镍基合金—碳化铬复合涂层抗磨损性能的研究

为了得到耐磨损的表面涂层,用真空熔烧方法制成与钢基休牢固结合的镍基自熔合金—碳化铬复合涂层。用扫描电子显微镜及X射线衍射仪对涂层的组织和结构进行了观察和分析。应用环块磨损试验机,对具有不同碳化铬含量的镍基复合涂层对金属的摩擦副进行了磨损试验。试验结果指出,在同样条件下,在涂层对金属副中的复合涂层的磨损抗力比在金属对金属副中的GCr15钢要好。复合涂层的磨损率比GCr15钢及纯镍基合金涂层降低约一个数量级,并且复合涂层的磨损率是随碳化铬含量增加而下降的。根据试验结果,对在复合涂层中合理的碳化铬含量也进行了讨论。     

0.3C-Cr-W渗氮轴承钢的微动摩擦磨损性能

利用SRV-4高温摩擦磨损试验机对0.3C-Cr-W高性能渗氮轴承钢进行了微动磨损试验,分别改变载荷和频率,研究了表面离子渗氮对摩擦磨损性能的影响.结果表明:试验钢表面渗氮后渗层厚度为238.45 μm,其中白亮的化合物层厚度为9μm,主要为γ'-Fe4N和VN两种相;渗氮后试样表面的白亮化合物层具有减小摩擦因数和提高耐磨性的作用;渗氮前后试验钢的磨损机制相同,前期以粘着磨损为主,以磨粒磨损为辅;磨损后期转变为以磨粒磨损为主,以粘着磨损为辅;渗氮前试验钢的磨损体积是渗氮后的3倍以上,表面离子渗氮后试验钢的抗微动磨损性能有明显的提高.     

Ni/Ni_3Al两相合金箔材的退火行为研究

研究了冷轧变形95%的Ni/Ni3Al两相合金箔材在经过100h退火后的再结晶过程以及织构和晶粒的微取向的变化。对其织构的测量未表现出如冷轧单相Ni3Al合金退火后所具有的织构记忆效应。EBSD(electron back-scattered diffraction)的测量结果显示退火后根据晶粒的取向可分为两个区域,一个区域的晶粒保持了与冷轧后试样的晶粒相同的取向,即其取向为(110),并且这一区域沿轧制方向呈带状分布,而另一个区域的晶粒的取向则为随机的。两个区域中(110)取向晶粒所占的百分比依次为57%和16%,并且在长时间退火后这种带状结构依然存在。冷轧变形95%的Ni/Ni3Al两相合金箔材在600～800℃之间退火时存在两种再结晶过程。一部分区域退火后生成大量的晶粒取向随机分布的再结晶晶粒,而在另一部分区域则其再结晶晶粒保持与冷轧织构相同的晶粒取向,并随着退火温度的升高而长大。     

多孔预制件对TiC/Ni_3Al复合材料孔隙率的影响

采用无压熔渗法制备了TiC含量较高的TiC/Ni3Al复合材料,分析了不同TiC质量分数对多孔预制件孔隙率的影响,利用无压浸渗多孔体理论分析了多孔预制件孔隙结构对复合材料孔隙率的影响.结果表明:通过增加TiC质量分数可以调节多孔预制件的孔隙结构,使预制件的孔隙率增加;多孔预制件孔隙结构的变化可以调节复合材料的孔隙率.多孔预制件的孔隙率越高、孔隙尺寸越大,则金属间化合物熔体浸渗畅通,复合材料的孔隙率越小.     

Mo_5Si_3-Al_2O_3复合材料的微观结构与摩擦磨损性能

采用机械化学还原法结合热压烧结制备Mo_5Si_3-Al_2O_3复合材料,采用XRD、SEM等对复合材料的相组成、微观结构及磨损机理进行分析。结果表明:复合材料主要物相为Mo_5Si_3、Al_2O_3和Mo_3Si,其组织均匀细小,晶粒尺寸在1~5μm之间。Mo_5Si_3-Al_2O_3复合材料具有优异的抗摩擦磨损性能。随载荷增加,其摩擦因数和磨损率降低。载荷为10 N时,其摩擦因数和磨损率分别为0.176和6.23×10~(–6) mm~3/(N·m)。与对磨件GCr15钢球相比,其磨损率降低近1个数量级。Mo_5Si_3-Al_2O_3复合材料主要的磨损机理为氧化磨损和从低载荷下的粘着-剥落磨损过渡到高载荷下的磨粒磨损。     

Ni_3Al金属间化合物的研究进展

Ni3Al金属间化合物因具有熔点高、抗蠕变强度大、密度低、耐腐蚀、耐氧化以及其它优异性能,已被广泛应用于航空、冶金、机械、电化学、环保工业等领域,并有进一步发展的潜力和扩大应用的需求.该文对Ni3Al金属间化合物的制备及性能的研究进展进行综合评述,并着重论述粉末冶金法制备Ni3Al金属间化合物及其产品的抗氧化与催化性能等的研究现状.     

超音速等离子喷涂NiCr-Cr_3C_2涂层的组织结构与微动磨损性能

采用超音速等离子喷涂法在1045钢表面制备NiCr-Cr_3C_2涂层,分析涂层的微观结构及化学成分以及涂层的晶粒结构,利用MICROMET-6030显微硬度仪和Nano-test 600纳米压痕仪测定涂层的显微硬度与弹性模量,通过油润滑微动摩擦磨损试验测试涂层的微动磨损性能。结果表明,NiCr-Cr_3C_2涂层为明显的层状结构,具有单晶、纳米多晶与过渡区共存的复杂晶体学结构,显微硬度HV0.3高达998,约为基体材料硬度的3倍,弹性模量为224.6GPa;涂层的微动摩擦因数随载荷增大而减小,随温度升高而增大。喷涂层的抗微动摩擦磨损性能较基体优异,摩擦因数及体积磨损量分别比基体降低36.7%和55.6%。涂层的磨损机理以磨粒磨损和疲劳剥落为主。     

Ni3Al基合金堆焊层开裂的研究

本文结合Ｎｉ３Ｎｌ基合金堆焊熔池凝固过程中的相变分析和堆焊层中的热应力分析，研究了电弧堆焊条件下Ｎｉ３Ａｌ基合金堆焊层中热裂纹产生的原因。分析表明，当电弧堆焊速度比较高时，由于堆焊熔池中液相快速冷却而发生非平衡相变，使所析出的富Ｎｉ枝晶ｒ相间的富Ａｌ液相最后发生共晶反应，而生成γ相和β′相片层组织。另外，高的堆焊速度堆焊层中产生高的热应力，当堆焊层中局部热应力超过γ′相和β′相的内聚强度时，产生枝     

一种含铁Ni_3Al基合金的热变形行为

采用Gleeble-1500D热模拟试验机对一种含铁Ni3Al基合金进行了高温压缩试验,试验温度为1 050~1 150℃,应变速率为0.1~1.0s-1,工程应变量为50%。获得了不同变形条件下的真应力-真应变曲线,并分析了合金微观组织的变化。结果表明:合金的流变应力随着变形程度的增加先达到峰值应力,之后逐渐降低,趋于稳态流变。提高变形温度及减小应变速率能有效促进动态再结晶过程。在变形温度1 100℃以上,工程应变为50%时,能够获得完全再结晶的锻态组织。基体中的γ′相粒子对合金动态再结晶有抑制作用,β相的存在促进了相界处动态再结晶形核但抑制了完全动态再结晶晶粒的长大。高温下β相的软化效应和γ′相的回溶转变都有效提高了Ni3Al基合金热加工性能。     

有序金属间化合物Ni_3Al

本文主要根据美国 Oak Ridge 国家实验室 C.T.Lia 教授的科学报告,并结合作者在美期间的部份工作,重点介绍了金属间化合物 Ni_3Al 的研究工作和结果。     

Abrasive Performance of Chromium Carbide Reinforced Ni3Al Matrix Composite Cladding

The Microstructure and room temperature abrasive wear resistance of chromium carbide reinforced NiM3Al matrix composite cladding at different depth on nickel base alloy were investigated. The results showed that there is a great difference in microstructure and wear resistance of the Ni3 Al matrix composite at different depth. Three kinds of tests, designed for different load and abrasive size, were used to understand the wear behaviour of this material. Under all three wear conditions, the abrasion resistance of the composite cladding at the depth of 6 mm, namely NC-M2, was much higher than that of the composite cladding at the depth of 2 mm, namely NC-M1. In addition, the wear-resistant advantage of NC-M2 was more obvious when the size of the abrasive was small. The relative wear resistance of NC-M2 increased from 1.63 times to 2.05 times when the size of the abrasive decreased from 180 μm to 50μm. The mierostructure of the composite cladding showed that the size of chromium carbide particles, which was mainly influenced by cooling rate of melting pool, was a function of distance from the interface between the coating and substrate varied gradually. The chromium carbide particles near the interface were finer than that far from inter-face, which was the main reason for the different wear resistance of the composite cladding at different depth.     

Abrasive performance of the chromium carbide reinforced Ni3Al matrix composite cladding in different depth

 The Microstructure and room-temperature abrasive wear resistance of chromium carbide reinforced Ni3Al matrix composite cladding in different depth on nickel base alloy were investigated. The results showed that there is a great difference in microstructure and wear resistance of the Ni3Al matrix composite in different depth. Three kinds of tests, designed for different load and abrasive’ size, were utilized to understand the wear behaviour of this material. Under all three wear conditions, the abrasion resistance of the composite cladding in the depth of 6mm, namely NC-M2, was much higher than that of the composite cladding in the depth of 2mm, namely NC-M1. In addition, the wear-resistant advantage of NC-M2 was more obvious when the size of the abrasive was small. The relative wear resistance of NC-M2 increased from 1.63 times to 2.05 times when the size of the abrasive decreased from 180μm to 50μm. The microstructure of the composite cladding showed that the size of chromium carbide particles, which was mainly influenced by cooling rate of melting pool, as a function of distance from the interface between the coating and substrate was gradual. The chromium carbide particles near the interface were finer than that away from interface, which was the main reason for the different wear resistance of the composite cladding in different depth.     

镍基合金─碳化铬复合涂层固体界面的结合问题

借助光学显微镜、扫描电镜、电子探针和Ｘ射线衍射仪等研究了４５钢表面镍基合金—碳化铬真空复合涂层固体界面的结合问题。结果表明，涂层在熔烧过程中，固体界面处不仅存在着由涂层向母材有较高的碳原子扩散，而且还有Ｆｅ，Ｎｉ，Ｃｒ原子的互扩散，从而形成致密牢固的冶金结合界面。     

微弧氧化对TC4钛合金微动磨损行为的影响

采用微弧氧化技术,在TC4钛合金表面制备高硬度氧化陶瓷层(MAO),对比研究了TC4钛合金基体与微弧氧化陶瓷层在2种不同位移幅值下的微动磨损行为.结果表明:位移幅值由80μm增大到150μm时,TC4钛合金基体微动损伤机制由粘着磨损和磨粒磨损转变为疲劳磨损和氧化磨损,而微弧氧化陶瓷层的损伤机制始终以氧化磨损为主;位移幅...     

镍基-碳化铬硬面复合涂层的疲劳强度

采用真空熔覆方法，在Q235－A试样表面制成厚0．1mm的镍基－碳化铬硬面复合涂层。通过试验比较涂层试样与无涂层试样的疲劳寿命。借助测量结合界面附近的化学成分，不仅得到了涂层与母材之间的元素扩散情况，而且能够分析界面的结合强度。     

Abrasive Wear Behavior and Mechanism of High Chromium Cast Iron

The abrasive wear behavior of high chromium cast iron(containing 12.9mass%chromium)austenitized at1 050 ℃for 2hand austempered in salt bath at 320℃for 4hwas evaluated.Abrasive wear was performed using alumina abrasive under four different loads,namely 50,100,150,and 200 N,for 36 000 cycles.The worn surfaces and wear debris were analyzed by scanning electron microscopy,laser confocal microscopy and X-ray diffraction.Microhardness profiles were also obtained in order to analyze the strain-hardening effects beneath the contact surfaces.Results indicate that the retained austenite in high chromium cast iron has experienced induced martensitic transformation after tests,for small amounts of retained austenite could be detected by X-ray diffraction.In addition,there is a close relationship between wear mechanism and test load.Under the condition of lower test load,the wear mechanism is an uninterrupted and repeated process,during which matrix is cut at first and then fine carbides flake off.As to higher test load,scratching and spalling induced by cleavage fracture of blocky carbide are the wear mechanism.     

Development of New Wear-Resistant Surface Coating at Elevated Temperature

Metal matrix composites containing a high vol-ume fraction of carbide particles are frequently usedas wear-resistant materials[1 -4]. For elevated tem-perature service in air ,the oxidation resistance andthe hot hardness of hard particle are the most i mpor-tant factors .In metal carbides ,tungsten carbide andchromiumcarbide can act as hard particles in metalmatrix in order to increase their hot hardness andthe ability of wetting metal matrix. Compared withtungsten carbide ,chromiumcarbide is …     

Corrosion Behavior of Electrodepositing Ni/Al2O3 Composite Coatings under the Presence of NaCl Deposit

The morphology and corrosion behavior of Ni/Al2O3 composite coatings prepared using double-pulsed electrodepositing technique after oxidized under 800℃ NaCl deposit in air environment were analyzed by scanning electrical microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrum (EDS). The results showed that the corrosion of all composite coatings was accelerated under NaCl deposits, and the corrosion products were rather porous with poor adherence to the matrix. Al2)O3 particles in the coatings can refine the grain size and improve the high temperature corrosion resistance of the coatings. Within the test scope, the more Al2O3 particles in the coatings, the lower corrosion rates could be obtained, and the corrosion mechanism was also discussed.     

Development of New WearResistant Surface Coating at Elevated Temperature

Because of good oxidation resistance at high temperature and excellent mechanical properties of Ni3Al and high hot hardness, and good oxidation resistance of chromium carbide, chromium carbide particle reinforced Ni3Al matrix composite would possess excellent wear resistance at elevated temperature. Cr3C2NiAlNi welding wire was produced by pressureless sintering process in vacuum. When the welding wire was welded on the surface of carbon steel, under the action of the physical heat of arc, NiAl reacted with nickel to form Ni3Al and carbide particle reinforced Ni3Al matrix composite was formed on the welding layers. Cr3C2 was dissolved during welding and dispersed Cr7C3 was formed, which strengthened the Ni3Al matrix significantly. The Cr7C3Ni3Al interface was broadened, and a zone of interdiffusion and a new phase M23C6 were formed, indicating that a good bond has been formed. The hardness of Cr7C3/Ni3Al composite at room and elevated temperatures is much higher than that of stellite alloys. In addition, Cr7C3/Ni3Al composite possesses better high temperature oxidation resistance than stellite 12 alloy. So Cr7C3/ Ni3Al composite can become an attractive potential candidate for elevated temperature wearresistant surface material.