功率对激光熔覆(Fe0.25Co0.25Ni0.25Cr0.125Mo0.125)86B14涂层组织均质性及磨损性能的影响

目前激光熔覆缺少对涂层组织、相结构纵向均质性与性能关联的研究。采用激光熔覆技术,选取不同的激光功率,制备(Fe_0.25Co_0.25Ni_0.25Cr_0.125Mo_0.125)₈₆B₁₄高熵合金涂层;借助电子探针(EPMA)、扫描电子显微镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)等观察涂层微观组织与物相纵向分布,利用显微硬度计和摩擦磨损试验机测试涂层不同深度部位显微硬度及磨损性能,分析激光功率对熔覆(Fe_0.25Co_0.25Ni_0.25Cr_0.125Mo_0.125)₈₆B₁₄涂层纵向组织、物相分布影响规律及磨损性能。结果表明：三种功率下,涂层均由BCC+FCC相、硬质相Mo2B组成,Mo2B在枝晶间富集。随着功率的增加,涂层中底部显微组织由细枝晶向粗大的柱状晶转变。三种涂层硬...     

激光熔覆CoCrNiMnTix高熵合金涂层组织及耐磨性能研究

目的 针对高铁制动盘等高速强力磨损的关键件,设计激光熔覆CoCrNiMnTix高熵合金涂层,提高表面的硬度和耐磨性。方法 采用激光熔覆技术在Q235钢表面制备CoCrNiMnTix高熵合金涂层,利用XRD和SEM对涂层微观组织进行表征,通过显微硬度计和纳米压痕仪测试涂层硬度,运用摩擦磨损试验机和三维形貌仪研究涂层的摩擦磨损性能。结果 在激光熔覆CoCrNiMnTix涂层中,随着Ti含量的增加,涂层物相由单一的FCC相转变为FCC+Laves相。由于固溶强化以及Laves相含量增多,涂层的显微硬度不断提高,CoCrMnNiTi硬度达到523HV0.1,最高纳米硬度达到6.91 GPa。CoCrNiMnTix系涂层的弹性模量大小相近。随着Ti含量的增加,涂层的耐磨性呈现升高趋势,当Ti的摩尔分数增加至0.75时,涂层具有最好的耐磨性,但进一步增加Ti含量时,由于脆硬性的Laves相逐渐增多,磨损形式由低Ti含量时的粘着磨损逐渐转变为高Ti含量时的磨粒磨损,使涂层耐磨性能下降。结论 激光熔覆CoCrMnNiTix涂层可以显著提高基体的耐磨性,Ti的摩尔分数为0.75时,在FCC基体中形成了少量Laves相,既提高硬度,又实现强韧配合,涂层表现出最佳的耐磨损性能。     

激光熔覆制备高熵合金涂层的研究进展

激光熔覆技术具有高的冷却速度、低的稀释率、涂层与基体冶金结合等优点,采用激光熔覆技术制备耐磨性和耐腐蚀好的高熵合金涂层是近几年高熵合金领域的研究热点之一。首先概括了激光熔覆技术制备的高熵合金体系及组织结构特征,大多高熵合金涂层以固溶相为主,少数合金涂层形成了非晶相,与熔炼制备高熵合金块体材料相比,涂层组织具有均匀、细小致密等特点。然后介绍了涂层的性能特征,涂层具有较高的硬度、良好的耐磨性,同时指明高耐磨性涂层不仅具有高的硬度,同时还需要具有一定的塑韧性。涂层合金中大多包含有Al、Cr、Si和Co等形成稳定氧化膜的元素,呈现优异的抗腐蚀性能。随后重点概述了合金元素（Al、Mo、V、Ti、B、Ni、Nb和Cu等）、熔覆工艺参数（激光功率、扫描速度和预制层粉末厚度）和热处理工艺对涂层组织结构和性能的影响规律。其中,熔覆工艺参数对涂层组织结构和性能的影响研究相对较少,将是未来研究的重点内容之一。最后对激光熔覆技术制备高熵合金涂层存在的问题和未来的研究方向做了展望。     

Si 含量对 FeCoCr0. 5 NiBSix 高熵合金涂层组织结构和耐磨性的影响

目的研究Si含量对激光熔覆FeCoCr_(0.5)NiBSi_x高熵合金涂层组织结构、硬度和耐磨性的影响。方法采用激光熔覆技术,在45钢基体表面制备了不同Si含量的FeCoCr_(0.5)NiBSi_x(x取0,0.1,0.2,0.3,0.4)系列高熵合金涂层,分析涂层的宏观形貌、微观组织及相结构,测试涂层的硬度,通过摩擦磨损实验测试涂层的耐磨性。结果熔覆态高熵合金涂层均由FCC相和M2B相组成,显微组织包括先共晶组织和共晶组织。随着Si含量的增加,FCC相增多,M_2B相减少,共晶组织由蜂窝状到颗粒状,然后消失。高熵合金涂层的平均硬度随着Si含量的增加而先降低后增加,FeCoCr_(0.5)NiBSi0.3的硬度值最小(613HV),FeCoCr_(0.5)NiBSi_(0.4)的硬度值最高(820HV)。高熵合金涂层的磨损体积随着Si含量的增加而先增大后减小,FeCoCr_(0.5)NiBSi_(0.3)的磨损体积最大(0.00406mm3),FeCoCr_(0.5)NiBSi0.4的磨损体积最小(0.00233mm3)。结论随着Si含量增加,涂层的M2B相减少,共晶组织逐步消失,耐磨性则先降低后提高。耐磨性能最好的是FeCoCr_(0.5)NiBSi_(0.4)高熵合金涂层。     

热处理对激光熔覆CoCrFeNiSi2.0高熵合金涂层组织与性能的影响

目的 探究热处理温度对激光熔覆CoCrFeNiSi2.0高熵合金组织、物相、显微硬度及摩擦磨损性能的影响,为研究提高高熵合金性能的工艺流程提供参考。方法 采用激光熔覆技术制备了CoCrFeNiSi2.0高熵合金,利用高温炉加热方法对制得涂层进行不同温度(热处理温度分别为600、800、1 000 ℃)的热处理,30 min分别升温至600、800、1 000 ℃,保温30 min,后随炉冷却至室温。采用显微硬度仪、真空摩擦磨损试验机、Leica DVM6光学显微镜、扫描电镜(SEM)、X射线衍射仪(XRD)等设备对涂层的显微硬度、摩擦磨损性能、显微组织、物相组成进行分析研究。结果 未经热处理原始试样高熵合金涂层物相组成主要为BCC相,同时夹杂少量的(Fe,Mn)2SiO4相,经过不同温度的热处理后,(Fe,Mn)2SiO4逐渐分解,1 000 ℃热处理后完全消失;Cr2Si、Ni4Si相析出且在一定温度范围内随热处理温度上升含量逐渐增加,BCC相衍射峰高度随着热处理温度的增加先升高后降低。结论 热处理温度不同会影响涂层综合性能的改变,热处理温度为800 ℃时合金的综合性能优于原始试样涂层,内部组织较为均匀,Cr2Si、Ni4Si等析出相含量最多且均匀分布在晶界处,涂层显微硬度最高达1 347.4HV0.3,摩擦因数基本稳定在0.19。当热处理温度达到1 000 ℃时,CoCrFeNiSi2.0高熵合金涂层呈单一的BCC相,这势必会对涂层性能产生一定影响。     

合金组元与含量对激光熔覆高熵合金涂层的影响研究综述∗

高熵合金被视为是近年来合金化理论的一次创新,打破了传统合金以一种或两种金属元素为主元的设计理念,将合金设计体系扩展到以五种及以上元素为主元的领域,由于能够组成高熵合金的元素种类繁多且含量可调,所以具有巨大的开发潜力。 激光熔覆技术作为一种先进的新型材料表面改性技术与装备维修技术,与高熵合金结合,可为该合金材料的应用开辟出新的空间。 通过对现有研究梳理,归纳总结激光熔覆高熵合金涂层的耐腐蚀性能、硬度与摩擦磨损性能以及抗高温氧化性能的性能强化机理;概括分析常见高熵合金的组成元素及其含量变化,对激光熔覆技术制备合金涂层组织结构和性能的影响,为高熵合金涂层组元的选取提供借鉴参考。 最后指出激光熔覆高熵合金涂层在当前研究中的不足与仍需深入研究的问题,展望了高熵合金的应用前景与未来的研究方向。 系统梳理 Al、Ti、Nb、Mo、Ni、Si、B、C 等合金化元素对激光熔覆技术制备高熵合金涂层组织结构和性能的影响规律和作用效果,为激光熔覆高熵合金涂层的合金分成设计提供理论指导。     

激光熔覆MoFeCrTiWSix多主元合金涂层组织和性能研究

在Q235钢表面激光熔覆制备了MoFeCrTiWSi_x(x=0,0.2,0.4,0.6,0.8,1.0)多主元合金涂层,采用X射线衍射仪(XRD)、扫描电镜(SEM)和硬度计等系统研究了Si对涂层的组织、相结构、显微硬度及高温抗氧化性能的影响。结果表明:激光熔覆MoFeCrTiW多主元合金涂层为简单bcc结构,组织为等轴晶。添加Si后,涂层主体相仍为bcc结构,当x≥0.4后,会有少量金属间化合物生成,合金涂层由先共晶bcc相和共晶组织(bcc相+Cr5Fe50Mo8.9Si5.2Ti20.4相)组成,随着Si量的增加,先共晶相的形态由胞状树枝晶转变为柱状树枝晶和等轴树枝晶,共晶组织逐渐增多。涂层从表面至结合区的混合熵呈高熵-中熵变化。涂层硬度和900℃时的抗氧化性能随着Si含量的增加有所提高,当x=1时,涂层平均硬度及抗氧化性能最高。     

激光熔覆高熵合金涂层的耐腐蚀性能研究进展

利用激光熔覆技术制备的高熵合金涂层已成为一种新兴的绿色清洁耐腐蚀涂层.为了最大程度发挥高熵合金涂层的耐腐蚀防护性能,需要探究激光熔覆高熵合金涂层耐腐蚀性能的影响因素及影响机理.首先阐述了高熵合金理论以及利用激光熔覆技术制备高熵合金涂层的优势,总结了高熵合金激光熔覆涂层优异耐腐蚀特性及耐腐蚀强化机理.重点综述了高熵合金元素组成、激光熔覆工艺参数、涂层后处理工艺以及服役温度4个因素,对高熵合金激光熔覆涂层耐腐蚀性能的影响规律与影响机理.高熵合金中适当添加Ni、Al、Ti等元素,在一定程度上可以提高涂层的耐腐蚀性,但是随着元素含量的进一步增加,由于高熵合金涂层的物相组成改变、晶格畸变严重、元素偏析加剧,可能导致涂层的耐腐蚀性能降低.适宜的激光加工参数可以使涂层具有较好的耐腐蚀性,原因在于涂层的缺陷较少、组织细密均匀.退火、激光重熔、超声冲击处理等涂层后处理工艺,通过改变高熵合金涂层的物相组成以及微观组织特征,来提高其耐腐蚀性.激光熔覆高熵合金涂层的服役环境温度越高,则腐蚀速率越快.最后,对激光熔覆高熵合金涂层的耐腐蚀性能强化方法进行了总结与展望.     

激光熔覆制备高熵合金涂层的研究进展

介绍了传统高熵合金制备方法的局限性和激光熔覆技术的优势,主要从硬度、耐磨性、耐蚀性、高温性能、磁性能、电阻性能以及储氢性能方面综述了目前激光熔覆技术制备高性能高熵合金涂层的研究现状。展望了激光熔覆高熵合金涂层的应用前景和研究方向。     

高熵合金涂层的研究进展

高熵合金涂层在工程实际应用中较传统合金具有良好的前景,对近年来高熵合金涂层的研究进展进行了概述。首先对制备高熵合金涂层的表面熔覆技术进行详细的介绍,其中包括激光熔覆技术、等离子熔覆技术、氩弧熔覆技术,分析了各表面熔覆技术的优缺点;然后总结了高熵合金涂层的组织及性能特征,涂层中相的组成包括:固溶体相、金属间化合物、纳米析出相、非晶相;性能上,高熵合金涂层由于各种效应的作用,具有高强度及硬度、优异的耐磨性、良好的耐腐蚀性及高温抗氧化性等一系列优异的性能;而后进一步分析了表面熔覆技术工艺参数对高熵合金涂层质量的影响规律、合金元素对高熵合金涂层性能的影响及热处理对高熵合金涂层相组织演变的影响;最后对高熵合金涂层的应用前景及其未来的研究方向进行展望。     

Cutting performance and failure mechanisms of an Al2O3/WC/TiC micro- nano-composite ceramic tool

An Al₂O₃-based composite ceramic tool material reinforced with WC microparticles and TiC nanoparticles was fabricated by using hot-pressing technique. The cutting performance, failure modes and mechanisms of the Al₂O₃/WC/TiC ceramic tool were investigated via continuous and intermittent turning of hardened AISI 1045 steel in comparison with those of an Al₂O₃/(W, Ti)C ceramic tool SG-4 and a cemented carbide tool YS8. Worn and fractured surfaces of the cutting tools were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results of continuous turning revealed that tool lifetime of the Al₂O₃/WC/TiC ceramic tool was higher than that of the SG-4 and YS8 tools at all the tested cutting speeds. As for the intermittent turning, tool life of the Al₂O₃/WC/TiC ceramic tool was equivalent to that of YS8, but shorter than that of the SG-4 at lower cutting speed (110 m/min). However, tool life of the Al₂O₃/WC/TiC ceramic tool increased when the cutting speed increased to 170 m/min, becoming much longer than that of the SG-4 and YS8 tools. The longer tool life of the Al₂O₃/WC/TiC composite ceramic tool was attributed to its synergistic strengthening/toughening mechanisms induced by the WC microparticles and TiC nanoparticles.     

Failure mechanisms of TiB2 particle and SiC whisker reinforced Al2O3 ceramic cutting tools when machining nickel-based alloys

In this paper, Al₂O₃/TiB₂/SiC_w ceramic cutting tools with different volume fraction of TiB₂ particles and SiC whiskers were produced by hot pressing. The fundamental properties of these composite tool materials were examined. Machining tests with these ceramic tools were carried out on the Inconel718 nickel-based alloys. The tool wear rates and the cutting temperature were measured. The failure mechanisms of these ceramic tools were investigated and correlated to their mechanical properties. Results showed that the fracture toughness and hardness of the composite tool materials continuously increased with increasing SiC whisker content up to 30 vol.%. The relative density decreased with increasing SiC whisker content, the trend of the flexural strength being the same as that of the relative density. Cutting speeds were found to have a profound effect on the wear behaviors of these ceramic tools. The ceramic tools exhibited relative small flank and crater wear at cutting speed lower than 100 m/min, within further increasing of the cutting speed the flank and crater wear increased greatly. Cutting speeds less than 100 m/min were proved to be the best range for this kind of ceramic tool when machining Inconel718 nickel-based alloys. The composite tool materials with higher SiC whisker content showed more wear resistance. Abrasive wear was found to be the predominant flank wear mechanism. While the mechanisms responsible for the crater wear were determined to be adhesion and diffusion due to the high cutting temperature.     

不同碳/氮比的Ti(C x , N1- x )基金属陶瓷的显微组织与性能

Ti(C_x,N_1-x)基金属陶瓷是用不同碳氮比制造的。研究了碳/氮比对芯-环结构和金属陶瓷性能的影响。结果表明，由于孔太多， Ti(C_0.5,N_0.5)基金属陶瓷的性能较差。随着碳/氮比的增加，白核/灰环的形成率降低，并且微观结构的均匀性增强。因此，基于 Ti(C_0.7,N_0.3)的金属陶瓷显示出优异的力学性能，但有少量的孔隙和较低的相对密度。与Ti(C_0.7,N_0.3)基金属陶瓷相比，TiC基金属陶瓷在没有N元素的情况下具有较高的相对密度且无孔隙，但其晶粒较粗大。为了获得细晶粒和高密度的显微组织，将0.25%Cr₃C₂-0.75%VC（质量分数）引入到TiC基金属陶瓷中，获得了优异的硬度、横向断裂强度和韧性。另外，在Ti(C_0.7,N_0.3)基金属陶瓷中也添加了0.25%Cr₃C₂-0.75%VC，但其力学性能低于Ti(C_0.7,N_0.3)的金属陶瓷，这是因为细颗粒和反应颗粒与Ti(C,N)发生了急性固溶反应。研究了基于不同C/N比的Ti(C_x,N_1-x)基金属陶瓷的切削性能和摩擦性能。结果表明，具有0.25%Cr₂C₃-0.75%VC的TiC基金属陶瓷在室温下的摩擦系数最低，为0.15，在1000 r/min的高速切削过程中，使用寿命最长。     

Efficient first-order resonant near-infrared quantum cutting in β-NaYF4:Ho,Yb

We demonstrated an efficient two-photon near-infrared (NIR) quantum cutting (QC) in Ho³⁺-Yb³⁺ co-doped hexagonal β-NaYF₄, which could efficiently convert an incident high-energy photon in the wavelength region of 300-550 nm into two NIR photons. Underlying mechanism for the two-photon NIR-QC process is analyzed in terms of static and dynamic photoemission and monitored excitation spectra. It is found that NIR-QC can occur through two possible energy transfer (ET) approaches: (i) the excited Ho³⁺:⁵F₃ state may simultaneously excite two Yb³⁺ neighbors via a cooperative ET process, and (ii) the NIR-QC can be feasibly induced by a first Ho³⁺(⁵S₂,⁵F₄) + Yb³⁺(²F_7/2) → Ho³⁺(⁵I₆) + Yb³⁺(²F_5/2) resonant ET process and a sequential ⁵I₆ → ⁵I₈ transition of Ho³⁺. This novel NaYF₄:Ho³⁺,Yb³⁺ NIR-QC phosphor, may explore a new approach to maximize the performance of solar cells.     

CO2 laser cut quality of 4130 steel

Samples of 4130 steel were cut on a CO₂ laser cutting system and the combined effects of power and feed rate on kerf width, surface roughness, striation frequency and the size of heat affected zone (HAZ) have been studied. Regression analysis was used to develop models that describe the effect of the independent process parameters on laser cut quality. For the range of operation conditions tested, it was observed that power had a major effect on kerf width and size of HAZ, while feed rate affects were secondary. On the other hand, surface roughness and striation frequency were affected most by feed rate. At low power levels, the smallest kerf width and HAZ are obtained and the effect of feed rate is moderate. Low feed rates gave good surface roughness and low striation frequency. For optimum cut quality, kerf width, HAZ and surface roughness are kept at a minimum. However, operating conditions that satisfy these requirements while maintaining high productivity could not be identified.     

适于镀锌钢板激光焊接的CO2激光切割

研究适合于裁焊板生产的板坯切割的技术方案，重点讨论了CO2激光切割。采用氮气辅助激光切割，氧气辅助激光切割，铣切和普通剪切方法进行了镀锌钢板的切割。研究表明，氮气辅助CO激光切割方正度较好，切口质量符合裁焊板拼接间隙小于0．1mm的要求。激光切割时，由于热影响范围小，镀锌钢板切口边缘镀锌层烧损范围小，整个切缝无宏观残余形变。氮气辅助CO2激光切割具有切割速度快，质量好的优点，适合于进行裁焊板的板坯切割。     

Primary losses in disk and CO2 laser beam inert gas fusion cutting

Cutting experiments with CO₂ and disk lasers were carried out using a design of experiments (DOE) approach. The experimental evaluation of primary energy losses through the cut kerf and their dependence on the type of the applied laser source was performed. The primary energy losses consisting of directly transmitted and reflected laser power were gathered by collecting them within polymethylmethacrylate (PMMA) blocks placed under the sheets being cut. Cutting trials were performed on cold work steel test specimens with different sheet thicknesses. The particular feature of the applied experimental setup was the similar geometry of both the CO₂ and the disk laser beam with comparable values of the focus diameter and the Rayleigh length. Experimental results revealed lower values of primary energy losses in case of disk laser cutting if both processes are compared at the same values of relative cutting speed.     

Self-lubrication of sintered ceramic tools with CaF2 additions in dry cutting

An Al₂O₃/TiC ceramic cutting tool with the additions of CaF₂ solid lubricant was produced by hot pressing. The fundamental properties of this ceramic cutting tool were examined. Dry machining tests were carried out on hardened steel and cast iron. The tool wear, the cutting forces, and the friction coefficient between the tool–chip interface were measured. It was shown that the friction coefficient at the tool–chip interface in dry cutting of hardened steel and cast iron with Al₂O₃/TiC/CaF₂ ceramic tool was reduced compared with that of Al₂O₃/TiC tool without CaF₂ solid lubricant. The mechanisms responsible were determined to be the formation of a self-lubricating film on the tool–chip interface, and the composition of this self-lubricating film was found to be mainly CaF₂ solid lubricant, which was released and smeared on the wear track of the tool rake face, and acted as lubricating additive between the tool–chip sliding couple during machining processes. The appearance of this self-lubricating film contributed to the decrease of the friction coefficient. Cutting speed was found to have a profound effect on this self-lubricating behavior.     

Wear characteristics of TiC, Ti(C,N), TiN and Al2O3 coatings in the turning of conventional and Ca-treated steels

The wear characteristics of single layers of TiC, Ti(C,N), TiN and Al₂O₃ were investigated during turning of conventional and Ca-treated quenched and tempered Al-killed steels. The experimental coatings were deposited using chemical vapour deposition (CVD) or moderate temperature CVD (MTCVD) on cemented carbide substrates of a single composition and the coatings were of similar thicknesses (7 ± 1 μm). The wear mechanisms and layer formation were studied using scanning electron microscopy, optical microscopy and X-ray diffraction. Inclusion modification appeared to be an effective means of enhancing machinability and all experimental coatings exhibited about 20% better performance as a result of Ca-treatment. In particular, the crater wear of the experimental coatings — excluding Al₂O₃ — was clearly reduced. Comparative cutting tests revealed important differences between the coating materials. Wear mechanisms of the experimental coatings are discussed in detail.     

X-ray diffraction study of Ba0.985Na0.015Ti0.985Nb0.015O3, Ba0.6Na0.4Ti0.6Nb0.4O3 and Ba0.3Na0.7Ti0.3Nb0.7O3 compositions

The Ba_0.985Na_0.015Ti_0.985Nb_0.015O₃, Ba_0.6Na_0.4Ti_0.6Nb_0.4O₃ and Ba_0.3Na_0.7Ti_0.3Nb_0.7O₃ compositions of the (1 − x) BaTiO₃–xNaNbO₃ (BTNNx) system have been studied by X-ray diffraction and by measurements of dielectric properties. The specimens with composition BTNN (x = 0.015, 0.40 and 0.70) have been refined by the JANA program from X-ray powder diffraction data. Ceramic samples with composition (1 − x) BaTiO₃ + xNaNbO₃ (where x = 0.015, 0.40 and 0.70) were prepared by calcinations from appropriate mixture of BaCO₃, TiO₂, Na₂CO₃ and Nb₂O₅. The calcined powder was sintered at temperature range 1200–1400 °C. As the composition x increased from 0.015 (and 0.70), the ferroelectric ceramics (x = 0.015, FE) with tetragonal phase changed to the ferroelectric relaxors (RFE, x = 0.40). RFE ceramics showed a peculiar diffuse phase transition and dielectric relaxation at the low temperature (down to 180 K) due to a frustration between RFE and FE state. These ceramics present the classical ferroelectric character when 0 ≤ x < 0.075 and 0.55 < x ≤ 1 and relaxor character when 0.075 ≤ x ≤ 0.55.