氧化锆热障涂层在液芯大压下轧机轧辊上的应用

利用有限元软件ABAQUS对热力耦合作用下热障涂层对液芯轧机轧辊应力场、温度场的影响进行分析;采用等离子喷涂方法在轧辊材料H13钢表面制备厚度0.5mm的氧化锆热障涂层,并对其进行激光重熔处理,研究等离子喷涂热障涂层和激光重熔涂层的硬度、抗热冲击性能。结果表明,热障涂层能有效降低轧辊表面温度和等效应力,缓解热冲击效应,延长轧辊使用寿命;相对于等离子喷涂涂层,激光重熔涂层具有更大的硬度和更好的抗热冲击性能,在提高轧辊使用寿命方面有着更好的前景。     

TiO2涂层激光热冲击损伤机理研究

研究了等离子喷涂TiO2涂层在激光热冲击条件下激光输出功率对涂层损伤的影响，并探讨了涂层的损伤机理。结果表明，随着激光输出功率的增大，TiO2涂层损伤加剧，当激光输出功率为3900W时被击穿：基体上产生热影响区；TiO2涂层在激光热冲击下的微观损伤形貌主要以放射板条状组织和枝状组织为主，并存在大量的裂纹；TiO2涂层消耗激光能量的方式主要是熔化与再结晶并辅以裂纹的萌生与扩展。     

气焊及切割工艺与设备

水下自动套料切割定位系统,等离子弧切割装置的改进[英],径向基神经网络在三维激光切割中的应用，激光冲击加工表面涂层厚度的优选,CO2激光用于船体型线放样切割的研究及应用,[编者按]     

TC4钛合金表面激光冲击强化-微弧氧化涂层的组织和性能

通过激光冲击强化(LSP)在TC4钛合金表面制备细晶粒过渡层，再采用微弧氧化(MAO)制备LSP-MAO复合涂层，研究TC4钛合金表面MAO涂层及LSP-MAO复合涂层的显微组织、相结构、显微硬度和耐磨性。结果表明：激光冲击强化处理后，TC4钛合金衍射峰变宽，表层晶粒明显细化。与MAO涂层相比，LSP-MAO复合涂层表面的孔径更小，表面更加平整，显微硬度和强化层深度有所增加，其中激光冲击2次时显微硬度最高，达到636.3 HV0.025(距离表面30μm处),其强化层最大深度达到390μm。LSP-MAO涂层的耐磨性均优于MAO涂层，其中激光冲击强化2次时LSP-MAO复合涂层耐磨性最好。     

激光重熔纳米氧化锆热障涂层的抗热冲击性能

采用纳米氧化锆团聚粉末和等离子喷涂技术制备了纳米氧化锆涂层,试验研究了激光重熔工艺参数(激光比能量)对纳米氧化锆涂层抗热冲击性能的影响.结果表明,激光重熔工艺参数对重熔涂层的抗热冲击性能影响显著,采用合适的工艺参数(激光比能量),可以使重熔涂层获得最佳的抗热冲击性能.不同激光重熔工艺参数处理的涂层形成的组织结构不同,使得涂层的抗热冲击性能不同.合适的激光重熔工艺参数下涂层表现出高的抗热冲击性能,主要是因为重熔后的涂层组织结构有利于热应力的释放以及其相结构在高温冲击下具有良好的稳定性.     

激光冲击处理对304不锈钢力学性能的影响

选用不同涂层对304不锈钢板材激光冲击处理,研究了自主研制的硅酸乙脂涂层与几种常用吸收涂层对304不锈钢的硬度和表面残余应力等冲击力学性能的影响.结果表明,在激光冲击过程中,黑漆涂层、铝箔涂层和硅酸乙脂黑漆涂层都能有效提高激光冲击试样的表面硬度,激光连续冲击后,在304不锈钢试件表面能形成1mm厚的硬化层,其表面硬度最大到240HV;随着激光功率密度的增强,其表面硬度逐渐增强;其表面残余应力也随着激光功率密度的增加而逐渐增大.     

无涂层激光冲击强化对40CrNiMo结构钢摩擦磨损性能的影响

目的 采用无涂层激光冲击强化技术诱导残余压应力和细化晶粒,提高40CrNiMo结构钢的显微硬度及耐磨性。方法 采用高功率激光束对40CrNiMo结构钢表面进行激光冲击强化处理,通过显微组织观察、XRD检测、显微硬度测试、残余应力测试、摩擦磨损实验及磨损形貌观察,对比分析未处理试样、有涂层激光冲击强化处理试样和无涂层激光冲击强化处理试样的显微组织、显微硬度、残余应力和摩擦磨损性能。结果 在有/无铝箔涂层、去离子水约束层作用下分别对40CrNiMo结构钢试样进行有涂层/无涂层激光冲击强化处理,诱导产生残余压应力和晶粒细化,试样表面显微硬度分别提高至313.5HV和336.9HV,提高了约13.5%和21.9%,表面最大残余压应力达到–405.3 MPa和–326.6 MPa;有涂层激光冲击强化处理试样的摩擦因数较稳定,降低了约14.1%,而无涂层激光冲击强化处理试样的摩擦因数出现较大波动,在摩擦磨损前期,摩擦因数降低了22.9%;在摩擦磨损中后期,摩擦因数降低了7.9%。未处理试样的磨损量为13 mg,有涂层激光冲击强化处理试样和无涂层激光冲击强化处理试样的磨损量分别为6mg和8mg,减少...     

TiO2涂层激光热冲击损伤机理研究

研究了等离子喷涂TiO2涂层在激光热冲击条件下激光输出功率对涂层损伤的影响,并探讨了涂层的损伤机理.结果表明,随着激光输出功率的增大,TiO2涂层损伤加剧,当激光输出功率为3900W时被击穿;基体上产生热影响区;TiO2涂层在激光热冲击下的微观损伤形貌主要以放射板条状组织和枝状组织为主,并存在大量的裂纹;TiO2涂层消耗激光能量的方式主要是熔化与再结晶并辅以裂纹的萌生与扩展.     

恒定动能Si3N4颗粒重复冲击不同厚度TiN/Ti涂层损伤特征对比分析

目的 研究砂粒冲击航空发动机压气机叶片不同厚度的TiN/Ti硬质涂层损伤特征与机理。方法 采用Si3N4硬质球恒定动能垂直重复冲击试验方法,研究厚度对TiN/Ti涂层冲击损伤的影响。通过对比涂层动力学响应、能量吸收率、冲击坑点轮廓、H3/E2值和损伤形貌,分析不同厚度涂层的冲击坑点损伤特征。利用ABAQUS软件仿真获得垂直冲击下涂层的应力分布。结果 在调制比为9∶1的两层TiN/Ti涂层中,厚度为25 μm的涂层坑点直径最大,达到382.49 μm,比坑点直径最小的涂层（20 μm）大了24.8%;厚度为25 μm的涂层坑点最深,达到8.17 μm,比坑点最浅的涂层（15 μm）大了49.9%;厚度为5 μm涂层的接触力峰值最大,为161.4 N,比接触力峰值最小的涂层（20 μm）大了26.1%。随着涂层厚度的增加,涂层的抗冲击能力先增加后减小,厚度为20 μm的涂层抗冲击能力最好。冲击坑点损伤特征有三种：中心区与过渡区的疲劳剥落与疲劳磨损,边缘区的疲劳圆周裂纹与疲劳剥落,涂层/基体变形,其中,以剥落为主。结论 硬质层内的应力梯度和重复交变拉/压应力导致硬质层内产生疲劳圆周裂纹和疲劳剥落,硬质层与结合层界面处的高应力梯度导致产生层间疲劳剥落。     

镍基熔覆层表面超声冲击处理组织及耐蚀性研究

目的 提升激光熔覆Ni基涂层表面组织及耐蚀性能。方法 采用激光熔覆技术制备成形好、无裂纹的Ni基涂层，随后进行超声冲击处理。采用扫描电子显微镜（SEM）、电子探针（EPMA）及电化学设备等，研究熔覆层和冲击硬化层的组织及耐蚀性能，分析Ni基熔覆层的冲击强化机制。结果 激光熔覆Ni基涂层主要由γ-(Fe,Ni)固溶体和晶界碳化物组成，组织形貌由底及表为胞状树枝晶和细小的树枝晶。熔覆层内晶界的Cr元素含量高于晶内，且上部枝晶内的Cr元素含量高于底部和中部。超声冲击处理未改变熔覆层内的物相组成，但在表面形成厚度约5 μm的细晶层，冲击硬化层内晶界的碳化物被破碎成细小的碳化物并弥散分布于晶内，起到细晶强化和弥散强化的作用。超声冲击后，表面粗糙度由0.52 μm降至0.29 μm，硬度提升50%以上。电化学测试表明，冲击硬化层的平均自腐蚀电位上升37.21 mV，平均自腐蚀电流密度下降57.9%，腐蚀表面均匀平整，大量细小的碳化物弥散分布。结论 超声冲击处理细化了Ni基熔覆层的表层组织，且表面的耐蚀性能明显提高。     

渗铝激光冲击复合处理对00Cr12合金钢高温拉伸性能的影响

利用大功率Nd:YAG激光对渗铝后的00Cr12合金钢进行了冲击强化处理,并在不同温度下对其进行了高温拉伸试验,从力学性能及断口形貌等分析了渗铝复合激光冲击对其高温拉伸性能的影响。结果表明,00Cr12合金钢渗铝后表面形成的铝化物涂层在高温拉伸过程中具有较高的热稳定性及抗氧化性能,表现出优异的热疲劳性能,而且激光冲击处理可以使渗铝层组织更加致密并且与基体结合更加紧密。     

激光冲击处理对焊接接头力学性能的影响(Ⅰ)

当短脉冲、高峰值功率密度 (>10 13 W /m2 )的激光辐射金属靶材时 ,就产生高温、高压等离子体 ,该等离子体受到约束层的约束时产生高强度应力波冲击金属表面并向内部传播 ,在材料表面产生应变硬化 ,称这种表面强化技术为激光冲击处理或激光喷丸。激光冲击处理可以提高材料表层硬度、强度 ,并获得比传统的喷丸技术更深的硬化层或残余压应力层 ,从而更有利于材料疲劳性能的提高 ,为研究激光冲击处理在焊后强化方面的应用 ,本文对 1.6 6mm厚的镍基高温合金GH30、1.2mm厚的奥氏体不锈钢1Cr18Ni9Ti板材焊缝进行了激光冲击处理 ,对比了激光冲击处理试件和未经激光冲击处理试件焊逢的表层显微硬度、残余应力、抗拉强度和疲劳寿命 ,发现激光冲击处理能提高GH30氩弧焊焊接接头抗拉强度 12 % ,提高 1Cr18Ni9Ti等离子焊接接头疲劳寿命30 0 %以上。     

Laser surface modification of AISI 410 stainless steel with brass for enhanced thermal properties

Brass coating was applied to AISI410 steel using high power laser in a laser engineered net shaping (LENS™) system. The influence of laser treatment on interfacial microstructure and thermal performance was evaluated as a function of coating thickness. Laser deposition resulted in a diffused and metallurgically sound interface between metallurgically incompatible brass coating and AISI410 steel substrate. The thermal conductivity of AISI410 steel increased from 27 W/mK to a maximum of 37 W/mK depending on the coating thickness, almost 50% gain. The absence of sharp interface between the coating and the substrate, as a result of laser processing, resulted in a low interfacial thermal contact resistance. Thermal performance tests showed that the brass coating can enhance the heat transfer rate of stainless steel substrate. These results show that novel and efficient feature based coatings can be exploited using laser-based advanced manufacturing technologies for various industrial applications.     

纳米ZrO2激光重熔涂层组织与性能分析

采用金相试验、扫描电镜试验、热震试验和显微硬度试验对不同激光重熔工艺下的Y2O3部分稳定ZrO2纳米陶瓷涂层组织与性能进行研究.重点分析了涂层重熔宽度与深度、表面形貌、显微硬度和热震性能随激光比能量的变化规律.结果表明,ZrO2纳米陶瓷涂层的重熔深度和宽度随着激光比能量的增大而增加;涂层的表面成形与激光比能量密切相关;涂层的显微硬度随激光比能量的增大而升高;激光比能量对涂层热震性能的影响十分明显,当激光比能量为37.2 J/mm2时重熔涂层的热震性能最好.     

工艺参数对送粉激光熔覆层几何形貌的影响

系统地研究了Ｎｉ基合金自动送粉激光熔覆工艺参数对熔覆层几何形貌的影响。重点讨论了一一些参数和如激光作用能量密度、作用时间、送粉速率、扫描速度等对熔覆层宏观质量的影响规律。利用金相法检测了熔履层的几何参数。为解释工艺参数对熔覆层宏观质量的影响提出了送粉不各种各样科班经的概念,并利用检测的熔覆层宏观参数计算了覆盖率。覆盖率随扫描速度增加而减小,随送粉速率的增加而增。在本试验条件下,研究结果表明,随激光     

Laser surface modification using Inconel 617 machining swarf as coating material

A single-stage, blown powder laser cladding process is used to deposit a protective layer of Ni-based alloy Inconel 617 on mild steel substrates. A Design of Experiments methodology is used to analyse the effects of the major laser cladding processing parameters on the deposited layer characteristics. Layer thickness, microstructure, dilution, elemental composition and corrosion resistance are analysed and correlated with the processing parameters and the overall effectiveness of the protective coating assessed. The work is different in that the protective material, usually in the form of costly powder, is in this case virtually cost-free and simply recycled from machining waste without any costly atomisation or similar process. The results show a number of significant relationships between the processing parameters and the effectiveness of the protective coating. The layer thickness and hardness were found to increase with the mass feed rate and decrease with an increase in laser power. A mainly columnar dendritic microstructure was observed in the clads. There was no evidence of significant bonding defects, trapped unmelted particles or porosity under most conditions. In all samples, the coatings displayed significant higher corrosion resistance than the mild steel sample.     

An investigation on selective laser melting of Al-Cu-Fe-Cr quasicrystal: From single layer to multilayers

In this study, the effects of processing parameters on the microstructure of Al-Cu-Fe-Cr quasicrystalline (QC) coatings fabricated by selective laser melting (SLM) are investigated. A qualitative analysis on the XRD patterns indicates that the phase composition for the SLM processed coating mainly consisted of Al-Cu-Fe-Cr quasicrystals and α-Al (CuFeCr) solid solution, and with increasing laser energy input or coating thickness, the volume fraction of QC i-Al₉₁Fe₄Cr₅ reduced and those of QC d-Al₆₅Cu₂₀Fe₁₀Cr₅ and crystalline θ-Al₂Cu increased. The formation of cracks during the coating building procedure from single layer to multilayers is also discussed. For the coatings with the same layer number, the pores and balling particles diminish as laser power increases, due to the growth of melting degree. At the early stage of fabrication, with increment of layer number (or coating thickness), pores and balling particles decrease considerably because the molten pool solidified more “slowly”. However, after the layer number increases continuously from 10 to 20, the porosity no longer decreases, and some big size pores, microcracks and fractures appear, especially for the sample obtained at lower laser power. A wavy-like pattern composed chiefly of Al and QC phases, is formed at the interfacial region between substrate and coating due to Marangoni effect.     

Introduction of compressive residual stresses in Ti-6Al-4V simulated airfoils via laser shock processing

Ti-6Al-4V (Ti-64) simulated airfoils were laser shock processed with two laser power densities (4 and 9 GW/²) for each of three pulse repetition treatments (1, 3, and 5 shocks/spot). The microstructural effects of laser shock processing (LSP) on the Ti-64 were studied via scanning electron microscopy (SEM). Ultrasonic nondestructive inspection (NDI) was conducted to ensure that the LSP treatments resulted in no internal damage to the simulated airfoils. In-depth residual stress and cold work measurements were made using x-ray diffraction. No substantial changes due to LSP were found in the microstructure, and no internal damage was detected during NDI or metallographic sectioning. It was found that the in-depth residual stress and cold work states induced by LSP were a function of laser power density and pulse repetition. It was possible to induce compressive residual stresses in the direction most critical for the prevention of fatigue-crack growth throughout the thickness of the simulated airfoil leading edge.     

激光参数对Ti6Al4V钛合金激光冲击成形的影响

研究在Ti6Al4V合金激光冲击成形过程中,不同激光参数对板料弯曲角及表层硬度的影响。结果表明:当激光功率密度小于3GW/cm2时,弯曲角随着激光功率密度线性增加,激光功率密度超过3GW/cm2时,由于表面熔化现象的出现,弯曲角出现减小的趋势;板料弯曲角随冲击次数的增加也呈线性增长,但弯曲阻力的增加使得弯曲角的增长速度逐渐减慢;随着激光功率密度的增加,材料表面冲击区的硬度增高,表面硬化层的显微硬度最高达HV490,硬化层厚度约为1.0mm。