挤压造粒机螺杆元件表面激光熔覆工艺研究

本文采用激光熔覆工艺在38ClMoAl基体上熔覆5～6 mm两种Cr18系列新型熔覆材料，分析熔覆金属的组织形貌，并测定其耐磨性和硬度变化；通过对比修复螺杆原件前后内孔花键尺寸，判定激光熔覆工艺修复过程中的变形量大小。研究结果表明，熔覆金属与基体结合良好，主要是以枝晶状马氏体为主，枝晶间弥散分布着硬质碳化物；在熔覆层与基体之间其形成细小的热影响区，熔池液体沿垂直于界面的最大散热方向快速生长，形成了明显的向上生长的胞状晶、树枝晶。1#熔覆金属硬度平均在50～52 HRC,2#熔覆金属的硬度平均在54～57 HRC之间；通过磨损对比可知，两种熔覆金属磨损失重分别是是45#淬火钢的68%和36%。检测对比螺杆元件修复前后的尺寸，采用激光修复后的零件尺寸变形量平均在0.12 mm以内，符合修复要求。     

激光熔覆法制备ZrO2-Y2O3涂层的显微组织与性能研究

采用预制粉末式激光熔覆法在钛合金(Ti-6Al-4V)表面制备了纳米ZrO2-8％ Y2O3涂层,利用X射线衍射仪(XRD)、扫描电镜(SEM)和光学显微镜(OM)对涂层的相组成及组织结构进行分析,同时分析了涂层的显微硬度分布情况.结果表明:在一定功率范围内,涂层气孔随激光功率增大而逐渐减少,裂纹随激光功率增大而增多;ZrO2陶瓷涂层与基体间结合良好,熔覆层微观组织结构主要以细小的树枝晶形态存在.在不同区域表现出不同的组织特征,靠近表面处晶体尺寸相对较小,呈柱状整齐排列在熔覆层表层区域;熔覆层中部主要包含块状晶及少量树枝晶;熔覆层底部主要为树枝晶,其一次品轴方向沿垂直于涂层截面方向生长;熔覆层主要由四方相(t相)ZrO2和立方相(c相)ZrO2组成;熔覆层平均硬度达到1000～ 1300 HV0.2,约为基材硬度的3.5倍.     

激光熔覆技术制备新型Al-TiC复合涂层的研究

采用预置激光熔覆技术,将Al-Ti-C混合粉末预置于铝合金基体表面,并在氩气保护下,利用YAG激光器实现了在铝合金表面原位形成Al-TiC复合熔覆层。通过改变激光束能量密度和激光束扫描速度等工艺参数,获得了不同工艺条件下的激光熔覆层,并对其显微组织、物相分布及耐磨性能进行比较研究。结果表明由于激光能量密度和激光束扫描速度不同,所形成的熔覆层中TiC的分布状态有很大差别。随着激光能量密度的增大,TiC分布趋于均匀。当激光束扫描速度为2.5mm/s、激光束能量密度为6.09 J/mm2时,熔覆层具有最高的耐磨性能。     

Ti6-Al4-V表面激光熔覆TiBCN粉末的研究

把TiBCN陶瓷粉末和Mn粉末混合(其中TiCB含量分别是100 wt%、95 wt%、90wt%、80 wt%和60 wt%)作为熔覆材料,用5 k W CO_2激光对Ti6-Al4-V(TC4)合金进行激光熔覆处理。用扫描电子显微镜(SEM)、能谱仪(EDS)和X-射线衍射仪(XRD)分析熔覆层中TiBCN颗粒的形貌和反应产物。观察发现,激光熔覆层没有形成裂纹,TiBCN颗粒发生部分熔化,并和金属发生反应生成TiN_(0.2)、Al_3Ti、TiAl和MnB等新相。TiBCN颗粒之间连接紧密,自动组装成枝晶状组织,与基体呈冶金结合状态。TiBCN颗粒和基体发生传质,基体中的Al元素扩散到TiBCN,形成多元Ti(Al)BCN固溶体。测试表明,熔覆层硬度明显提高达到HV1300,耐磨性比基体提高了4倍。     

Preparation of AI-TiC Composite Coating by Laser Cladding Technology

采用预置激光熔覆技术,将Al-Ti-C混合粉末预置于铝合金基体表面,并在氩气保护下,利用YAG激光器实现了在铝合金表面原位形成Al -TiC复合熔覆层.通过改变激光束能量密度和激光束扫描速度等工艺参数,获得了不同工艺条件下的激光熔覆层,并对其显微组织、物相分布及耐磨性能进行比较研究.结果表明由于激光能量密度和激光束扫描速度不同,所形成的熔覆层中TiC的分布状态有很大差别.随着激光能量密度的增大,TiC分布趋于均匀.当激光束扫描速度为2.5mm/s、激光束能量密度为6.09 J/mm2时,熔覆层具有最高的耐磨性能.     

汽车用AZ91镁合金的表面激光改性研究

为了解决压铸AZ91镁合金耐蚀和耐磨性能较差的问题,采用激光熔覆的方法在汽车用压铸AZ91镁合金表面制备了激光熔覆层,研究了激光功率和激光扫描速度对熔覆层成型、截面和表面形貌、物相组成、耐蚀和耐磨性能的影响。结果表明,过小/过大激光功率或者过大扫描速度会使得熔覆层中产生气孔、熔坑等缺陷;不同激光功率和扫描速度下,熔覆层与AZ91镁合金基体结合良好,AZ91镁合金表面激光熔覆层都主要由α-Mg、Mg₁₇Al₁₂、AlCu₄、Al₄MgY和MgAl相组成;随着激光功率增加,熔覆层表面晶界间距离和晶粒尺寸增大,熔覆层平均维氏硬度会逐渐减小;随着激光扫描速度增加,熔覆层厚度和熔覆层晶粒尺寸逐渐减小。激光熔覆层的耐蚀性和耐磨性都优于AZ91镁合金基体,Al-Cu/Y₂O₃熔覆层适宜的激光熔覆工艺为：激光功率1100 W、扫描速度500 mm/min,此时激光熔覆层与基体结合良好,熔覆层致密、晶粒细小、硬度较高,具有良好的耐蚀性和耐磨性。     

45钢表面激光熔覆WC／Co金属陶瓷

研究了45钢表面WC／Co金属陶瓷激光熔覆层的组织、界面特征及其形成机制,分析了激光熔覆层中涂层元素和硬度的分布特征。结果表明,激光熔覆使WC／Co等离子喷涂层的片层状组织特征消除,形成了连续致密的熔覆层;由于涂层中不同部位的成分。温度分布及冷速不同使初生相呈树枝状、多边形块状、花瓣状、条状及颗粒状等几种形态;实现了涂层与基体间的冶金结合,结合带宽度约3-5μp;涂层硬度达1794HV0.1。     

硬质合金覆层-钢基体结合界面层及其生长模型的研究

采用液相烧结技术制备的三元硼化物硬质合金覆层材料具有成本低廉、耐磨抗蚀的优异性能。利用覆层连结试样和抗弯强度法测定的覆层材料的覆层-钢基体界面结合强度为740MPa。覆层与钢基体之间的断裂破坏不是由于覆层与钢基体之间结合界面的剥离,而是发生于界面附近的钢基体和覆层内。利用显微硬度计测定了覆层-钢基体界面结合区的显微硬度变化,并利用SEM-EDS研究了覆层-钢基体界面微观结构和界面区元素分布。在覆层-钢基体结合界面处,存在由高硬度(覆层)到低硬度(钢基体)的狭窄过渡区,合金元素浓度分布没有突变,形成一个具有一定厚度的过渡层。分析了覆层-钢基体界面层形成的机理,并以扩散理论为基础,建立了覆层材料覆层-钢基体界面层生长的数学模型。     

TiC添加量对等离子熔覆Ni60–WC复合涂层性能的影响

在45钢上通过等离子熔覆制备了WC?TiC?Ni涂层,对其物相、显微硬度和滑动摩擦磨损行为进行了分析.结果表明:熔覆层与基体材料之间为冶金结合,熔覆层表面无裂纹和气孔.TiWC2的形成使得熔覆层的显微硬度和耐磨性得到提高.当TiC的添加量为20％(质量分数)时,涂层的平均显微硬度高达1072.5 HV,较WC/Ni熔覆层高了128 HV,此时涂层的耐磨性最好.     

粉煤灰活性氩弧熔覆Al2O3-TiB2-TiC复合涂层组织和性能分析

以铁基合金粉末、Al、TiO2和B4 C粉末为涂覆材料,以高铝粉煤灰、SiO2、MgO、CaF2和CeO2为活性剂,采用活性氩弧熔覆技术在Q235钢表面原位合成Al2O3-TiB2-TiC颗粒增强铁基复合涂层.测试熔覆涂层的物相结构、金相组织、显微硬度和耐磨性能,并与未涂覆活性剂的常规熔覆涂层进行对比分析.结果表明,复合涂层由Al2O3、TiB2、TiC、FeSi2 Ti、FeB2和α-Fe相组成,其与基体界面无气孔、裂纹等缺陷,呈良好的冶金结合;复合涂层测试点的最高显微硬度为1283.4 HV0.2,其在室温干滑动磨损条件下耐磨性良好;粉煤灰复合活性剂的加入可以促进熔覆层与母材之间的良好熔合、增加涂层中新相种类和数目、提高氩弧熔覆效率,这对改善复合涂层的综合性能具有重要意义.     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。