不同温度下TC21钛合金表面Cr-Al共渗层的耐磨性分析

为了提高TC21钛合金的耐磨性,采用双辉等离子渗金属技术对其进行了Cr-Al共渗。采用扫描电镜、能谱分析和X射线衍射分析了Cr-Al共渗层的微观组织形貌、物相组成等。采用硬度测试仪、纳米压入仪测定了Cr-Al共渗层的硬度和弹性模量。在20℃、300℃和500℃对基体及共渗层进行了球盘磨损试验,分析其磨损机制。结果表明,Cr-Al共渗层均匀致密,厚度为35μm,表面硬度达到950 HV0.1,约为基体的2.9倍;纳米硬度为7 506 MPa,弹性模量为506 GPa,分别是基体的2.4倍和3.3倍;TC21合金经Cr-Al共渗后,在以上三种温度下耐磨性均得到了提高。在20℃,TC21合金基体主要发生磨粒磨损、黏着磨损和氧化磨损,Cr-Al共渗层发生磨粒磨损和轻微的氧化磨损;在500℃,TC21合金基体的黏着磨损、氧化磨损及剥层磨损加剧,Cr-Al共渗层则处于氧化磨损与剥层磨损的动态平衡中。     

机械能助Al-Zn-Cr共渗工艺及渗层组织

采用机械能助渗技术,在600℃温度下对20钢进行Al-Zn-Cr共渗试验。利用光学显微镜、扫描电镜(SEM)、能谱仪(EDS)等仪器,分析合金元素铬对渗层组织共渗速率的影响,分析助渗时间对渗层组织的影响,测定铬在渗层中的分布,以及铬含量对渗层厚度的影响。结果表明:在机械能助Al-Zn-Cr共渗的研究中,铬含量的增加促进了渗层厚度的增加,而铬在渗层中分布相对均匀,无富集现象。在相同助渗时间下,铬含量的增加,促进了共渗速率的提高,促使渗层组织由单一的铁铝渗层组织转变为铁铝、铁锌多层渗层组织。在同一渗剂配比条件下,助渗时间的延长,促进Fe-Zn相形成,Fe-Al相减少。在助渗条件为600℃、3 h、5%Cr时,渗层为α-Fe(富锌)、Fe_3Zn_(10)、FeZn_7、FeAl等相组成的多层组织,而且相对致密;渗层兼顾抗氧化性和阴极保护作用。     

硼-铬-稀土低温共渗剂的研究

应用优化设计实验原理,经方差分析,确定了稀士、氟硅酸钠和硅钙合金的最佳配比,获得了一种廉价的固体渗硼剂.利用此渗剂对45钢进行650℃×6 h的低温共渗处理.通过对渗层组织观察和渗层相结构及硬度的测定,研究了渗硼层的组织性能.结果表明:共渗层呈梳齿状,钢件表面获得单相共渗层Fe2B,且具有较高的硬度.     

包埋渗剂Al含量对N80套管钢渗层组织和性能的影响

选用不同Al含量配比的渗铝剂,对N80套管钢进行包埋渗铝处理,形成渗铝层。阐述了包埋渗铝过程,并依次表征了不同Al含量渗剂所得渗铝层的金相组织、元素分布、物相组成和显微硬度。结果表明:采用不同Al含量的渗剂在950℃真空条件下可以在N80钢基体表面获得450～650μm厚度连续的渗铝层组织;渗铝层厚度随渗剂中Al含量增加而增厚;渗层组织从表面向基体方向Al含量呈梯度减少;渗剂中Al含量的不同引起渗层的物相变化,10%和20%Al含量的渗剂所得渗层组织为Fe3Al相,35%Al含量的渗剂所得渗层组织为FeAl相;不同Al含量渗剂下所得渗铝试样渗层组织的显微硬度均高于基体,从渗层表面向基体方向延伸,显微硬度逐渐降低趋于平缓。     

氯化铵、海绵钛、稀土和固态铬酸盐复合催渗剂的作用与机制

研究了3Cr2W8V、T10和20CrMnTi钢采用氯化铵、海绵钛、稀土和固态铬酸盐复合催渗剂进行氮碳共渗后渗层的组织和成分。结果表明,这种复合催渗剂对上述钢种有明显的催渗作用。其机制为,提高工件表面的洁净度,活化工件表面,促进NH3和C2H5OH分解,吸附炉气氛中的有害物质及改善渗层的组织结构。     

钢的粉末硼铝共渗研究

本文主要对45钢进行粉末硼铝共渗,分析了共渗过程中的主要化学反应,研究了渗剂硼、铝含量对渗层厚度和组织结构的影响,测定了渗层的残余应力及各项基本性能。结果表明,通过调整渗剂成分,可以控制共渗层的组织结构,从而获得所需要的、优于渗硼层的性能。     

CeO2对Cr-Al渗层组织和高温氧化性能的影响

采用浆料包渗法,以Cr2O3,粉为渗Cr源,纯Al粉为还原剂,NH4Cl作为活化剂,Al2O3,为惰性添加剂,蛋白质(鸡蛋清)为粘结剂,在Cu表面预先镀Ni随后浆料包渗Cr、Al,制备Cr-Al共渗层.研究了稀土氧化物CeO2对Cr-Al渗层的组织和氧化性能影响.结果表明:渗剂中添加CeO2氧化物后,渗层组织由Cr、Al的固溶体为主转变为Ni3Al金属间化合物和固溶体两相混合;与不加稀土氧化物相比,改性后渗层氧化增重由纯铜的1/6降低到1/11,氧化产物为Cr2O3、Al2O3和少量的NiO,氧化层致密,没有明显的裂纹和空洞出现,改善r铜表面抗高温氧化性能.     

45钢渗硼工艺的正交分析研究

研究了渗硼温度、供硼剂种类、活化剂种类及其含量对渗硼层厚度和质量的影响，并对硼砂型渗硼剂中加入硅铁作为还原剂对渗硼效果的影响也进行了研究。结果表明：温度与供硼剂种类是45钢渗硼的主要影响因索；45钢渗硼的最优工艺方案为：供硼剂选用B4C 稀土，活化剂为Na3AlF6，活化剂含量为20％～30％，温度为950℃；以硼砂为供硼剂的渗硼剂中加入硅铁粉能提高渗硼层的厚度及渗硼质量。     

冷塑性变形对20钢硼-铬-稀土高低温共渗的影响

对经压缩和喷丸的20钢分别在850和680℃进行4h硼-铬-稀土共渗,分析了共渗层的组织、层深及其显微硬度。结果表明,低温共渗层的组织比高温共渗层的致密,疏松、孔洞少;冷塑性变形在两种工艺条件下都明显促进了渗硼的进行,且都随着变形量的增加渗层深度增加;高温共渗得到FeB和Fe2B双相硼化物,低温共渗得到单一Fe2B相;冷塑性变形对渗层的硬度基本没有影响。     

铝钛共渗及稀土的影响

用粉末法对20、45钢进行铝钛共渗,结果表明,采用双层密封比单层密封能获取更厚的渗层,此外,当以TiO_2为供钛剂时,AlF_3是适宜的活化剂,而以Ti粉为供钛剂时,NH_4F比AlF_3更好,在共渗剂中掺入稀土可使渗层厚度增加30%以上,稀土的催渗效果与扩渗温度和稀土掺入量等有关。     

水蒸气对NiCrAlY涂层抗高温氧化性能的影响

采用热重分析及现代表面分析方法研究了低压等离子喷涂Ni CrAlY涂层在纯氧以及含5%水蒸气的O2中的高温氧化行为,结果表明：在纯氧的氧化环境中 ,NiCrAlY涂层氧化动力学遵循抛物线规律,在含有5％的水蒸气的O2中,NiCrAlY涂层在氧 化至110 h后氧化动力学几乎呈直线规律.XRD及SEM分析显示,NiCrAlY涂层在O2中氧化180 h后,表面形成一层致密的Al2O3;而在含5%水蒸气的O2中氧化180 h后表面氧化层中 除了有Al2O3外,还有NiO和Cr2O3.其原因在于水蒸气中的氢在氧化物中的溶解,致 使Ni2+扩散 速度增加,使氧化层变得疏松,降低其抗氧化性.     

Cr-Al(Cr)2O3金属陶瓷的燃烧合成与致密化

采用燃烧合成法，通过调整反应体系成分并控制凝固过程，成功制备了金属Cr相分布均匀、尺寸可达亚微米级的Cr-Al(Cr)2O3金属陶瓷．研究了聚合物及体系成分对金属陶瓷微观组织和燃烧合成过程的影响．结果表明，添加聚合物显著降低了Al-Cr2O3-A12O3体系的引燃温度，缩短了引燃时间，并改善了Cr颗粒在陶瓷基体上的分布均匀性．加入稀释剂Al2O3以及Cr2O3过量可细化Cr颗粒，使Al2O3基体变为Al2O3和Al(Cr)2O3．对燃烧合成熔体施加较低的压力，获得了致密的Cr-Al(Cr)2O3金属陶瓷，解决了燃烧合成致密化的问题．     

钼合金Si-Cr-Ti-SiC-MnO2涂层的制备与组织性能

目的提高钼合金表面红外辐射性能与高温抗氧化性能。方法将40%Si、20%Cr、5%Ti、5%SiC、30%Mn O_2五种粉末与酒精、粘结剂按比例混合,经高能球磨6 h后制得均匀悬浮的料浆。采用浸涂工艺对预处理的钼合金试样进行料浆涂覆,在1450℃真空烧结0.5 h后制得黑色涂层试样。通过1550℃高温静态氧化试验和高温粒子薄片红外光谱综合实验系统,分别评价涂层抗氧化性能和红外辐射性能,并通过扫描电镜(SEM)、能谱分析(EDS)、X射线衍射仪(XRD)对涂层氧化前后的形貌与组织结构进行分析。结果钼合金Si-Cr-Ti-SiC-Mn O_2涂层在700、900℃的法向发射率分别达0.85、0.88,在1550℃高温有氧环境下的静态抗氧化寿命达7 h。原始涂层呈四层复合梯度结构,由外到内分别为SiO_2+Mn3O_4+M5Si3(M指Mo、Cr、Ti)、M5Si3+Mo Si2+SiC+Mn3O_4、Mo Si2、Mo5Si3。高温氧化后,涂层四层复合结构由外到内转变为SiO_2+(Cr,Ti)5Si3+Mn Cr2O_4+Mn3O_4、M5Si3+SiC+Mn Cr2O_4+Mn3O_4、Mo Si2、M5Si3。高温氧化过程中,MSi2高硅化物层逐渐转变为M5Si3低硅化物层,涂层表面形成含Mn Cr2O_4尖晶石相和复合硅化物的致密SiO_2玻璃膜。结论 Si-Cr-Ti-SiC-Mn O_2涂层可有效提高钼合金基体的红外辐射性能和高温抗氧化性能,复合硅化物与硅锰复杂氧化物具有良好的抗氧化性能、高辐射性能和自愈合性能。     

Corrosion-erosion resistance of Zn-Al co-cementation coatings on carbon steels in aqueous media

A novel Zn-Al co-cementation coating was obtained by a pack cementation method,This coating possesses a two-layered structure,The outer layer is mainly composed of Fe2Al3 and FeAl intermetallics with a small amount of Zn,and the inner layer consists of Zn,Fe and a small amount of Al.The corrosion-erosion resistance of Zn-Al con-cementation coatings on carbon steel was studied by a rotary corrosion method in various NaCl and H2S containing solutions and relevant SiO2 containing media,The experimental results are compared with those of carbon steels and the sherardizing and aluminizing coating ,showing that the Zn-Al co-cementation coating have excellent corrosion-erosion resistance in various aqueous media.     

High Temperature Oxidation and Wear Resistance of Y-modified Hot Dipping Aluminized Coating on SCH12 Steel

Microstructures,high-temperature oxidation and wear resistance of hot dipping Al-Si-Y coating on SCH12 heat resistant cast steel were investigated in this study.The aluminized coating was characterized by scanning electron microscopy(SEM),energy dispersive X-ray spectrometry(EDX)and X-ray diffraction(XRD).The results showed that the coating was composed of the Al-rich outer layer and the intermetallics inner layer.In the Al-rich layer,some Y-rich precipitates and Fe-Al-Si-Cr precipitates could be observed.The intermetallics layer presented three layers induced by the increase of Fe,Cr,Ni content and the corresponding decrease of Al,Si content.The oxidation tests were conducted in still air at 850℃for up to 100 h.After oxidation,a top oxide scale composed of mainlyα-Al2O3,Al5Y3O12 was formed on the steel surface.The intermetallics beneath the oxide scale consisted of mainly FeAl and small amount of Fe2Al5 and Cr3Si phase.The mass gain of the coated and uncoated SCH1steel is 0.45 mg/cm 2 and 0.57 mg/cm 2,respectively.The wear resistance was investigated using a high-temperature pin-on-disc tribometer at 650℃.The wear rate for the coated and uncoated steel is 0.45μm 3 /μm.N and 3.01μm 3 /μm.N,respectively.The high temperature wear tests and oxidation tests results demonstrated that the yttrium-modified aluminized specimen had significantly improved high-temperature wear resistance and equivalent oxidation resistance compared with the original SCH12 specimen.     

DD6单晶高温合金的等温氧化行为(英文)

研究第二代单晶高温合金DD6在1050℃和1100℃下的等温氧化行为,分别采用SEM、XRD和EDS对氧化产物进行分析。结果表明,在1050℃和1100℃温度下,DD6合金的100h氧化动力学曲线遵循亚抛物线规律。在1050℃时,氧化产物分为两层,外层为NiO和少量的Al2O3,内层为Al2O3。而在1100℃时,氧化产物分为三层,外层为Al2O3和少量的NiO,中间层为Cr2O3和TaO2,内层由Al2O3组成。在这2种温度下的氧化物下面都形成了无γ′相的区域。     

Oxidation Behavior of K4750 Alloy at Temperatures Between 750 ℃and 1000 ℃

This study investigated the oxidation behavior of a new casting Ni-based superalloy K4750 at 750 ℃-1000 ℃ in air for 100 h-1000 h by isothermal oxidation tests.The oxidation-kinetic curves were plotted by the static discontinuous weight gain method.Observation and identification of oxidation products were conducted using scanning electron microscopy(SEM),energy dispersive spectroscopy (EDS),electron probe micro-analysis (EPMA) and X-ray diffraction (XRD).X-ray photoelectron spectrometer (XPS) was also used to analyze the chemical state of elements and the distribution in depth.The results showed that the oxidation-kinetic curves of K4750 alloy basically obeyed the parabolic law.The average oxidation rate below 900 ℃ was less than 0.1 g/m2.h which meant the alloy was at a complete anti-oxidation grade,and the alloy was at an anti-oxidation grade at 1000 ℃.The predominant surface oxide was Cr2O3,and a double layer structure of the oxide scale was observed at all tested temperatures as time increased.The outer oxide layer contained continuous Cr2O3 and a small amount of oxides mixed TiO2 and NiCr2O4,while the inner oxide layer was composed with Al2O3.The oxidation process could be interpreted by the competitive oxidation of different elements.The diffusion rate of Ti through Cr2O3 layer increased with increasing temperature,and thus the generation of TiO2 was advantageous.The dispersed TiO2 reaching a certain amount destroyed the continuity of the surface oxide layer,which accounted for the reduction of oxidation resistance of K4750 alloy at high temperatures.     

高度稳定化β型阻燃钛合金Ti40的氧化和氧化层剥落机理

对高度稳定化β型阻燃钛合金Ti40的氧化机理和氧化层剥落机理进行研究表明：合金氧化增重随温度升高明显增加,至1050℃反而降低;600℃的氧化膜主要为TiO2和V2O5,高于700℃氧化,因V2O5的挥发,氧化膜主要为TiO2,随温度升高,氧化物晶粒粗化,氧化膜疏松多孔,与基体黏附性降低,不低于900℃时开裂和剥落,不低于800℃氧化,氧化层疏松还存在SiO化合物,温度升高,SiO数量增多,由圆形球变为星形,至1050℃随氧化层剥落而消失;剥落后的基体氧化层仍为疏松状,有不连续分布的Cr2O3膜存在,同时还分析了Ti40合金不抗氧化的原因及氧化机理,提出了氧化机理模型。在分析氧化膜内应力产生及内应力释放机制基础上,提出了Ti40合金氧化层开裂、剥落机理。     

Al/Cr复合涂层对Ti2AlNb合金抗热腐蚀性能的影响

目的改善Ti2AlNb合金在高温腐蚀盐环境中的耐热腐蚀性能。方法在Ti2AlNb合金表面通过双层辉光等离子渗铬及磁控溅射镀铝技术制备Al/Cr复合涂层,分析涂层热腐蚀前后的微观形貌和物相组成,并探究涂覆Na2SO4盐膜的试样在不同温度下(750、850、950℃)的热腐蚀行为。结果Al/Cr复合涂层组织均匀致密,且与基体结合良好,厚度约73μm,由表及里依次由Al沉积层、Al/Cr合金层、Cr沉积层、Cr扩散层四部分组成。经不同温度Na2SO4盐热腐蚀后,Al/Cr复合涂层腐蚀程度均显著小于合金基体。涂层试样经750~850℃Na2SO4盐热腐蚀后质量变化较小,850℃腐蚀增重仅0.525 mg/cm^2,而经历950℃、40 h熔盐热腐蚀后失重达到73.571 mg/cm^2,且试样截面出现剥离、脱落现象,Al/Cr复合涂层抵抗热腐蚀能力减弱。结论具有涂层保护的试样抗热腐蚀性能明显优于合金基体。Al/Cr复合涂层在750~850℃Na2SO4盐环境中具有良好的热腐蚀抗力,而更高温度段(850~950℃)的热腐蚀抗力下降。Al/Cr复合涂层在Na2SO4盐环境中良好的抗热腐蚀性得益于涂层中Al、Cr元素氧化形成以Al2O3、Cr2O3为主的混合氧化膜,有效阻碍外界氧气及腐蚀性介质侵入基体。     

Microstructural Study of Fe-Cr-Al/Al Composite Coatings During Oxidation and Sulfidation at 900℃

The microstructure of a composite coating system,which was composed of an inner layer of Fe-Cr-Al and an outer layer of aluminum,was studied after it was respectively oxidized and sulfurdized at elevated temperatures. Apart from the Al2O3 scale formed on the surface,the microstructure of the composite coatings exposed at 900℃ in air for 4h was a three-layer structure. The first layer consisted of a solid solution of Cr and Fe in α aluminum and an intermetallic compound FeAl3,while the second layer was a single phase of the aluminide and the third layer still remained the same appearance as the original Fe-Cr-Al coating. The microstructural observation of the specimen tested at 850-900℃ at low oxygen pressure and high sulfur pressure for 576h revealed that the surface coatings of the specimen had transformed into a duplex structure containing an outer layer and a thicker aluminide layer beneath. X-ray diffraction results showed that the out layer was composed of Al2S3 and Al2O3 and that AlCrFe2 was the main phase composition of the aluminide layer,with a few of Al2S3 and Al2O3 accompanied.