study rapid discharge sintering (RDS) and furnace sintering of nickel-diamond metal matrix composites (MMCs) is compared. Nickel-diamond powder composites (80-20% by weight respectively) were uniaxially pressed into 20 mm discs at compaction pressures of 100, 200 and 300 MPa. Discharge sintering was carried out using a microwave plasma formed with hydrogen and hydrogen/nitrogen as the discharge gases and tube furnace sintering carried out in a argon or a hydrogen/nitrogen (3:1) atmosphere. Discs pressed to 300 MPa were treated at both 850 and 1000 °C. The properties of the sintered nickel-diamond composites were characterized using density, approximate flexural strength, hardness, wear resistance, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The RDS samples sintered at 1000 °C achieved the maximum approximate disc flexural strength of 473 MPa within a 20 min treatment time compared with 6 h for furnace sintered samples. Samples sintered using the RDS technique exhibited increased hardness values and a finer nickel matrix over furnace sintered samples. Using the RDS technique it has been possible to process nickel-diamond MMCs without oxidation or graphitisation at temperatures above 900 °C. Minimal diamond destruction was observed during abrasive wear testing of the RDS samples compared with damage and pull-out observed for furnace sintering.     

Temperature dependence of microstructure evolution during hot pressing of ZrB2–30 vol.% SiC composites

Microstructure evolutions of ZrB₂–30 vol.% SiC composites, prepared by hot pressing at different processing temperatures (1700, 1850 and 2000 °C) for 30 min under 10 MPa, were investigated by optical microscopy, scanning electron microscopy and transmission electron microscopy (TEM). The microstructures of the fabricated composites were compared with and the effects of the processing temperature on the sintering process and densification behavior during the hot pressing were found. The amount and the orientation of dislocations which were indicated by TEM analysis in the sample hot pressed at 1700 °C showed that no plastic deformation and atomic diffusion occurred. But the presence of amorphous phases and rearrangement of particles are signs of the fact that liquid phase sintering and particle fragmentation/rearrangement is the main densification mechanism. On the other hand, in the sample hot pressed at 1850 °C, aggregation of dislocations behind the grain boundaries and the presence of twinnings addressed wide plastic deformations which were introduced as the main densification mechanism at 1850 °C. Finally in the sample hot pressed at 2000 °C, lower amounts of un-oriented dislocations and also some annealing twinnings were observed in TEM micrographs together with fractographical SEM analysis and showed that the atomic diffusion is the dominant densification mechanism of hot pressed ZrB₂–30 vol.% SiC composite.     

添加La2O3对激光烧结(WC-Co)p/Cu金属基复合材料组织和成形性能的影响

研究了稀土氧化物La2O3添加量对激光烧结直接成形(WC-10Co)颗粒增强Cu基复合材料的影响.结果表明,优化La2O3含量(1.0%),可细化激光烧结组织,提高增强颗粒分散均匀性以及颗粒/基体界面结合性能,成形致密度高达理论密度的96.3%,显微硬度HV可达403.1;而过量添加La2O3(≥1.5%),导致激光成形性能降低.讨论了稀土原子对颗粒增强金属基复合材料激光烧结成形的作用机理.     

Influence of WC addition on the microstructure and mechanical properties of NbC–Co cermets

NbC–24.5 wt.% Co cermets with up to 30 wt.% WC were obtained by solid state hot pressing at 1300 °C under a pressure of 45 MPa for 10 min and pressureless liquid phase sintering at 1360 °C for 60 min. The effect of WC addition on the microstructure and mechanical properties of NbC–Co based cermets was investigated. The hot pressed cermets exhibited interconnected and irregular niobium carbide (NbC) or (Nb,W)C grains, whereas the shape of the NbC grains changed from faceted with rounded corners to spherical, as the WC content increased in the pressureless sintered cermets. The undissolved WC increased with increasing WC addition. A clear core/rim structure was observed in the hot pressed cermets with 10–30 wt.% WC additions, whereas this structure was gradually eliminated when pressureless sintering. The hardness remains nearly constant whereas the fracture toughness slightly increases with increasing WC addition. The dissolution of WC in the Co binder and NbC grains, as well as the formation of a solid solution (Nb,W)C phase were supported by thermodynamic calculations.     

粉末冶金TiAl合金排气门的研制

利用元素粉末冶金方法制备了TiAl合金排气阀。为提高排气门杆部的致密度、均匀度 ,设计了特有的径向热压工艺 ,并从理论上分析了与该工艺相关的压坯密度、致密化和应力变化规律。制备出高径比为 10 .7,密度为 3.79g/cm3 的粉末冶金TiAl合金汽车发动机排气门     

快淬带粉末冶金法制备块状La(Fe, Co, Si)13磁制冷材料

利用快淬带粉末通过常压烧结技术制备了块状La(Fe,Co,Si)13磁制冷材料,并研究了温度和烧结助剂LaFeSi对烧结体显微组织与性能的影响。研究表明:随着烧结温度的提高,烧结体的密度增加,相成分发生明显的变化,具有立方NaZn13型La(Fe,Co,Si)13相大量生成。当向快淬带LaFe10.8Co0.7Si1.5C0.2粉末添加20%LaFeSi粉末经压样成形后在1200℃烧结3 h后,得到的烧结体基本是单一的La(Fe,Co,Si)13相,致密度达到90%左右。