金刚石含量对金刚石强化硬质合金耐磨性影响

随着采矿和城市基建等行业的发展,对硬质合金的耐磨性提出了更高的要求。通过添加金刚石增强硬质合金的耐磨性是一种可行的新思路。本研究采用放电等离子体烧结技术（SPS）制备了金刚石体积分数为0～15%金刚石增强硬质合金,分析了合金中金刚石石墨化程度并采用砂轮法研究了材料的磨损性能。结果表明：该条件制备的硬质合金中金刚石均未转变为石墨;金刚石可以增强硬质合金的韧性;硬质合金的磨损系数K随着金刚石含量的增加先增加后降低。金刚石颗粒之间的距离减小会导致基体对金刚石颗粒的把持力降低,使金刚石颗粒易脱落且金刚石脱落形成的脱落坑也将作为缺陷降低合金的耐磨性。     

WC/Co粉体粒径匹配与放电等离子烧结致密化

对放电等离子烧结(SPS)不同粒径匹配的WC/Co混合粉末的收缩过程进行了系统分析.结果表明,SPS烧结不同WC粒径混合粉末时,烧结体开始收缩温度、收缩速率峰值温度和致密化完成温度基本相同;对不同Co粒径混合粉末,三种温度随Co粉初始粒径的减小而降低,即SPS烧结过程与WC粒径无关而与Co粒径密切相关.SPS致密化过程中收缩速率随温度的变化、收缩速率与相对密度的关系均与常规烧结不同,其开始收缩温度和收缩速率峰值温度均较常规烧结低,同时收缩速率峰值处所对应的相对密度也较常规烧结低.这说明在常规烧结中粉末在大量液相出现(即收缩速率出现峰值时)之前已完成很大程度的收缩致密化,而SPS烧结中大量液相出现之前粉末的收缩致密化程度较低.     

Co对弧光放电离子镀WC—Co膜生长的影响

利用弧光放电离子镀法获得了难熔超硬ＷＣ－Ｃｏ膜。随着Ｃｏ含量的增加，使真空室里等离子态趋于稳定，并使成膜速度增加；其组织结构为Ｔｈｏｒｎｔｏｎ图里的Ｔ区，并逐渐由柱状晶组织变成致密的组织结构。     

烧结工艺对纳米WC/MgO复合材料性能的影响

利用高能球磨法和放电等离子烧结技术制备了纳米WC/MgO复合材料,研究了烧结温度和烧结压力对WC-8wt%MgO复合材料密度、硬度和断裂韧性的影响.结果表明,烧结温度过低,试样的致密度差;烧结温度过高,晶粒快速长大,使得复合材料性能降低;烧结压力越大,复合材料的致密度越高,硬度和断裂韧性越好.最佳烧结工艺是烧结温度1650℃,烧结压力70 MPa,获得了该复合块体材料的最佳性能组合.     

亚微米WC添加对超音速火焰喷涂WC–Co涂层磨损性能影响

采用湿法球磨将亚微米WC（~300 nm）和WC–12Co粉末混合均匀并使亚微米WC均匀粘附于WC–12Co粉末的表面,采用超音速火焰喷涂方法（HVOF）在304不锈钢基体表面制备WC和WC–12Co的WC–Co复合涂层,研究亚微米WC的添加对涂层相组成、显微硬度、耐磨性能和表面形貌的影响。利用X射线衍射分析涂层相组成,压痕法测试涂层的显微硬度,通过往复式摩擦磨损实验测试磨损性能,扫描电子显微镜（SEM）对涂层磨损表面和断面进行微观形貌观察,并分析涂层的磨损过程和机制。结果表明,添加质量分数5%的亚微米WC颗粒显著提高了涂层的显微硬度（16.3%）;增强了涂层的耐磨性,磨损率从6.09×10-7 mm3/Nm减小到5.15×10-7 mm3/Nm（减小13.8%）;亚微米WC颗粒喷涂后在涂层中保持了WC相,并主要存在于WC–Co扁平粒子界面和孔隙。基于涂层中扁平粒子的结合特性与磨损失效特征,建立强化模型,分析亚微米WC颗粒对涂层扁平粒子界面的强化机制。     

Co对弧光放电离子镀WC－Co膜生长的影响

利用弧光放电离子镀法获得了难熔超硬ＷＣ－Ｃｏ膜（其中含Ｃｏ为０，４，１５ｗｔ－％）．随着Ｃｏ含量的增加，使真空室里等离子态趋于稳定，并使成膜速度增加；其组织结构为Ｔｈｏｒｎｔｏｎ图里的Ｔ区，并逐渐由柱状晶组织变成致密的组织结构。     

烧结温度对Ti2SnC/TiC复合材料摩擦磨损特性的影响

以Ti、Sn和C的单质粉体为原料,通过放电等离子烧结技术合成Ti2SnC和TiC的复合材料.研究烧结温度对Ti2SnC/TiC复合材料组织和摩擦磨损等性能的影响.结果表明,烧结温度低于700℃时,烧结块体主要由Ti6Sn5相组成;烧结温度升高到900～1000℃时相组成变为Ti2 SnC+ TiC;当温度高于1000℃时Ti2SnC有分解迹象.1000℃烧结的复合材料具有较低的硬度和较小的摩擦因数.     

真空热压烧结对Cu/WC复合材料性能的影响

采用粉末冶金真空热压烧结法制备Cu/WC复合材料,研究了WC含量及材料烧结时间对硬度及导电等件能的影响.结果表明,真空热压烧结可明显改善WC颗粒度分布,提高复合材料的致密度、硬度和导电性;v(WC)=1.5%、烧结时间为3 h时,材料的综合性能最好.     

WC/17Co含量对Ni基喷焊涂层性能的影响

将不同比例的WC/17Co与Ni60粉末进行混合,并采用氧乙炔火焰喷焊工艺制备了相应的涂层。分别用洛式硬度计和X衍射仪测试了各涂层的硬度和相结构;采用湿砂橡胶轮式磨粒磨损实验机对各涂层的抗磨粒磨损性能进行了测试,采用扫描电镜观察了喷焊粉末形貌和喷焊层的磨损形貌,并进行了能谱分析。结果表明,喷焊层的组织为在γ-Ni固溶体基体上弥散分布着细小的Cr7C3、Cr23C6、Cr2B、CrB2和WC等硬质相。喷焊层的硬度随WC/17Co添加量的增加先增加后减小,当WC的含量为25wt%时,喷焊涂层的硬度最高,相应的抗磨粒磨损性能最好。     

WC粒度对WC/10Co注射成形工艺的影响

研究了不同粒度的WC粉末对WC/10Co注射成形工艺(PIM)的影响,分析了WC粒度对喂料流变性、注射坯质量、脱脂工艺和烧结工艺的影响机理。结果表明:WC粒度越小,WC/10Co喂料流变性越差,注射坯质量越低,溶剂脱脂速率越高,合金形状偏差越大。超细WC/10Co喂料存在粉末团聚颗粒、粘结剂包裹不充分,其热稳定性低、流动性降低56%,注射坯致密度下降5%;超细WC-10Co合金的线收缩率达到20.80%,尺寸偏差为2.85%,脱脂-真空烧结时易出现脱碳现象。     

Tailored sintering of VC-doped WC–Co cemented carbides by pulsed electric current sintering

WC–12 wt.% Co powder mixtures with 0, 0.45 or 0.9 wt.% VC additions were consolidated by solid state pulsed electric current sintering (PECS) for 2 min at 1080–1240 °C. The influence of the sintering condition and VC concentration on the densification, WC grain growth and mechanical properties of the cemented carbides were investigated. Finite element simulation revealed that the radial temperature gradient inside the sintering powder compacts could be homogenised using a carbon felt insulation surrounding the graphite die set-up.     

富Ce混合稀土对铝基混杂复合材料耐磨性能的影响

用挤压铸造法制备Al2O3短纤维石墨颗粒混杂增强ZL109复合材料,并研究富Ce混合稀土对该混杂复合材料耐磨性能的影响。结果表明:适量稀土元素可在一定程度上改善该混杂复合材料的耐磨性能,特别在低载荷下,其作用更为显著;稀土对复合材料磨损机制的影响与载荷有关,在较低的载荷下,犁沟磨损是复合材料的主要磨损机制,并存在轻微的剥层破坏;但在较大载荷下,稀土元素加入后,特别是稀土含量高于0.6%后,复合材料的磨损机制由犁沟磨损转变为严重的剥落磨损,复合材料耐磨性反而降低,这可能与稀土含量高时富含稀土的针状相析出有关。     

The effect of boron-pack refreshment on the boriding of mild steel by the spark plasma sintering (SPS) process

Mild steel samples were borided with and without boron pack refreshment using the spark plasma sintering (SPS) process. Results show that the borided samples with boron pack refreshment developed a thicker boride layer compared to that without boron pack refreshment for the same boriding duration. When boriding duration is t < 120 min, the boriding growth in the samples borided with boron pack refreshment followed a parabolic growth pattern. In contrast, the boride growth in samples processed without boron-pack refreshment deviates from parabolic at t = 60 min. Computer simulation shows that the boron concentration change in the boriding media during the boriding process is an important factor affecting the composition and final thickness of the boride layer.     

WC对铁基合金喷焊层组织及磨损性能的影响

采用等离子喷焊技术在Q235表面制备铁基合金喷焊层,借助X射线衍射分析、金相显微镜以及摩擦磨损实验,研究一定含量的WC对铁基合金喷焊层组织及磨损性能的影响。结果表明:铁基合金喷焊层主要由α-Fe,γ-Fe,(Fe,Cr)_7C_3和(Fe,Ni)固溶体等物相组成,加入WC后,出现了(Fe,Cr)_(23)C_6,WC,W_2C等新物相。未加入WC的喷焊层出现了疲劳剥落,数量较多、较深且平直的犁沟,表现为粘着磨损和磨料磨损;加入WC后疲劳剥落减弱,犁沟减少,表现为磨料磨损。喷焊层中硬质相的弥散强化作用提高了硬度和耐磨性。     

用SPS技术制备La-g-i储氢合金的工艺探究

采用放电等离子烧结技术（SPS）制备La-Mg-Ni储氢合金，以La0.7Mg0．3Ni2.5Co0.5合金为例，探究最佳的工艺制度。结果表明：当烧结温度为800℃时，合金为多相结构，包括（La，Mg）Ni3相、（La，Mg）2Ni7相、Mg2Ni相和微量的Co2Mg相；在该温度下，合金的最大放电容量达到最大值359mAh／g，同时表现出最好的放电平台特性。     

放电等离子烧结TiB/Ti-1.5Fe-2.25Mo复合材料的微观组织与力学性能

采用放电等离子烧结技术原位合成了TiB增强Ti?1.5Fe?2.25Mo复合材料,研究了烧结温度对复合材料微观组织和力学性能的影响规律。结果表明,随着烧结温度的升高,钛合金中 TiB 晶须的长细比迅速减小;然而,复合材料的相对密度及TiB的体积含量随着烧结温度的升高而不断增大。由于TiB晶须长细比的减小会导致复合材料强度的降低,而复合材料的相对密度及TiB体积含量的增大又会带来复合材料强度的增加,因此,在这两种因素的共同作用下,最终导致 TiB/Ti?1.5Fe?2.25Mo复合材料的弯曲强度随着烧结温度的升高而缓慢增大。在烧结温度为1150°C 时,TiB/Ti?1.5Fe?2.25Mo复合材料具有最大的弯曲强度1596 MPa。     

放电等离子烧结TiAl-V-Cr合金的拉伸和压缩性能

以Ti-47.5Al-2.5V-1.0Cr合金粉末为原料,采用放电等离子烧结工艺制备出TiAl基合金,并研究了显微组织对合金的室温拉伸、压缩性能以及断裂机制的影响。结果表明,采用SPS方法可制备组织成分均匀的TiAl-V-Cr合金材料,其室温拉伸、压缩性能以及断裂机制与显微组织类型和晶粒尺度密切相关,且对于相同组织的合金,其压缩性能远远优于拉伸性能。当烧结温度为1100℃时,具有细小双态组织的合金具有最佳的室温力学性能,其抗压强度为3321 MPa,压缩率为35.2%。     

Microstructures and mechanical properties of the in situ TiB-Ti metal-matrix composites synthesized by spark plasma sintering process

In situ synthesized TiB reinforced titanium matrix composites have been synthesized by spark plasma sintering (SPS) process at 950-1250 °C, using mixtures of 15 wt% TiB₂ and 85 wt% Ti powders. The effects of the sintering temperature on densification behavior and mechanical properties of the TiB-Ti composites were investigated. The results indicated that with rising sintering temperatures, relative densities of the composites increase obviously, while the in situ TiB whiskers grow rapidly. As a result, bending strength of the TiB-Ti composites increases slowly at the combined actions of the factors referred above. Fracture toughness of the composites is improved remarkably due to the large volume fraction of Ti matrix, the crack deflection, pull-out and the micro-fracture of the needle-shaped TiB grains. The results also suggested that TiB-Ti composite sintered at 1250 °C by SPS process exhibits the highest relative density of 99.6% along with bending strength of 1161 MPa and fracture toughness of 13.5 MPa m^1/2.     

Effect of porosity on wear resistance of SiCp/Cu composites prepared by pressureless infiltration

The influence of porosity on the wear behavior of high volume fraction （61%） SiCp/Cu composite produced by pressureless infiltration was studied using a sliding, reciprocating and vibrating（SRV） machine. SiCp/Cu composites slid against hardened GCr15 bearing steel ball in the load range of 40-200 N. The results show that the wear rate increases with increasing porosity. The composite containing low porosity shows excellent wear resistance, which is attributed to the presence of mechanically mixed layer on the worn surface. In this case, the dominant wear mechanism is oxidative wear. Comparatively, the composite containing high porosity exhibits inferior wear resistance. Fracture and spalling of the particles are considered as the main causes of severe wear. Third body abrasion is the controlling wear mechanism. In addition, porosity has more important influence on wear rate at high load than at low load. This is associated with the fact that the fracture and spalling of particles is a process of crack initiation and propagation. At lower load, the pores beneath the worn surface can not propagate significantly, while the pores become unstable and easily propagate under high load, which results in a higher wear rate.     

Spark Plasma Sintering of Ultrafine YSZ Reinforced Cu Matrix Functionally Graded Composite

Copper matrix composites have received more attentions as possible candidate for thermal and electrical conductive materials to be used in electrical contact applications. In this study, five-layered Cu/YSZ(yttria-stabilized zirconia) functionally graded material(FGM) and copper matrix composite specimens containing 3 and 5 vol% YSZ particles plus pure Cu specimen were synthesized using powder metallurgy(PM) route and spark plasma sintering(SPS)consolidation process. The microstructural and some physical, mechanical features of all specimens were characterized.Microscopic examinations showed that ultrafine YSZ particles were distributed in the copper matrix almost homogeneously. An appropriate interface was observed at each layer of FGM. The density measurement indicated that the graded structure of the composite could be well densified after the SPS process. The microhardness values of various layers of Cu/YSZ FGM specimen were gradually altered from 56.3(pure copper side) to 75.2 HV(Cu-5 vol% YSZ side). The increase of YSZ content resulted in a decrease in electrical conductivity. Additionally, thermal conductivity of Cu/YSZ FGM specimen [308.0 W/(m K)] was determined to be higher than that of the Cu-5 vol% YSZ composite specimen [260.7 W/(m K)]. Accordingly, it can be concluded that the Cu/YSZ FGM can be a good candidate for the electrical applications, like sliding electrical contacts, where different material characteristics in the same component are required.