激光熔覆Al65Cu2OCr15准晶态合金的相选择问题

研究了在45#钢基体表面激光熔覆Al65Cu20Cr15准晶态合金过程中，工艺参数激光功率（P）和扫描速度（v)对激光熔覆涂层相结构的影响。结果表明，激光功率和扫描速度的变化使基体材料对熔覆涂层的稀释率发生改变，随着激光熔覆稀释率的增加，熔覆层的相结构依次为λ＋I，I＋β，β，β＋d，d Fe，激光熔覆涂层相结构的差异使涂层具有不同的显微硬度，参数δ（P／v)决定激光熔覆过程的稀释度，从而直接影响激光熔覆准晶涂层的相结构，涂层的表面显微硬度也因涂层相结构的不同而有所差异。     

熔覆电流对Inconel 625涂层组织与性能的影响

为了提高合金钢表面熔覆镍基合金涂层的质量,研究工艺参数对镍基合金涂层性能的影响,采用等离子熔覆技术制备Inconel 625涂层,利用金相显微镜、XRD观察并测试涂层的显微组织形貌与物相组成,采用电化学方法、显微硬度测试以及摩擦磨损试验研究了熔覆电流对涂层耐蚀性能和耐磨性能的影响规律。结果表明：熔覆电流改变了Inconel 625涂层的组织形貌和γ-Ni相不同晶面的择优倾向,当熔覆电流为80 A时获得组织细小、结构致密、(111)晶面择优生长的镍基合金涂层;与熔覆电流分别为60,70,90 A条件下制备的涂层相比,该涂层的腐蚀倾向最小,腐蚀速率最低,钝化区间最大,耐蚀性能优异;Inconel 625涂层的显微硬度值显著大于基体,当熔覆电流为80 A时涂层的显微硬度值最大,约为基体的1.89倍,耐磨性能最佳。     

激光熔覆制备Al65 Cu20 Cr15准晶态合金及其类似相的研究

研究了以45＃钢基体表面激光熔覆准晶态Al65Cu20Cr15粉末制备准晶及其类似相涂层过程中，激光功率和扫描速度对激光熔覆涂层相结构的影响。实验结果表明：由于激光切率和扫描速度的变化，基体材料对熔覆涂层的稀释程度发生改变；随着激光熔覆稀释率的增加，熔覆层的相结构依次为β＋i,β d,β,β Fe；激光熔覆粉末所制备的涂层结构致密，无孔隙和裂纹；涂层的表面显微硬度及摩擦系数等力学性能也因涂层相结构的不同而有所差异。     

SiC含量对激光熔覆SiC/Ni60A复合涂层显微组织和耐磨性能的影响

利用LDM2500-60半导体激光器在45#钢板上制备SiC颗粒增强Ni60A合金激光熔覆涂层,系统研究SiC含量对涂层的显微组织、稀释率、耐磨性、摩擦因数和显微硬度的作用规律。结果表明:随着SiC含量增加,熔覆表层的微观组织细化,稀释率、耐磨性、摩擦因数和硬度均先增加后降低;当SiC含量为20%(质量分数,下同)时,熔覆层的耐磨性能最佳,磨损量仅为0.0012g,为基体磨损量的1/36.3;摩擦因数最小为0.464,且磨损过程最为平稳;熔覆层平均硬度值最高,达到1039.9HV0.2,为基体的3.5倍;但当SiC含量达到25%时,熔覆层的显微硬度与耐磨性能反而下降。     

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.     

激光熔覆镍包石墨和石墨烯复合涂层组织和性能分析

采用激光熔覆技术在40CrNi2Si2MoV钢基体表面分别制备镍包石墨和石墨烯复合涂层,测试分析了涂层的物相、微观组织、显微硬度以及摩擦磨损性能。结果表明:激光熔覆涂层主要由γ-Ni、Ni_3B、M_(23)C_6和M_7C_3相组成,均为树枝晶和共晶组织;从熔覆层表面到基体的显微硬度呈现出四个台阶,硬度最高值出现在亚表层;两种涂层均具有较好的减摩性能和耐磨性能。     

Ni60A+20WC于水刀喷嘴耐磨层的应用工艺

采用高频感应熔覆技术以提高高压水刀喷嘴的耐磨性能,本实验选用304不锈钢板作为基体材料,Ni60A+20%WC合金粉末作为熔覆层材料;分别采用高频感应加热设备、电火花成型机和小孔机对试件进行加热、熔覆并加工到规定尺寸.采用扫描电子显微镜观察试件的微观组织,发现涂层和基体之间产生了扩散层;采用X射线衍射仪分析涂层相结构,涂层中存在的强化相有WC、Fe_3Ni_2、W2C、Cr_3C_2、Cr_2Ni_3等;摩擦学性能测试实验表明涂层材料大大提高了水刀喷嘴的耐磨性;显微硬度实验表明WC极大地提高了涂层的硬度,其平均值约为1 000 HV0.1,基体约为190 HV0.1.在水刀喷嘴内孔成功制备了WC增强Ni基熔覆层,该熔覆层光滑平整,表面无明显缺陷,与基体实现冶金结合,性能优异.     

合金成分对镍基合金激光熔覆涂层组织与性能的影响

为了研究激光熔覆镍基合金涂层显微组织与性能之间的关系,本文选用Ni25、Ni45、Ni60镍基自熔性合金粉末作为熔覆材料,在同一工艺参数下在45#钢基体上制得Ni25、Ni45、Ni60合金激光熔覆涂层。利用扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)、显微硬度计等方法对涂层的显微组织、物相组成、显微硬度等进行了研究。结果表明从Ni25到Ni60合金涂层,随着合金元素含量的提高,涂层微观组织逐渐由亚共晶转变为过共晶,γ-Ni奥氏体枝晶所占体积分数减少,尺寸细化,枝晶间的共晶组织和硬质相所占的体积分数增大,涂层和基体之间结合带的宽度越来越窄,熔覆层的显微硬度越来越高。Ni25、Ni45合金涂层的平均显微硬度分别为250HV和550HV左右,而Ni60合金涂层的平均硬度却高达750HV左右,为Ni25合金涂层的3倍。     

原位自生WC-Cr_3C_2复相陶瓷增强铁基表面复合材料

采用激光熔覆协同燃烧合成表面涂层技术在铁基材料表面原位生成复相陶瓷涂层。利用扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)等方法对涂层的物相组成、显微形貌、组织成分等进行了研究,结果表明涂层主要是由WC、Cr3C2、-σFeCr和Fe2W所组成的复相体系。界面形貌特征表明涂层与基体之间为冶金结合。硬度及摩擦磨损试验表明,涂层的硬度及耐磨性能明显高于基体材料。热震实验结果显示涂层与基体具有良好的结合力。     

Ti811合金表面激光熔覆Ti2Ni+TiC+Al2O3+CrxSy复合涂层的组织和性能

以TC4+Ni45+Al₂O₃+MoS₂+Y₂O₃混合粉末为熔覆材料,采用同轴送粉技术在Ti811合金表面进行激光熔覆制备复合涂层,使用SEM、EDS和XRD等手段分析了涂层的微观组织,测试了涂层的显微硬度和摩擦磨损性能。结果表明,在激光熔覆过程中Ti811合金中的Ni和C分别与Ti发生反应,原位生成金属间化合物Ti₂Ni和硬质增强相TiC;MoS₂分解后S与Cr发生硫化反应生成了软质润滑相Cr_xS_y。网状形态的Ti₂Ni、近球状和枝晶形态的TiC以及点状的Al₂O₃,均匀分布在熔覆层中。硬质相强化和软质相润滑的共同作用,使激光熔覆层具有较高的显微硬度和较优良的耐磨性能。激光功率为900 W的熔覆层其平均显微硬度值达1303.5HV_0.5,其耐磨性能最佳。     

Al20Si20Mn20Fe20Ga20中近等原子比高熵十次准晶

准晶是结构复杂相,通常以一种合金元素为主要成分.高熵合金含有多种主要合金元素,其晶体结构却往往是比较简单的立方相.作为结构和成分均复杂的高熵准晶却难以在实验上制备和理论上预测,研究人员对其结构特点也知之甚少.因而高熵准晶的制备和结构特性引起了人们的广泛关注.我们报道了一种在Al20Si20Mn20Fe20Ga20甩带样...     

Room‐Temperature Mechanical Properties of V20Nb20Mo20Ta20W20 High‐Entropy Alloy

Refractory high‐entropy alloys (HEAs) have shown promising high temperature strengths, while their mechanical behaviors at room temperature are rarely reported. In this work, the room‐temperature mechanical properties of V₂₀Nb₂₀Mo₂₀Ta₂₀W₂₀ refractory HEA under various different loading modes including tension, compression, bending, shear loading, and microhardness are investigated. The results show that this alloy exhibits very high compressive strength but quite low strengths under tension, bending, and shear loading, similar to the conventional brittle materials. However, pronounced plasticity and slip bands are observed in compression samples, and no indentation cracking is observed in low‐load microhardness tests, which indicate the potential ability of plastic deformation in this refractory HEA. The present work suggests that the microstructure or composition of this HEA should be carefully tailored before its practical usage to suppress its large tendency for cracking and eventually improve its ductility and strength under tension.

     

Synthesis of MnAPO-20, CoAPO-20, NiAPO-20, and CuAPO-20 using tetrahedral tetrahalometallates

Highly crystalline MnAPO-20 and CoAPO-20 have been prepared at previously unreported substitution levels using tetrahedral tetrahalometallates. X-ray diffraction and infrared spectroscopy indicate that framework substitution of manganese and cobalt has taken place. Samples have also been studied using X-ray fluorescence, scanning electron microscopy, thermogravimetric analysis, and a Gouy balance. MnAPO-20 and CoAPO-20 synthesized with metal(II) acetates using the same molar ratios were not as pure as those synthesized using the tetrahedral complexes even at low substitution levels. Interplanar spacings and unit cell sizes were found to be smaller in these traditionally prepared AlPO₄-20 analogs, indicating less framework incorporation of the transition metal. NiAPO-20 and CuAPO-20 have also been prepared by this method, although framework substitution of Ni(II) and Cu(II) is not confirmed.     

Pseudo-quinary Ti20Zr20Hf20Be20(Cu20 -xNix) high entropy bulk metallic glasses with large glass forming ability

A series of pseudo-quinary Ti₂₀Zr₂₀Hf₂₀Be₂₀(Cu_20 -xNi_x) (x = 2.5, 5, 7.5, 10, 12.5, 15, 17.5 and 20 at.%) high entropy bulk metallic glasses (HE-BMGs) with large glass forming ability (GFA) were successfully prepared by copper mold tilt-casing. The critical diameters (D_c) of these HE-BMGs are all above 12 mm. In particular, the developed Ti₂₀Zr₂₀Hf₂₀Be₂₀(Cu_7.5Ni_12.5) and Ti₂₀Zr₂₀Hf₂₀Be₂₀Ni₂₀ high entropy alloys (HEAs) can be produced in the amorphous state with diameters up to 30 mm and 15 mm, respectively, which are the largest HE-BMG and quinary HE-BMG hitherto. The two HE-BMGs also exhibit high yield strength, together with the plastic strain values of (3.0 ± 1.1) % and (4.0 ± 0.9) %, respectively. With increasing Ni additions in the pseudo-quinary HEAs, the crystallization growth resistance and thermal stability have been improved, which is apparently due to the sluggish diffusion of the atoms in the HEAs.     

Track nanodosimetry of 20-MeV protons at 20 nm

Track nanodosimetry is the theoretical and experimental research which studies the stochastic aspects of ionisation yield produced by ionising particles in nanometric target volumes, positioned at different distances from the primary particle track. The STARTRACK experimental set-up, mounted on the +50° beam line at the Tandem-Alpi particle accelerator of Legnaro National Laboratories, has been conceived to give an experimental basis to nanodosimetric calculations. STARTRACK is a detection system able to measure the ionisation cluster-size distributions in a 20 nm propane site, by counting the electrons set in motion by different ion tracks, with the resolution of one electron. The 'sensitive volume' SV can be moved at different distances from the primary particle track (different impact parameter). Distributions of 20-MeV protons have been measured and compared with Monte Carlo calculations.     

ZKP—20型二十工位真空开关管排气台

介绍了ＺＫＰ－２０型二十工位真空开关管排气台的结构设计，采用ＰＣ工业程序控制系统，实现了整个排气工艺过程的自动化，降低了操作人员劳动强度，提高了生产效率。