高炉热风炉用高发射率涂料的节能效果及机理分析

为研究高发射率涂料在高炉热风炉蓄热室内的应用效果,应用数学模拟和工业试验对比的研究方法对节能效果进行了分析.结果表明:模拟结果接近工业应用数据,可以定量地说明涂料对热风炉传热过程的积极作用;应用高发射率涂料后,可使高炉热风炉热风温度升高25℃,烟气温度降低13℃.结合数学模拟和工业热诊断结果,对涂料在热风炉内使用的节能机理进行了分析.认为在格子砖表面涂覆高发射率涂料,在燃烧期会使蓄热体内烟气与格子砖辐射换热加强,格子砖表面温度增加,且使蓄热体蓄热量增加.模拟结果表明:烟气中CO2成分对提高辐射传热起重要作用;CO2体积分数平均每提高5%,则热风温度提高6～8℃.     

Microstructure and properties of sputtered thermal barrier coatings

A 3 kW radio frequency (RF) magnetron-sputtering unit was used to produce zirconia ceramic coatings on hollow turbine blades and vanes, which had been deposited a NiCrAlY bond coat layer by cathodic arc deposition. The NiCrAlY coating surface was shot-peened, and the residual stress in the bond coat layer and the effects of heat treatment on the residual stress are presented.After shot peening porosities and microgaps disappear in the NiCrAlY bond coat, the whole depth profile is residual compressive stress. Coarseness tests show that the roughness value (Rz) decreases from 16.4 to 3.3 μm. The microstructure and phase composition of the coatings were investigated using electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results show that the NiCrAlY bond coat is composed of γ' and Cr phases, and the Al₂O₃ scales are formed near the interface between the ZrO₂ ceramic layer and the NiCrAlY bond coat. No degradation occurred to RF sputtered ceramic coatings after oxidating at 1150℃ for 100 h,heating at 1150℃ for 5 min and then air-cooling for 500 thermal cycles.     

Microstructure and mechanical properties of titanium nitride coatings for cemented carbide cutting tools by pulsed high energy density plasma

Hard, wear-resistant and well-adhesive titanium nitride coatings on cemented carbide cutting tools were prepared by the pulsed high energy density plasma technique at ambient temperature. The results of Auger spectra analysis indicated that the interface between the coating and substrate was more than 250 nm. Under optimized deposition conditions, the highest critical load measured by nanoscratch tester was more than 90 mN, which meant that the TiN film was well adhesive to the substrate; the highest nanohardness and Young抯 modulus according to nanoindentation tests were near to 27 and 450 GPa. The results of cutting tests evaluated by turning hardened CrWMn steel in industrial conditions indicated that the wear resistance and edge life of the cemented carbide tools were enhanced dramatically because of the deposition of titanium nitride coatings. These improvements were attributed to the three combined effects: the deposition and ion implantation of the pulsed plasma and the becoming finer of the grain sizes.     

MoCrFeMnNi高熵合金退火后的组织和性能

高熵合金因具有高强度、耐腐蚀、耐高温氧化等优异的性能而备受关注.采用铝热反应法制备MoCrFeMnNi高熵合金,用XRD、SEM、EDS、显微硬度和压缩实验研究了铸态及700 ℃/12 h、800 ℃/6 h、1 000 ℃/3 h退火后合金的组织和性能变化.结果表明:铝热法制备的MoCrFeMnNi高熵合金为典型的枝晶形貌,晶体结构主要由BCC相、FCC相以及少量的σ相构成,其中枝晶区域为BCC结构,富含Mo和Cr元素;枝晶间区域为FCC结构,富含Ni元素.随着退火温度的上升,枝晶间逐渐析出纳米级σ相,使得合金硬度上升,在800 ℃/6 h退火处理后达到667 HV,抗压强度达到1 050 MPa;1 000 ℃/3 h退火后,σ相团聚成球状和针状并在高温下部分溶解,σ相的减少使得合金硬度下降,抗压强度与铸态时相当,塑性显著提升.     

电弧喷涂药芯丝材涂层的组织和高温冲蚀性能

采用电弧喷涂自制的FeB和CrB两种药芯丝材在20#钢基体表面制备了FeB涂层和CrB涂层,分析了两种涂层的显微组织、相结构、硬度和孔隙率,并采用高温冲蚀磨损试验考察了其耐高温冲蚀磨损性能.结果表明:FeB涂层主要物相是α-Fe,FeB和FeB2,CrB涂层中主要存在α-Fe,CrB和Cr2O3相,两者的微观组织结构都是由弥散分布在铁基金属中间的硬质相粒子和少数孔洞组成,涂层与基体之间结合良好.FeB涂层的孔隙率小于CrB涂层,但硬度低于CrB涂层.FeB涂层和CrB涂层在650 ℃下具有良好的抗高温冲蚀磨损性能,都能够对20#钢基体起到较好的防护作用,但CrB涂层抗高温冲蚀磨损性能比FeB涂层更好.     

反应超音速火焰喷涂TiC-TiB2-Ni涂层的组织性能

基于反应超音速火焰喷涂技术,以钛粉、炭化硼、石墨和镍粉为原材料,在45#钢基体上制备3种TiC-TiB2-Ni涂层,并对涂层组织与相关性能进行研究.结果表明:Ti-B4C-C-Ni粉末组元在喷涂过程中发生剧烈的放热反应,可以合成TiC-TiB2-Ni金属陶瓷涂层,Ti-B4C之间发生反应的趋势和剧烈程度明显大于Ti-C之间的;涂层中除主要组成相TiC,TiB2和Ni外,还含有一定量的Ti(C,N),TiO2,Ti2O3和NiO相;随着TiB2含量的减少,涂层中的气孔和夹杂物含量增多,显微硬度和结合强度逐渐降低,滑动磨损量明显升高,涂层耐磨性能下降;利用Ti-B<4>C-Ni材料组元制备的TiC-TiB2-Ni涂层的性能最优,涂层的滑动磨损失效形式主要表现为脆性剥落和犁削.     

600 MPa级钛微合金化高强钢的组织与性能研究

采用光学显微镜、透射电镜以及能谱分析等对转炉CSP流程600 MPa级钛微合金化高强钢的组织及性能进行研究.结果表明,试验钢具有良好的综合力学性能,其典型组织为多边形铁素体加粒状贝氏体;位错和位错胞的强化作用成为钛微合金钢的主要强化机制之一;钢中M/A岛在增加试验钢强度的同时并未明显降低其韧性和塑性;试验钢中存在TiN、TiC和TiS等析出物,为钢的细晶强化和析出强化提供了保证;试验钢中存在大量纳米级铁碳析出物,其沉淀强化作用不容忽视.     

等温淬火高硅铸钢的显微组织和机械性能

为开发一种新型高硅耐磨铸钢 ,采用扫描电子显微镜研究了不同等温温度下高硅铸钢的显微组织 ,对不同等温温度下高硅铸钢的抗拉强度、冲击韧性和硬度进行了系统研究。结果表明 ,高硅铸钢经等温淬火热处理后 ,在较大的温度范围 (2 4 0～ 4 0 0℃ )内都可以得到单一的由贝氏体铁素体和富碳的残余奥氏体交替排列的奥贝双相组织 (Ausferrite) ,组织中没有碳化物析出。在 2 80～ 3 60℃范围内等温 ,可以获得强度、韧性、硬度配合良好的双相组织。高硅铸钢具有优异的综合机械性能 ,同时具有良好的冷作硬化能力     

等离子喷涂钼基非晶纳米晶复合涂层的组织和电化学特性

用Mo基合金粉末(含Si,B,Cr,W,Mo,Ni等)作为喷涂材料,利用大气等离子喷涂(APS)技术,在0Cr13Ni5Mo不锈钢基体上制备了钼基非晶纳米晶复合涂层.利用XRD观察了涂层的晶型结构,扫描电镜(SEM)观察涂层的组织形貌,恒电位扫描仪对涂层的电化学特性进行了测试,显微硬度仪测量涂层的显微硬度.实验结果表明,利用等离子喷涂工艺可以制备高硬度的Mo基非晶纳米晶复合涂层,这种涂层结构均匀致密,其显微硬度最高达到1 426.9HV.孔隙率约为5.5%.非晶纳米晶复合涂层在3.5%NaCl溶液中存在钝化现象,自腐蚀电流为6.459μA·cm-2,腐蚀速度0.869 mm·a-1.     

Design and calculation of low infrared transmittance and low emissivity coatings for heat radiative applications

The infrared transmittance and emissivity of heat-insulating coatings pigmented with various structural particles were studied using Kubelka-Munk theory and Mie theory. The primary design purpose was to obtain the low transmittance and low emissivity coatings to reduce the heat transfer by thermal radiation for high-temperature applications. In the case of silica coating layers constituted with various structural titania particles (solid, hollow, and core-shell spherical), the dependence of transmittance and emissivity of the coating layer on the particle structure and the layer thickness was investigated and optimized. The results indicate that the coating pigmented with core-shell titania particles exhibits a lower infrared transmittance and a lower emissivity value than that with other structural particles and is suitable to radiative heat-insulating applications.     

新型高强高韧铝镁硅合金的组织和性能

在6063合金基础上设计出一种新的Al-Mg-Si系合金.合金经熔炼铸造和挤压加工后分别进行退火、自然时效、人工时效处理,优化自然时效时间,并利用金相显微镜、X线衍射仪、扫描电镜及电子万能实验机对合金微观组织、断口形貌和力学性能进行检测分析.研究结果表明:新合金与6063合金相比具有更高的强度和塑性,人工时效态抗拉强度和伸长率分别达到314.32 MPa和19.63%,自然时效态抗拉强度、伸长率分别为277.26 MPa和28.61%(稳定值);新合金最佳自然时效时间为72 h.     

Microstructure and mechanical properties of twin-wire arc sprayed Ni-Al composite coatings on 6061-T6 aluminum alloy sheet

We have systematically studied the microstructure and mechanical properties of Ni-5wt%Al and Ni-20wt%Al composite coatings fabricated on 6061-T6 aluminum alloy sheet by twin-wire arc spraying under different experimental conditions. The abrasive wear behavior and interface diffusion behavior of the composite coatings were evaluated by dry/wet rubber wheel abrasive wear tests and heat treatment, respectively. Experimental results indicate that the composite coatings exhibit features of adhesive wear. Besides, the Vickers microhardness of NiAl and Ni₃Al intermetallic compounds is relatively larger than that of the substrate, which is beneficial for enhancing the wear resistance. With the increase of annealing temperature and time, the interface diffusion area between the Ni-Al coating and the substrate gradually expands with the formation of NiAl₃ and Ni₂Al₃ phases, and is controlled by diffusion of aluminum atoms. The grain growth exponent n of diffusion kinetics of the Ni-Al coating, calculated via a high-temperature diffusion model at 400, 480, and 550℃, is between 0.28 and 0.38. This satisfies the cubic law, which is consistent with the general theoretical relationship of high-temperature diffusion.     

截齿用新型高硅低碳空冷贝氏体钢的组织与性能

为了克服常用 35 Cr Mn Si截齿原材料价格高、热处理工艺复杂、耗能大、污染环境、寿命低等缺点 ,设计了适合采煤机截齿用的高硅新型低碳空冷贝氏体钢 ,其成分 (质量分数 ,10 0× w) C为 0 .19～ 0 .2 7,Mn为 2 .0～ 4.0 ,B为0 .0 0 15～ 0 .0 0 3,Si为 0 .7～ 1.6。较高的硅含量提高了 Mn-B系贝氏体钢的空冷淬透性和韧性 ,较低的含碳量极大地提高了截齿的韧性和抗断裂能力。此钢经 116 3K奥氏体化后空冷 ,即可获得具有良好的高硬度、高韧性配合的贝氏体或贝氏体 /马氏体复相组织 ,其各项力学性能指标均达到或超过了采煤机截齿技术标准中的要求。新型空冷低碳贝氏体钢截齿 ,采用空冷硬化 ,工艺简单 ,免除了盐浴等温淬火 ,节约了能源 ,降低成本约 10 % ,并减少了污染。现场试验结果表明 :新型空冷低碳贝氏体钢截齿万吨耗齿量为 12 4件 ,齿体无弯曲和折断 ,比原 35 Cr Mn Si截齿可降低齿耗 8.8%左右     

铜基复合发光涂层组织及其摩擦磨损性能

利用真空热压烧结技术以铜粉、铜铝混合粉、高铝青铜合金粉和磷光粉体SrAl2O4∶Eu2+,Dy3+、Ba Al2O4∶Eu2+,Dy3+为原料分别制备纯铜、铜铝和高铝青铜系列的铜基复合发光涂层,采用MMW-1A型摩擦磨损试验机测试磷光颗粒掺杂的不同铜基复合涂层的摩擦磨损性能;采用扫描电子显微镜分析摩擦前后复合涂层磨损表面形貌.结果表明:磷光颗粒在3种复合涂层中都是均匀分布于涂层中,与各基体之间形成机械结合;硬质磷光颗粒可以显著增强铜铝基复合发光涂层和高铝青铜基复合发光涂层的耐磨性,其中高铝青铜基复合发光涂层摩擦磨损性能、磨损表面组织均优于铜铝基复合发光涂层,高铝青铜基复合发光涂层的磨损机制主要为磨粒磨损.     

碳氮强化电弧喷涂涂层合金组织与耐磨性能

研制一种新型的碳氮合金化喷涂丝材,通过高速电弧喷涂设备在Q235低碳钢板表面制备耐磨合金。用扫描电镜观察合金涂层形貌,用EDS分析涂层化学成分,并用显微硬度仪检测涂层显微硬度及磨粒磨损试验机测量涂层磨损失重。研究涂层的成形、耐磨损性能及其机制。结果表明:使用添加N替代部分C进行碳氮强化的喷涂丝材所制备的涂层合金成形良好,涂层组织均匀,结构致密;涂层显微硬度平均值为568HV0.1,最高值达593HV0.1;涂层结合强度达到45.8MPa; 细小的碳氮化物硬质相颗粒使涂层具有良好的耐磨损性能,其耐磨性是4Cr13不锈钢涂层的1.58倍。     

Microstructure characteristics of Ni/WC composite cladding coatings

A multilayer tungsten carbide particle (WCp)-reinforced Ni-based alloy coating was fabricated on a steel substrate using vacuum cladding technology. The morphology, microstructure, and formation mechanism of the coating were studied and discussed in different zones. The microstructure morphology and phase composition were investigated by scanning electron microscopy, optical microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. In the results, the coating presents a dense and homogeneous microstructure with few pores and is free from cracks. The whole coating shows a multilayer structure, including composite, transition, fusion, and diffusion-affected layers. Metallurgical bonding was achieved between the coating and substrate because of the formation of the fusion and diffusion-affected layers. The Ni-based alloy is mainly composed of γ-Ni solid solution with finely dispersed Cr₇C₃/Cr₂₃C₆, CrB, and Ni+Ni₃Si. WC particles in the composite layer distribute evenly in areas among initial Ni-based alloying particles, forming a special three-dimensional reticular microstructure. The macrohardness of the coating is HRC 55, which is remarkably improved compared to that of the substrate. The microhardness increases gradually from the substrate to the composite zone, whereas the microhardness remains almost unchanged in the transition and composite zones.     

Microstructure and mechanical properties of Ni-based composite coatings reinforced by in situ synthesized TiB2 + TiC by laser cladding

A Ni-based composite coating reinforced by in situ synthesized TiB₂ and TiC particles was fabricated on Ti6Al4V by laser cladding. An attempt was made to correlate the thermodynamic predictions and experimental observation. The microstructure and the microhardness profile across the coating were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and a hardness tester. It is found that the coating mainly consists of a large number of reinforcements (black blocky TiB₂, flower-like or equiaxial TiC, and fine acicular CrB) and the γ matrix. The hardness of TiB₂, TiC, and CrB reinforcements is much higher than that of the γ matrix. The dispersive distribution of such high hardness reinforcements causes the increase in hardness of the whole coating. The average value of the hardness is approximately Hv_0.2 700 in the coating. The hardness of the coating is obviously higher than that of the substrate due to the dispersion strengthening of reinforcements.     

甘蔗渣基木陶瓷的结构及性能试验

应用不同质量比的甘蔗渣和环氧树脂进行复合、热压,经真空烧结后,制得甘蔗渣基木陶瓷.利用TG-DSC对甘蔗渣基木陶瓷的热分解行为进行初步分析,利用XRD,SEM表征了所制备的木陶瓷的相组成和微观结构,研究了甘蔗渣用量对开口气孔率及摩擦性能的影响.结果表明:甘蔗渣基木陶瓷具有生物管状的多孔结构;随着甘蔗渣用量的降低,木陶瓷的石墨化程度略有提高;木陶瓷的开口气孔率随甘蔗渣用量减少而减小;摩擦系数随转速的增加而增大,随载荷的增大而减小.当甘蔗渣/环氧树脂质量比为1∶1时,木陶瓷的开口气孔率为35.12%,摩擦性能最好.