钢表面热喷涂层的超塑成形

本文介绍一种钢表面火焰喷涂自熔性合金超塑变形工艺，涂层合金在基材的超塑变形条件下与基材发生协调的超塑变形。通过超塑变形可使涂层内部孔洞基本消失，涂层与基材之间形成冶金结合，可实现金属构件超塑成形同时进行表面强化。     

工业态AZ31镁合金超塑压缩试验研究

利用Gleeble3800热模拟试验机，初步对工业态AZ31镁合金的压缩超塑性进行了研究。研究表明，工业态AZ31镁合金在变形温度为400℃，应变速率范围为1．6×10^-4～1×10^-2S^-1的条件下均表现出良好的压缩超塑性，其压缩真应变均超过1．83，应变速率敏感性指数达0．55。因此，对于不具有等轴晶粒的工业态AZ31镁舍金，无需经过细晶化预处理，同样可以得到良好的压缩超塑性，其研究结果具有很大实用价值。     

SiCp／Al复合材料高等静压下的性能研究

利用带小孔的恒定高压发生装置，通过高压拉伸、压缩及模锻试验，研究了ＳｉＣｐ／ＡｌＭＭＣ在高等静压下的性能及其随压力变化的规律。研究表明，ＳｉＣｐ／Ａｌ ＭＭＣ在室温高等静压下可进行大变形，得到质量优良的零件，认为高压变形是难变形ＭＭＣ成形的有效途径之一。     

在电场下的超塑变形

介绍在强电场下进行的超塑性拉伸实验，揭示了外加强电场及超塑变形条件对超塑性的影响。实验结果表明，电场降低了材料流动应力和应变硬化指数，提高了拉伸延伸率和应变速率敏感性指数，同时电场使空洞化速率减慢。还介绍了硬铝ＬＹ１２ＣＺ在强电场下超塑变形时的合理工艺参数。     

Si3N4颗粒增强铝基复合材料超塑性压缩试验研究

采用粉末冶金法制备出了体积分数为20Si3N4p/2124Al的铝基复合材料,初步研究了该材料的压缩超塑性,确定了该复合材料压缩超塑成形工艺参数,为这种复合材料超塑性成形的工程应用奠定了基础.研究表明,该复合材料在一定的工艺条件下可实现压缩超塑性,其最佳超塑压缩温度为515℃,最佳应变速率范围为1.225×10-4～1.225×10-3s-1.     

超塑性条件下的变形对高速钢组织和性能的影响

所谓超塑性就是指金属在一定条件下变形阻力小而能产生巨大塑性变形的能力。至少有三种超塑性:1)组织超塑性,这种超塑牲是具有稳定的细晶粒组织的金属和合金变形速度小时出现的;2)亚临界超塑牲,这种超塑性是接近相变开始时出现的(对钢来说一般稍低于A_(C1)点);3)马氏体超塑性,这种超塑性与马氏体转变同时出现(一般在M_(?)点至M_H点之间),此时将形成马氏体。研究表明,超塑性并不是某些特殊合金的性能,它对大多数变形合金来说,只要组织经过适当的准备,都可在一定条件下产生。所获得的研究结果包括高速钢、低合金钢和锰钢、钛合金、铝合金和镁合金进行的试验。本文仅介绍高速钢的试验结果。     

Fe加入NiAl金属间化合物中对塑性及热轧性能的影响

研究了Ｆｅ加入ＮｉＡｌ金属间化合物中对其塑性及热轧性能的影响。结果表明：ＮｉＡｌ合金中Ｆｅ含量增至１８．４ａｔ％，出现（β＋γ）双相组织，其室温塑性显著提高，压缩极限应变量可达３６．３％。首次发现具有（β＋γ）双相组织的１号合金在压缩变形过程中出现三阶段屈服现象。沿晶界分布的γ相的协调变形及β基体的动态再结晶使双相的１号合金获得良好的高温热轧性能，高温轧制总变形量可达８８．９％。     

超塑性锌铝合金注塑模

一、概述金属超塑性是指金属材料在一定温度一定变形速度条件下,延伸率大于100％,这种材料称为超塑性金属材料。超塑性ZnA122合金是国外首先研究的一类超塑性材料,在超塑金属中最先得到使用。目前超塑性ZnA122合金的研究和应用以苏联、日本比较活跃。     

有源强化传热控制薄板焊接压曲变形的研究

针对薄板构件焊接过程中压曲变形发生的力学机理,提出有源强化传热效应控制焊接压曲变形.应用数值方法研究了有源强化传热条件下的焊接温度场演变、分布及主要影响因素,为科学利用有源强化焊接传热效应提供了依据.研究表明,有源强化传热导致焊接温度场发生畸变,进而改变焊缝区压缩塑性应变量的大小与分布,从而达到有效地控制焊接应力与变形的目的.     

工具毛坯的超塑性挤压

具有一定组织的工具钢和高速钢,在AC_1减10～15℃到AC_1的温度范围内,以(1.33～2.13)×10~(-3)秒~(-1)的变形速度单向拉伸时,呈现超塑性挤压时,工具钢和高速钢出现超塑性的温度范围与单向拉伸时相同。但在高于10.0～12.0千巴的流体静压力下,出现超塑性的合适速度可增大几个数量级,同时组织因素的影响减弱。在(?)474型100吨滚压机上,在(10~(-2)～10~(-3))秒~(-1)的变形速度范围内和上述温度条件下,匀速挤压,实现了工具钢和高速钢模具毛坯及带柄刀具毛坯的超塑性挤压。超塑性挤压具有高的生产率,材料利用率达0.85～0.95。在超塑性挤压时,变形抗力大大降低。挤压产品的组织均匀。机械性能和使用寿命比切削加工产品提高1.8倍。     

Abrasive wear behavior of sprayed hydroxyapitite coatings by gas tunnel type plasma spraying

Hydroxyapatite (HA) coatings were sprayed using gas tunnel type plasma spraying at different arc currents. Abrasive wear test was carried out for the coatings sprayed at different arc currents under unlubricated conditions in air atmosphere. The abrasive wear rate was measured at different coatings thickness to study the effect of coating thickness on the anti-abrasion resistance of HA coatings. The results showed that the abrasive wear resistance of HA coatings increases as the operating arc current of the plasma torch increases. On the other hand, the abrasive wear rate reaches a minimum value near the substrate with coating thickness less than 50 μm. The results showed that the coating hardness increases in the region near the substrate and increases as the arc current increases. The experimental results indicated that there is a relation between the abrasion resistance and hardness properties of HA coatings.     

Effect of coating thickness on properties of Mo coatings deposited by plasma spraying

Plasma sprayed molybdenum coatings with different coating thicknesses (100, 200, 300 and 400 μm) were deposited on steel substrate. The variation in microstructural characteristics and properties of coatings with various thicknesses was investigated. The microhardness was measured using a Vickers’ indenter. The quantitative investigation of porosity is carried out with the help of computerised image analyser. The influence of coating thickness on wear resistance was estimated using pin on disc wear test rig. The worn surface of coated pin was characterised by scanning electron microscopy. The experimental results indicated that porosity of coating was increased with increased coating thickness. The enhanced coating thickness also resulted in decreasing microhardness and reduced wear resistance. In this study, the plasma sprayed thin coating with thickness of 100 μm possesses the lowest porosity, the highest hardness and better wear resistance.     

Influence of CrC addition in Ni-Cr-Si-B flame sprayed coatings on microstructure, microhardness and wear behaviour

In the present paper the influence of the addition of chromium carbide (CrC) particles on the microstructure, microhardness and abrasive wear behaviour of flame sprayed Ni-Cr-Si-B coatings deposited on low carbon steel substrate has been reported. Wear behaviour of the coatings was evaluated with a pin-on-block wear system against SiC abrasive medium (120 & 600 grades) over a range of normal load (5–20 N). It was observed that the wear behaviour is governed by the material related parameters (microstructure, microhardness of coating) and test parameters (abrasive grit size and normal load). The addition of CrC reduces the wear rate three to eightfold. Wear resistance was greater against coarse abrasives at high loads than against fine abrasives. Heat treatment of both unmodified (1004) and modified powder (1004-10%CrC, 1004-20%CrC) coatings deteriorated the abrasive wear resistance. SEM study of wear surfaces showed that wear of the coatings largely takes place by groove formation, plowing and scoring. Electron probe micro analysis (EPMA) of the coating was carried out for composition and phase analysis.     

MoS_2超细粉制备耐磨涂层及其性能分析

在不同的基体材料上采用MoS2 超细粉制备了耐磨涂层 ,并在SRV标准摩擦实验机上对涂层的耐磨性和减摩性进行了测试。结果发现MoS2 超细粉制备的涂层具有良好的减摩性能 ,摩擦系数为 0 0 4,而基体表面未作任何处理时喷涂的涂层耐磨性最好。     

TiN/Ti涂层在波箔轴承中的摩擦磨损性能

采用真空离子镀的方法在304不锈钢基体上喷涂厚度为3μm的TiN/Ti薄层,利用硬度计、三维形貌仪、划痕试验仪对涂层基本力学性能进行分析,通过球盘试验机分析涂层试样的摩擦磨损性能,根据波箔轴承性能测试实验台的测试结果:研究TiN/Ti涂层对基体表面耐磨减摩性能的影响。研究结果表明:TiN涂层硬度可达HV1 500,是基材硬度的5.5倍;TiN/Ti涂层平均摩擦因数为0.23,相对不锈钢304基材的平均摩擦因数0.71,降低了68%,磨损量也仅为基材的18.75%;GCr15与PTFE对磨的最大摩擦力矩可达2.4 N·mm,而TiN/Ti与PTFE对磨的最大摩擦力矩仅为1 N·mm,仅为GCr15的41.7%。TiN/Ti涂层表现出了优异的承载能力和耐磨减摩性能。     

高抗裂耐磨堆焊焊条的研制

为开发高抗裂高耐磨的堆焊焊条,采用H08A焊芯,通过调整药皮中的组分,设计了4种碱性焊条,然后分别在Q235钢基体上进行堆焊,采用光谱仪、硬度计、光学显微镜、扫描电镜和能谱仪等对堆焊层的化学成分、硬度和显微组织进行了分析,并研究了堆焊层的耐磨性和抗裂性。结果表明:优化成分焊条的堆焊层组织为混合型马氏体+少量残余奥氏体+弥散分布的一次NbC-TiC颗粒,低碳马氏体和高碳马氏体数量相当,硬度为58.1 HRC;堆焊层具有高的抗裂性能,连续堆焊不产生宏观裂纹;堆焊层的耐磨性也较好,约为淬火态45钢的1.41倍。     

采煤机滑靴激光熔覆铁镍基涂层的抗磨性能*

为提高采煤机滑靴在无油工况下的耐磨性,采用激光熔覆技术在45钢为基体上分别制备FeNiMo和FeNiMoSi涂层,并对其物相组成及硬度等进行分析。结果发现：制备的涂层结构致密,与基底保持了良好的冶金结合;FeNiMoSi涂层的平均硬度为438HV,分别约为基体（153HV）的2.8倍以及FeNiMo涂层（385HV）的1.1倍。通过往复式摩擦磨损试验机研究涂层的干摩擦磨损性能,并探讨其磨损机制。结果表明：随着载荷和滑动速度的增大,涂层的摩擦因数均呈现出减小的趋势;随着载荷的增大,涂层的磨损率逐渐升高;随着滑动速度的增大,FeNiMo涂层的磨损率出现先下降后上升的趋势,而FeNiMoSi涂层的磨损率则逐渐下降;涂层的磨损机制主要为磨粒磨损、塑性变形以及轻微的氧化磨损。总体来说,FeNiMoSi涂层相比FeNiMo涂层表现出更好的耐磨性能,这是因为涂层中Si元素的添加,不仅起到细晶强化作用,而且促进了FeSi金属间化合物相的生成。     

火焰喷涂PA1010/n-SiO2复合涂层干摩擦磨损性能

利用火焰喷涂法制备PA1010/n-SiO2复合涂层,并采用均匀试验设计方法研究涂层在干摩擦条件下同GCr15 钢环配副时的摩擦学性能;利用SPSS 12.0统计软件对试验结果进行回归分析, 建立涂层摩擦系数和磨损质量损失同pv值 (摩擦载荷与摩擦速度的乘积)相关性的数学模型;利用示差扫描量热仪(Differential scanning calorimetry, DSC)和扫描电子显微镜(Scanning electron microscope, SEM)对复合涂层的热性能和磨损表面形貌进行分析。结果表明,n-SiO2的加入能明显提高涂层的结晶性能、耐磨性能。当n-SiO2含量为1.5%时,复合涂层摩擦磨损性能最佳,在试验条件下磨损质量损失降低近4倍,摩擦因数降低23％,跑合期缩短44％,复合涂层与GCr15钢环对磨时的磨损机理主要为疲劳磨损和轻微的粘附 磨损。     

Improvement of the Oxidation and Wear Resistance of Pure Ti by Laser-Cladding Ti<Subscript>3</Subscript>Al Coating at Elevated Temperature

Ti₃Al coating was in situ synthesized successfully on pure Ti substrate by laser-cladding technology using aluminum powder as the precursor. The composition and microstructure of the prepared coating were analyzed by transmission electron microscopy, scanning electron microscopy (SEM), and X-ray diffraction technique. Thermal gravimetric analysis was used to evaluate the high-temperature oxidation resistance of the Ti₃Al coating. The friction and wear behavior was tested through sliding against Si₃N₄ ball at elevated temperature of 20, 100, 300, and 500°C. The morphologies of the worn surfaces and wear debris were also analyzed by SEM and three-dimensional non-contact surface mapping. The results show that the Ti₃Al coating with high microhardness, high-temperature oxidation resistance, and high temperature wear resistance. The pure Ti substrate is dominated by severe adhesion wear, abrasive wear, fracture, and severe plastic deformation at lower temperature, and severe adhesion wear, abrasive wear, plastic deformation, oxidation, and nitriding wear at higher temperature, whereas the Ti₃Al coating experiences only moderate abrasive and adhesive wear when sliding against the Si₃N₄ ceramic ball counterpart. In addition, the wear debris of the laser-cladding Ti₃Al coating sliding and Si₃N₄ friction pairs are much smaller than that of pure Ti substrate and Si₃N₄ friction pairs at elevated temperature.     

Effect of heat treatment on wear behavior of HVOF thermally sprayed WC-Co coatings

A WC-17Co coating was deposited onto ST37 mild steel substrate using HVOF spray technique and then heat treated at different temperatures in a vacuum chamber. The coatings were then evaluated in the as sprayed and heat treated conditions. Inspections by SEM and phase analysis by XRD indicated that some brittle eta (η) phases were produced at high temperature heat treatments. Generation of these phases increased the coating's hardness and decreased fracture toughness of the coating. Tribological properties were studied under dry condition by using pin on disc machine and diamond metal matrix composite disc as counterface. Wear test results showed that as sprayed deposit had the best wear resistance and its wear mechanism was sharp cutting abrasion. The weight loss in heat treated samples increased by increasing heat treatment temperature and the wear mechanisms gradually changed from cutting to gouging abrasion.