棒线轧辊激光陶瓷合金化处理的应用实践

介绍大功率激光加工技术的基本原理及其性能特点，重点阐述了轧辊激光陶瓷合金化技术的原理及其性能特点。对棒线厂的应用工艺和效果进行了总结和探讨。     

铸铁轧辊激光合金化

在轧辊表面通过添加强碳化物形成元素,在适当的激光照射工艺条件下原位生成陶瓷相,得到以亚共晶组织为基,密集分布微米级陶瓷颗粒,同时保留较高残余奥氏体,形成强韧相间的激光合金化区.控制合金过程残余奥氏体量,可防止微裂纹的产生,在使用过程阻止裂纹的扩展.经过表层激光合金化处理的铸铁轧辊,过钢量可提高一倍以上.     

激光合金化技术提高轧辊寿命的研究

对75CrMo热带轧辊激光合金化工艺进行研究，探讨了合金化成分、激光工艺对轧辊性能的影响。结果显示：Co、W形成的化合物W3C、Co3W3C对轧辊硬度的提高有很大作用，但易产生裂纹。     

激光熔覆稀土陶瓷涂层进展

综述了激光熔覆稀土陶瓷涂层研究现状及其最新进展。介绍了激光熔覆工艺特点和影响因素,激光熔覆工艺包括粉末材料的加入方法和激光辐照加工。加入方法分预置法和同步送粉法,工艺参数包括光斑尺寸、扫描速度、熔覆道次、送粉量、涂层厚度和搭接量等。研究认为正确选择工艺参数是保证熔覆层质量和性能的关键。总结了稀土添加剂的强化作用机制,其主要作用为微合金化、净化晶界、细化晶粒、改善晶界状态、抑制柱状晶生长。对激光熔覆稀土陶瓷涂层研究的发展进行了展望。     

铝合金表面激光合金化Al-Nb金属间化合物涂层

铝铌合金是具有较高强度及硬度的结构材料和涂层材料。采用 2kW连续波Nd YAG激光在AA60 61Al合金表面制备Al Nb金属间化合物激光合金化改性层。采用功率密度 62 .5J·mm- 2 ,交互作用时间 0 .0 65s ,保护气氩气流量为 2 0L·min- 1 的激光辐照处理工艺 ,可获得无孔洞及裂纹、致密的Al Nb金属间化合物改性层。采用光学显微镜、扫描电子显微镜、能谱仪、X射线衍射仪及显微硬度计 ,研究改性层的表面组织形貌 ,成分分布、组织结构及硬度分布。     

铝合金/纳米碳管/钛复合层激光合金化组织

使用真空镀的方法在铝合金表面形成CNTs／Ti/Al/…多层复合，经激光合金化形成复合涂层。利用X射线衍射和扫描电镜对复合层的相构成及微观组织进行了分析。结果表明：铝合金表面复合层在激光合金化后存在着TiC颗粒和CNTs，TiC的含量随着激光功率的增加而增加；CNTs仍保留其原有的管状结构，且在复合层中相互缠绕呈网状均匀弥散分布；反应原位合成的TiC颗粒尺寸均匀细小，附着于CNTs上．从而改善了CNTs与基体之间的结合性能。     

激光表面合金化技术在中型轧辊上的应用

针对中型轧机轧辊的磨损问题,介绍了激光表面合金化技术在轧辊上的应用。采用激光表面合金化技术能显著降低了辊耗,提高孔型轧制吨位。     

激光特种合金化技术在棒材轧辊中的应用

针对激光特种合金化技术在棒材轧辊应用中存在的问题,通过采取增加表面粗糙度和表面堆焊及刻痕、不同工作面采用不同加工工艺、改进轧辊冷却水装置、优化轧槽修复量及单槽轧制量等措施,轧辊的使用寿命提高1倍以上,轧辊消耗降低10%。     

DB685钢板表面裂纹缺陷原因分析

用金相显微镜和扫描电镜分析方法,对DB685钢板表面裂纹进行分析。结果表明,钢板表面裂纹的形成与稀土氧化物有关。由于钢中稀土氧化物偏析于原奥氏体晶界上,弱化了晶界,造成钢板在轧制过程中产生裂纹。     

带钢涂层干燥用泡沫陶瓷红外辐射装置研究

本文针对带钢涂层干燥工艺的要求,研制了大型泡沫陶瓷燃气红外辐射装置,单台燃气红外辐射装置有效辐射面积为360 mm×360 mm,为了保证板面温度的均匀性,设计了专用的空燃气混合器和双层布风板.通过搭建燃烧实验平台对研制的燃烧装置进行实验,确定了稳定燃烧工况下相应的热负荷以及当量比范围,通过对实验结果的分析找到了最优泡沫陶瓷参数组合,并对实验过程中产生的燃烧不稳定现象以及实验结果对现有理论模型的修正作用进行了讨论.     

基于激光重熔的纳米陶瓷颗粒改性喷涂层的耐磨性研究

介绍了基于激光重熔技术的纳米陶瓷颗粒改性热喷涂耐磨涂层复合加工方法.以SiC纳米颗粒和WC-Co及Al2O3-TiO2热喷涂涂层为研究对象,进行了涂层改性加工试验.使用扫描电镜分析了纳米颗粒改性重熔涂层微观组织结构,并分别对热喷涂涂层、激光重熔喷涂涂层和纳米颗粒改性涂层进行了耐磨性测试.结果表明:SiC纳米颗粒能有效改善热喷涂涂层组织,并能显著提高涂层耐磨损性能.     

Elevated temperature oxidation of laser surface engineered composite boride coating on steel

The effects of long duration exposure of laser surface engineered composite boride coating on plain carbon steel in air at high temperatures were investigated in this study. Exposures at 600 °C, 800 °C, and 1000 °C for 10, 30, and 50 hours of composite-TiB₂ coated samples were conducted to study oxide scale growth and morphology. Kinetics of oxidation of the coating during elevated temperature exposures were separately studied using the thermogravimetric analysis (TGA) technique. The oxidation rate for all samples was parabolic in nature and the oxidation kinetic rate constant, K, increased with increasing temperature of exposure. Activation energy, Q for composite TiB₂ coating was found to be 205 kJ/mol. A thick (>35 μm) oxide layer formed for all duration of exposure at temperatures ≥800 °C. In case of 1000 °C exposure, a very thick (>150 μm) oxide layer was formed, which was separated from the substrate. X-ray diffractometry analysis revealed the complex nonstoichiometric nature of the oxides of type Ti _a O _b , Fe _m O _n , and Fe _x Ti _y O _z . Profilometric measurements indicated an increase in the surface roughness of the oxide layer with an increase in temperature of exposure. These physical observations indicated that the nature and morphology of the oxides formed at various temperatures and duration of exposure are complex.     

退火工艺对高耐蚀Galvalume钢板镀层表面结构的影响

采用连续退火、镀锌和合金化模拟机制取了不同退火温度和退火时间条件下Galvalume钢板的退火试样,通过SEM、EDS、XRD等试验方法,进行了退火工艺对于Galvalume钢板镀层表面结构影响研究,阐明了表面相结构和w（Fe）的变化规律。结果表明,随着退火温度和退火时间的增加,Galvalume镀层表面α相和α＋β共...     

Effect of surface roughness on the surface lubrication performance of galvanized steel sheets with a self-lubricated coating

Four kinds of galvanized steel sheets having different surface roughness values were used to prepare the steel sheets with a self-lubricated coating.The effects of surface roughness on the surface lubrication performance of the steel sheets were examined using a friction coefficient tester.Results revealed large dynamic friction coefficients for the galvanized steel sheets,which increased remarkably with surface roughness.Once the self-lubricated coating was applied,significant drops in the dynamic friction coefficients were measured.After the first stage of the friction test,the coefficients were almost unchanged,which reflected a weak dependence on the surface roughness of the self-lubricated steel sheets.However,the dynamic friction coefficients gradually increased as the test progressed,where these increase clearly correlated with the surface roughness of the self-lubricated steel sheets.     

Laser rapid manufacturing of bi-metallic tube with Stellite-21 and austenitic stainless steel

Fabrication of multi-material engineering components is one of the technologies to address diverse and conflicting functional requirements posed by rapid technological development. Bi-metallic tube is one such multi-material component with different materials on internal and outer surfaces. This paper briefs about fabrication of a bi-metallic tubular structure with an indigenously developed 3.5 kW CO₂ laser integrated with a beam delivery system, a 5-axis CNC work station along with a powder feeding sub-system. The bi-metallic tube was fabricated with cobalt based alloy Stellite 21 on inner diameter and type 316L stainless steel on the outer diameter. Besides, a stainless steel tube with an internal step of Stellite 21 was also fabricated. As-fabricated bi-metallic structure was structurally sound and carried desired transition in chemical composition and hardness across its wall thickness.     

Processing and characterization of plasma-sprayed ceramic coatings on steel substrate: Part II. On coating performance

This investigation envisages the performance evaluation of a series of plasma-sprayed coatings from a few inexpensive powders, namely, alumina, plasma dissociated zircon (PDZ), zircon sand, and zircon-20 wt pct calcia. The hardness and adhesion (bond) strength of the coatings have been evaluated. All coatings offer an attractive thermal fatigue property. An added layer of yttria between the top and bond coats improves the thermal fatigue resistance appreciably. The wear performance of these coatings has also been evaluated using a “pin-on-disc” type wear testing setup. The Indian alumina coating offers a superior wear resistance and thermal fatigue property compared to an imported alumina coating. The coatings based on zirconia-silica offer an attractive thermal fatigue resistance along with an acceptable wear resistance. The latter improves considerably upon annealing of the coatings because of the removal of the residual stresses accumulated during deposition. Among these zirconia-silica-based coatings, the zircon-20 wt pct calcia is the most promising. The finishability of these coatings has been studied using a surface grinding setup equipped with a diamond wheel. The cutting forces and the surface roughness of the ground surface have been measured. The coatings have been found to possess a reasonably good grindability.     

Processing and characterization of plasma-sprayed ceramic coatings on steel substrate: Part I. On coating characteristics

This investigation envisages the processing of a series of plasma-sprayed coatings from a few commercially available and inexpensive powders, namely, alumina (commercial grade, Indian), plasma-dissociated zircon (PDZ), zircon sand, and zircon-20 wt pct calcia. These powders do not belong to the so-called “plasma sprayable” grade, expensive powders. The microstructures and several properties of these coatings have been studied to evaluate their potential as thermal barrier and wear-resistant coatings. With an appropriate choice of processing condition, a sound and adherent ceramic coating is achievable using such powders. In some coatings, a layer of yttria has been applied between the top and bond coats with an aim to improve its thermal barrier properties. Such a layer does not disrupt the interfacial continuity of the coatings. The powders have been found to undergo phase transformations during spraying, subsequent annealing, and also during tribological testing of the coatings. An understanding of such phase transformations is important for the interpretation of coating behavior during performance tests as wear-resistant and thermal barrier coatings. These responses are dealt with in Part II of this series of articles.     

火花源发射光谱法测定钢中稀土总量

提出了利用火花源光谱仪分析钢中稀土元素的分析方法。验证了用轻稀土代表稀土总量的可行性 ,确定了制样条件 ,校正了共存元素的干扰 ,分析的重复性均在GB/T2 2 3 49-94的规定范围内 ,分析周期小于 8min。