TC4钛合金表面激光熔覆NiCrCoAlY-Cr3C2复合涂层的摩擦和高温抗氧化性能

为了提高TC4 钛合金表面摩擦磨损和高温抗氧化性能,以 NiCrCoAlY+20%(质量分数)Cr3 C2 混合粉末作为熔覆粉末,采用激光熔覆技术在TC4 钛合金表面制备NiCrCoAlY-Cr3 C2 复合涂层,利用OM,SEM,XRD,EDS等分析涂层的显微组织和物相组成;采用 HXD-1 000TB 显微硬度计测量涂层显微硬度;采用 MMG-500 三体磨损试验机与 WS-G1 50 智能马弗炉对涂层和基体进行摩擦磨损及高温抗氧化实验.结果表明:利用激光熔覆技术在 TC4 钛合金表面可以制备形貌良好、无裂纹和气孔等缺陷的复合涂层.熔覆区显微组织结构致密,多为针状晶和树枝晶;结合区的显微组织主要由平面晶、胞状晶和树枝晶组成,生成了多种可提高耐磨性和高温抗氧化性的碳化物、氧化物和金属间化合物.复合涂层的最高显微硬度为 1344HV,约为钛合金基体 350HV的 3.8 倍;复合涂层的摩擦因数为0.2～0.3,较钛合金基体的摩擦因数0.6～0.7 明显下降;相同条件下复合涂层的磨损失重为0.00060 g,是钛合金基体磨损失重 0.06508 g 的0.9%;恒温 850 ℃氧化 100 h后复合涂层氧化增重为 6.01 mg·cm－2 ,约为钛合金基体氧化增重 25.10 mg·cm－2的24%.激光熔覆技术有效改善了TC4 钛合金表面的摩擦磨损和高温抗氧化性能.     

冷喷涂制备锡青铜/准晶复合涂层的微观结构及其摩擦学行为

利用冷喷涂技术制备锡青铜以及锡青铜/准晶复合涂层,采用光学显微镜、扫描电子显微镜以及硬度计等分析涂层的微观组织与微观硬度,对所制备的涂层进行干摩擦实验,并依据磨痕形貌分析主要磨损机理。研究准晶颗粒作为强化相粒子对于涂层的微观结构及摩擦行为的影响。结果表明:冷喷涂混合粉末所制备复合涂层表现出较高的致密度与微观硬度,硬质准晶颗粒表现出相对较低的沉积效率,复合涂层相对于纯青铜涂层具有稍低的摩擦因数与较高的磨损率,颗粒磨损对复合涂层的摩擦行为起主要作用。     

阴极弧离子镀制备AlCrN涂层的高温摩擦磨损行为

采用阴极离子镀在TiC金属陶瓷刀具表面制备了AlCrN涂层,采用球/平面接触方式考察了900℃高温时不同载荷作下涂层的摩擦磨损行为。通过扫描电镜观察了磨痕轮廓和微观形貌,并用能量散射谱和X射线衍射分析了磨损后涂层表面化学元素和物相的变化,讨论了载荷对涂层摩擦因数和磨损性的影响。结果表明,经900℃高温氧化后,涂层中N元素全部释放,形成Al和Cr的氧化物,改善了润滑性能和磨损性能;在载荷600,800和1000 g作用下,涂层摩擦因数平均值分别为0.1455,0.3939,0.4188,在载荷600 g时表现出优良的摩擦特性,适用于精密切削加工;在高温下AlCrN涂层表现为氧化磨损,同时伴随着少量的磨粒磨损和黏着磨损。     

搅拌摩擦加工铝基复合材料的高温摩擦磨损性能

通过在铝合金表面一定深度添加颗粒度为10μm的B4C粉末,采用搅拌摩擦加工方法制备成铝基复合材料.采用SEM、EDS、高温摩擦磨损试验机对其摩擦磨损性能进行研究;分析加工方法和环境温度对摩擦因数和磨痕形貌的影响,并探讨磨损机制.结果表明:高温磨损条件下,搅拌摩擦加工制备的铝基复合材料能明显改善铸态ZL109铝合金的耐磨性;复合材料表现出较好的磨损性能和较低的摩擦磨损因数.搅拌摩擦加工制备的铝基复合材料在100℃时磨损以氧化磨损和磨粒磨损为主,随着温度的升高,300℃时复合材料的磨损机理由氧化磨损转变为黏着磨损.     

等离子喷涂NiCrMo-NiCrBSi合金减摩涂层的摩擦磨损性能

内燃机在工作时活塞环与缸套发生摩擦,将造成能量损失与缸体的磨损损伤。针对缸套与活塞环的摩擦磨损问题,采用复合材料理论设计了成分为NiCrMo-30%NiCrBSi的复合减摩涂层。利用大气等离子喷涂技术,采用NiCrMo-NiCrBSi混合粉末制备了减摩涂层,研究了该涂层的断面组织、硬度及其在模拟缸套-活塞环摩擦磨损条件下的摩擦磨损行为。试验结果表明,采用混合粉末喷涂,可以获得结合良好、硬度适中(564 HV_{3 N})的复合涂层。在干摩擦磨损条件下,NiCrMo-NiCrBSi复合涂层表现出优异的综合耐磨损性能,涂层自身与对磨件(销)的磨损量都较小,且表面可生成MoO₂,降低摩擦系数;在油润滑磨损条件下,由于表面生成MoS₂,摩擦系数显著降低(稳定后约为0.1),复合涂层与摩擦副的磨损几乎可以忽略。     

多层石墨烯对钛合金摩擦学性能的影响EI北大核心CSCD

采用液相剥离法制备多层石墨烯(MLG)及MLG/Fe_(2)O_(3)复合纳米材料,将MLG,MLG/Fe_(2)O_(3)及MLG+Fe_(2)O_(3)直接添加至钛合金与钢的滑动界面上,通过干滑动摩擦磨损实验测试TC11合金的摩擦磨损行为。采用X射线衍射仪、激光拉曼光谱仪、扫描电子显微镜、3D激光扫描显微镜及能谱仪对磨损表面及亚表面的结构、形貌、成分进行分析。结果表明:只添加MLG时,TC11合金磨损失重及摩擦因数的变化趋势与未添加时类似,但磨损更严重。磨面上只含金属Ti,呈现出黏着痕迹、塑性撕裂、犁沟等黏着、磨粒磨损特征,基体发生塑性变形。添加MLG/Fe_(2)O_(3)复合和MLG+Fe_(2)O_(3)机械混合纳米材料时,磨损失重及摩擦因数在一定滑动转数范围内始终保持极低值,处于0附近。磨面上留有MLG和Fe_(2)O_(3)等物相,摩擦层为双层结构,呈现出典型的黑色、灰色区域。转数增至25000转时,添加复合材料时形成的双层摩擦层消失,转变为严重磨损,而添加混合材料时形成的双层摩擦层仍稳定存在。单独的MLG不能改善钛合金的摩擦磨损性能,在含Fe_(2)O_(3)摩擦层基础上添加MLG,形成的双层摩擦层兼具润滑和承载功能,可显著提高钛合金的减摩性和抗磨性。机械混合添加剂诱导形成的双层摩擦层中,因MLG层多且相对含量较高,钛合金表现出更为优异的摩擦学性能。     

原位自生WC增强Fe基涂层的组织及干滑动摩擦磨损性能

以Fe-Ni-W-C粉末为原料,采用等离子束原位冶金工艺在Q235表面经原位反应制备碳化钨(WC)增强Fe基涂层。利用扫描电镜、电子能谱、X射线衍射仪分析涂层的组织结构及原位自生WC的生长特征,考察涂层的干滑动摩擦磨损性能。结果表明:涂层中原位自生的WC生长为正三棱柱结构,其长大过程为沿〈0001〉方向在(0001)晶面层状堆叠生长,柱体最大长度接近60μm,属粗晶WC;相同干滑动摩擦条件下,与没有合成WC的Fe基涂层相比,原位合成有WC涂层的耐磨性显著提高(11倍),但由于WC柱体逐渐凸出涂层表面,造成摩擦因数波动增大,使摩擦过程稳定性逐渐降低;WC涂层的磨损机理主要为磨粒磨损和氧化磨损。     

304不锈钢激光原位合成自润滑涂层的宽温域摩擦学性能

由于304不锈钢在中、高温下摩擦学性能较差,制约了其在重要摩擦运动副零部件上的应用。为改善304不锈钢的摩擦学性能,以Ni60粉末为增韧相,WS2为合成润滑相的前驱化合物,TiC为高硬度耐磨相,采用高能激光束在其表面原位合成自润滑耐磨复合涂层。利用X射线衍射仪、扫描电子显微镜、显微硬度计、摩擦磨损试验机和探针式材料表面磨痕测量仪表征涂层和基体的物相、微观结构、显微硬度与表面形貌,并系统研究涂层和基体在20,300,600,800℃下的摩擦学性能及其磨损机理。结果表明:涂层主要由Cr0.19Fe0.7Ni0.11,Ti2SC,Fe2C,Cr7C3,CrS和WS2组成;涂层的平均显微硬度(302.0HV0.5)略高于基体(257.2HV0.5),但涂层上部区域的硬度(425.4HV0.5)约为基体的1.65倍;涂层在所有等温摩擦学实验中摩擦因数和磨损率均低于基体,300℃时涂层润滑效果最好,摩擦因数为0.3031,600℃时涂层耐磨效果最好,磨损率为9.699×10^-5 mm^3·N^-1·m^-1。     

不同硬度铝硅聚苯酯涂层的刮磨机理

目前,国内外关于铝硅聚苯酯涂层刮磨试验研究报道较少。采用等离子喷涂技术(APS)制备了3种不同硬度的铝硅聚苯酯涂层,并利用自制的刮磨试验机进行刮磨试验。采用激光共聚焦显微镜(CLSM)、扫描电镜(SEM)及能谱仪(EDS)等研究了硬度对铝硅聚苯酯涂层刮磨机理及可磨耗性能的影响。结果表明:3种涂层在刮磨前期均发生的是叶尖微峰与涂层之间的二体磨粒磨损,后期主要为三体磨粒磨损和黏着磨损;低硬度涂层以非金属相的黏着磨损为主,造成了较大的刮磨深度和面粗糙度;高硬度涂层发生了严重的三体磨粒磨损和黏着磨损,造成了最大的刮磨深度和面粗糙度;中间硬度涂层发生了适中程度的三体磨粒磨损和黏着磨损,得到了较小的刮磨深度和面粗糙度,具有最佳的可磨耗性能。     

WC／C固体润滑涂层的滑动摩擦磨损性能研究

在CETR UMT-2摩擦磨损试验机上用Si3N4陶瓷球和纯钛(TA2)球作为对磨副,对物理气相沉积(PVD)方法制备的WC/C固体润滑涂层进行了球一盘式的滑动摩擦磨损实验.利用光学显微镜(OM)、扫描电子显微镜(SEM)和电子能谱(EDX)对磨损表面进行了微观分析,探讨了WC/C涂层的摩擦磨损机理.结果表明:滑动速度对WC/C涂层的摩擦特性影响很大,较小的滑动速度有利于在两种对磨副的磨痕表面形成致密连续的转移膜.Si<,3>N<,4>球作为对磨副时,WC/C涂层的损伤主要表现为剥层及氧化磨损;纯钛球作为对磨副时,涂层损伤表现为轻微的磨粒磨损和氧化磨损,WC/C涂层拥有良好的抗钛粘着性能.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.