Laser repairing surface crack of Ni-based superalloy components

Surface crack of components of the cast nickel base superalloy was repaired with twin laser beams under proper technological conditions. One laser beam was used to melt the substrate material of crack, and the other to fill in powder material to the crack region. The experimental results show that the surface crack with the width of 0.1 ～ 0.3?mm could be repaired under the laser power of 3?kW and the scanning speed of 6 ～ 8?mm/s. The repaired deepness of crack region is below 6.5?mm. The microstructure of repaired region is the cellular crystal, columnar crystal dendrite crystal from the transition region to the top filled layer. The phases in repaired region mainly consisted of supersaturated α Co with plenty of Ni, some Cr and Al, Cr 23 C 6, Co 2B, Co Ni Mo, Ni 4B 3, TiSi and VSi. The hardness of filled layer in repaired region ranged from HV 0.2 450 to HV 0.2 500, and the hardness decreases gradually from the filled layer to joined zone.

Combined studies of surface evolution and crack healing for the suppression of negative factors during CO_(2) laser repairing of fused silica

In order to reveal the evolution mechanism of repaired morphology and the material's migration mechanism on the crack surface in the process of CO_(2) laser repairing surface damage of fused silica optics, two multi-physics coupling mathematical models with different scales are developed, respectively. The physical problems, such as heat and mass transfer,material phase transition, melt flow, evaporation removal, and crack healing, are analyzed. Studies show that material ablation and the gasification recoil pressure accompanying the material splash are the leading factors in forming the Gaussian crater with a raised rim feature. The use of low-power lasers for a long time can fully melt the material around the crack before healing, which can greatly reduce the size of the residual air layer. Combined with the experimental research, the methods to suppress the negative factors(e.g., raised rim, deposited debris, air bubbles) in the CO_(2) laser repairing process are proposed.

Introduction of a New Method for Regulating Laves Phases in Inconel 718 Superalloy during a Laser-Repairing Process

The morphology,size,and distribution of Laves phases have important influences on the mechanical properties of laser-repaired Inconel 718(IN718)superalloy.Due to the deterioration of the substrate zone,the Laves phase in the laser cladding zone of IN718 superalloy cannot be optimized by a hightemperature solution treatment.In this study,an in situ laser heat-treatment method was proposed to regulate the morphology and size of the Laves phase in the laser cladding zone of IN718 superalloy without impacting the substrate zone.In the in situ laser heat-treatment process,a laser was used to heat previously deposited layers with optimized manufacturing parameters.A thermocouple and an infrared camera were used to analyze thermal cycles and real-time temperature fields,respectively.Microstructures and micro-segregations were observed by optical microscopy,scanning electron microscopy,and electron probe microanalysis.It was found that the in situ laser heat treatment effectively changed the morphology and size of the Laves phase,which was transformed from a continuous striplike shape to a discrete granular shape.The effective temperature range and duration were the two main factors influencing the Laves phase during the in situ laser heat-treatment process.The effective temperature range was determined by the laser linear energy density,and the peak temperature increased with the increase of the linear energy density.In addition,the temperature amplitude could be reduced by simultaneously increasing the laser power and the scanning velocity.Finally,a flow diagram was developed based on the in situ laser heat-treatment process,and the deposition of a single-walled sample with fine and granular Laves phases was detected.

Optical modulation of repaired damage site on fused silica produced by CO2 laser rapid ablation mitigation

CO2 laser rapid ablation mitigation(RAM)of fused silica has been used in high-power laser systems owing to its advantages of high efficiency,and ease of implementing batch and automated repairing.In order to study the effect of repaired morphology of RAM on laser modulation and to improve laser damage threshold of optics,an finite element method(FEM)mathematical model of 351 nm laser irradiating fused silica optics is developed based on Maxwell electromagnetic field equations,to explore the 3D near-field light intensity distribution inside optics with repaired site on its surface.The influences of the cone angle and the size of the repaired site on incident laser modulation are studied as well.The results have shown that for the repaired site with a cone angle of 73.3°,the light intensity distribution has obvious three-dimensional characteristics.The relative light intensity on z-section has a circularly distribution,and the radius of the annular intensification zone increases with the decrease of z.While the distribution of maximum relative light intensity on y-section is parabolical with the increase of y.As the cone angle of the repaired site decreases,the effect of the repaired surface on light modulation becomes stronger,leading to a weak resistance to laser damage.Moreover,the large size repaired site would also reduce the laser damage threshold.Therefore,a repaired site with a larger cone angle and smaller size is preferred in practical CO2 laser repairing of surface damage.This work will provide theoretical guidance for the design of repaired surface topography,as well as the improvement of RAM process.

Applications of lasers:A promising route toward low-cost fabrication of high-efficiency full-color micro-LED displays

Micro-light-emitting diodes(micro-LEDs)with outstanding performance are promising candidates for next-generation displays.To achieve the application of high-resolution displays such as meta-displays,virtual reality,and wearable electronics,the size of LEDs must be reduced to the micro-scale.Thus,traditional technology cannot meet the demand during the processing of micro-LEDs.Recently,lasers with short-duration pulses have attracted attention because of their unique advantages during micro-LED processing such as noncontact processing,adjustable energy and speed of the laser beam,no cutting force acting on the devices,high efficiency,and low cost.Herein,we review the techniques and principles of laser-based technologies for micro-LED displays,including chip dicing,geometry shaping,annealing,laserassisted bonding,laser lift-off,defect detection,laser repair,mass transfer,and optimization of quantum dot color conversion films.Moreover,the future prospects and challenges of laser-based techniques for micro-LED displays are discussed.

Microstructure and mechanical properties of laser additive repaired Ti17 titanium alloy

Laser additive manufacturing technology with powder feeding was employed to repair wrought Ti17titanium alloy with small surface defects.The microstructure,micro-hardness and room temperature tensile properties of laser additive repaired(LARed)specimen were investigated.The results show that,cellular substructures are observed in the laser deposited zone(LDZ),rather than the typicalαlaths morphology due to lack of enough subsequent thermal cycles.The cellular substructures lead to lower micro-hardness in the LDZ compared with the wrought substrate zone which consists of duplex microstructure.The tensile test results indicate that the tensile deformation process of the LARed specimen exhibits a characteristic of dramatic plastic strain heterogeneity and fracture in the laser repaired zone with a mixed dimple and cleavage mode.The tensile strength of the LARed specimen is slightly higher than that of the wrought specimen and the elongation of11.7%is lower.

Laser Repair of Steam Turbine Blades(Invited Paper)

Reliable and efficient power generation is a major global issue due to both political and environmental concerns.Nevertheless many critical components,particularly the blades of the low pressure(LP) side of power generating steam turbines,are subjected to failure due to severe erosion at the leading edges.Since taking machines off-line for maintenance and removal of damaged blade for repair is extremely expensive,increasing the service life of these critical components can offer significant economic and political benefits.Conventional techniques to increase service life include brazing of an erosion shield at the leading edge of the turbine blades,open arc hardfacing,and cladding with erosion resistant materials using gas tungsten,manual metal or plasma transferred arc welding.We have been investigating for the past eight years the potential of laser cladding to deposit a high quality and erosion resistant protection shield on the leading edge of LP blades.Laser cladding offers unique advantages over the conventional techniques.The project to-date has demonstrated the feasibility of in-situ repair of turbine blades in trials conducted at a power station using a fibre delivered Laserline diode laser and a robot.A company(Hardwear Pty.Ltd.) has been established to commercialise the technology and has delivered two commercial contracts.

Compatibility research of laser additive repairing TA15 forgings with Ti6Al4V-xTA15 alloy

The application of mixed powders with different mass fraction on laser additive repairing(LAR)can be an effective way to guarantee the performance and functionality of repaired part in time.A convenient and feasible approach is presented to repair TA15 forgings by employing Ti6Al4V-xTA15 mixed powders in this paper.The performance compatibility of Ti6Al4V-xTA15 powders from the aspects of microhardness,tensile property,heat capacity,thermal expansion coefficient and corrosion resistance with the TA15 forgings was fully investigated.The primaryαlaths were refined and the volume fraction of the secondaryαphase was increased by increasing the mass fraction of TA15 in the mixed Ti6Al4V-xTA15 powders,leading to varied performances.In conclusion,the mixed Ti6Al4V-70%TA15(x=70%)powders is the most suitable candidate and is recommended as the raw material for LAR of TA15 forgings based on overall consideration of the compatibility calculations of the laser repaired zone with the wrought substrate zone.

Numerical simulation of the modulation to incident laser by the repaired damage site in a fused silica subsurface

One of the main factors of laser induced damage is the modulation to incident laser which is caused by the defect in the subsurface of the fused silica. In this work, the repaired damage site irradiated by CO2 laser is simplified to a Gaussian rotation according to the corresponding experimental results. Then, the three-dimensional finite-difference time-domain method is employed to simulate the electric field intensity distribution in the vicinity of this kind of defect in fused silica front subsurface. The simulated results show that the modulation is notable, the Emax is about 2.6 times the irradiated electric field intensity in the fused silica with the damage site （the width is 1.5 μm and depth is 2.3 μm） though the damage site is repaired by CO2 laser. The phenomenon and the theoretical result of the annular laser enhancement existed on the rear surface are first verified effectively, which agrees well with the corresponding experimental results. The relations between the maximal electric field intensity in fused silica with defect depth and width are given respectively. Meanwhile, the corresponding physical mechanism is analysed theoretically in detail.

Laser therapy on points of acupuncture on nerve repair

Paresthesia is the name given to a temporary or permanent sensory loss caused by several surgical procedures that affected the peripheral sensory nerve.In dentistry,common iatrogenic procedures that can lead to sensory loss include third molar removal,

Roles of reinforced nerve conduits and low-level laser phototherapy for long gap peripheral nerve repair

Peripheral nerve injuries are common in clinical practice because of traumas such as crushing and sectioning. Lesions of the nerve structure result in lost or diminished sensitivity and/or motor activity in the innervated territory. The degree of lesion depends on the specific nerve involved, the magnitude and type of pres- sure exerted, and the duration of the compression. The results of such injuries commonly include axonal degeneration and retro- grade degeneration of the corresponding neurons in the spinal medulla, followed by very slow regeneration （Rochkind et al., 2001）. The adverse effects on the daily activities of patients with a peripheral nerve injury are a determining factor in establishing the goals of early recovery （Rodriguez et al., 2004）.

水下激光修复研究现状与发展趋势

海洋装备的维修养护与事故抢修技术既是人类进行远洋探索与资源开发的重要保障,又是核电站、水利工程等重要基础设施在役运维的有力技术支撑,而水下激光修复正是这一领域中极具前景的解决方案之一.激光修复技术作为陆地上常规环境中的优势技术,近年来也在水下环境中有了长足的发展,已在海洋油气资源的开采与运输、船舶应急维修、船坞港口装备、水利工程、核动力工程等领域得到了广泛的关注与研究.为了进一步总结并分析水下激光修复技术所面对的问题与现有解决方案,从水下激光修复技术的研究现状入手,综述了水下湿法、高压干法和局部干法激光修复技术的工艺问题及其产生机理,并分析对比了多种对应主流解决方案的改善效果与研究进展,最后对水下激光修复技术的发展趋势进行了总结与展望.

非(001)晶面促进激光单晶熔凝过程中柱状晶外延生长

当激光熔池内的柱状枝晶沿着熔池边界外延生长时,其方向并不严格平行于温度梯度,而是选择与基体一致的择优方向生长,因此基体取向可以影响柱状晶的外延生长行为。在使用激光金属成型/沉积技术修复昂贵的单晶部件时,需要考虑这一特性。现有研究已经实现了(001)晶面上的柱状晶完全外延生长进而获得完整单晶。然而由于叶片形状复杂,实际修复过程中可能会遇到的不同取向表面。论文对(001)和非(001)取向表面修复过程中的杂晶形成能力进行了比较研究,通过数值计算获得了控制微观组织的局部凝固变量,并将杂晶晶粒的体积分数作为量化单晶完整性指数。结果表明,与(001)晶面相比,多数非(001)晶面可以促进柱状晶的外延生长,进而获得更好的单晶完整性,实验结果也验证了这一结论。分析显示不同枝晶生长区域的边界是杂晶形成敏感区,两种晶面的差异在于边界数目及其位置。研究结果可以优化修复和制造应用中的沉积方向和激光加工窗口提供指导。

海藻糖敷料对激光损伤兔皮肤屏障功能的修复及体外促细胞生长、迁移和抗炎作用研究

目的:探究海藻糖敷料对激光损伤兔动物模型皮肤的修复作用,并探索其体外促细胞生长、迁移和抗炎作用。方法:试验兔脊柱两边各脱毛4个区域,随机分为正常组(N)、模型组(M)、对照组(P)和实验组(T)。除正常组外,其余各组使用激光照射造模;对照组及实验组分别使用透明质酸敷料及海藻糖敷料贴敷。于第0天、第3天、第7天、第14天和第21天对创面进行红斑和焦痂、水肿程度评分,以评价海藻糖敷料对皮肤修复效果。以L929细胞及HaCaT细胞为研究对象探索海藻糖敷料体外促细胞生长、迁移和抗炎作用。将细胞分为空白组(培养基)、正常组(细胞液+培养基)、对照组(细胞液+培养基+透明质酸)及实验组(细胞液+培养基+海藻糖)。使用MTT比色法检测各组L929细胞24 h、48 h及72 h增殖率,划痕试验检测各组L929细胞6 h、12 h和24 h迁移力;使用TNF-α及IFN-γ诱导HaCaT细胞建立炎症反应模型后,24 h后检测各组IL-6、IL-8和MDC表达水平。结果:创面给予敷料后7 d,实验组水肿评分[(1.1±0.3)分]较模型组[(1.2±0.4)分]显著降低(P<0.05);第14天,相较于模型组,实验组及对照组水肿、红斑焦痂评分有下降趋势但差异无统计学意义(P>0.05)。病理结果显示,对照组、实验组较模型组第14天炎细胞浸润微有减少。细胞实验结果显示,与正常组相比,对照组和实验组4 h、48 h及72 h的细胞增殖率均有明显增加;与正常组相比,对照组及实验组6 h、12 h和24 h的细胞迁移率均有明显增加(P<0.05);与细胞炎症模型组相比,实验组细胞上清液中IL-6、IL-8和MDC的表达水平明显降低(P<0.01)。结论:海藻糖敷料对激光所致兔皮肤屏障受损创面的组织炎症、愈合有一定修复作用;其机制可能与其能促进细胞增殖、细胞迁移及抑制炎症的功能相关。

重组贻贝粘蛋白在点阵CO_(2)激光治疗面部痤疮萎缩性瘢痕术后创面修复中的应用研究

目的:探究重组贻贝粘蛋白水凝胶敷料(Recombined mussel adhesive protein hydrogel dressing,Rmaphd)在点阵CO_(2)激光治疗面部痤疮萎缩性瘢痕术后创面修复中的应用效果。方法:选择2022年6月-2023年2月面部痤疮萎缩性瘢痕患者117例,分为Rmaphd组、重组人表皮生长因子(Recombinant human epidermal growth factor,rhEGF)组和对照组,每组39例,三组均给予点阵CO_(2)激光术治疗,术后分别给予Rmaphd、rhEGF及生理盐水处理,比较三组疗效、ECCA评分、症状持续时间以及生活质量评分。结果:Rmaphd组和rhEGF组总有效率分别为92.31%和94.87%,均高于对照组76.92%(P<0.05),术后ECCA评分低于对照组(P<0.05),术后疼痛、红斑、痂皮持续时间短于对照组(P<0.05),Acne-QoL各指标得分优于对照组(P<0.05);上述各临床Rmaphd组与rhEGF组差异无统计学意义(P>0.05)。结论:Rmaphd用于点阵CO_(2)激光治疗面部痤疮萎缩性瘢痕术后创面修复疗效显著,具备在临床上辅助激光治疗术后修复的应用潜力。

30Cr13钢叶轮轴激光熔覆修复材料与修复工艺

针对受损30Cr13钢叶轮轴的修复问题,对30Cr13钢叶轮轴开展不同修复材料下的激光熔覆修复可行性研究。测量母材腐蚀磨损情况,选择修复材料,形成修复工艺,并对修复效果进行校核。结果表明,修复后的叶轮轴各项主要性能均满足技术指标要求。采用激光熔覆技术可有效延长30Cr13钢叶轮轴的使用寿命,降低生产成本。

激光定向能量沉积Al-Mg-Sc-Zr修复5083-H112铝合金的组织和性能

激光定向能量沉积增材修复技术具有时间短、效率高、成本低、力学性能好等优点,具有很大的发展潜力。采用Al-7.5Mg-0.3Sc-0.28Zr作为修复材料对轨道交通用5083-H112铝合金进行激光修复实验,得到了致密、无缺陷的修复试样,并对其组织和性能进行研究,探讨了激光修复铝合金的可行性。结果表明,熔合线附近过渡区可划分为修复区、部分熔化区、热影响区和母材。修复区为完全等轴晶,由平均晶粒尺寸为4.95μm的细晶带和18.34μm的粗晶区组成。从修复区到部分熔化区再到热影响区的过渡区域,Al元素含量逐渐升高,Mg元素含量逐渐下降,硬度逐渐下降,修复后母材未被软化。由于激光增材制造技术的快速凝固,在熔合线附近的细晶带有较大的应力集中,由于较小的热输入在部分熔化区、热影响区的残余应力较小。修复试样的屈服强度为(152±2)MPa,为母材的89.4%;抗拉强度为(305±5)MPa,为母材抗拉强度的100%;伸长率为(15.5±0.5)%,为母材的85.2%;断裂发生在强度较弱的母材。高性能的激光修复铝合金是可实现的,具有广泛的应用前景。

采用增减材复合制造技术的模具修复工艺研究

激光金属沉积增减材复合制造技术是实现模具等高附加值部件修复与再制造的理想候选工艺之一。为了提高模具修复的效率和精度,本文将增减材复合制造技术应用于模具修复领域,并且对修复工艺进行研究。首先根据具体使用工况和材料性能要求,确定了最佳模具修复参数,随后讨论了该模具修复工艺的应用条件和应用范围。实验结果表明:利用本文提出工艺方案进行模具修复时可以实现修复区域无拼接痕迹,并且修复区域硬度提升7.4 HRC,能够有效提升模具的使用性能。

湿润烧伤膏在儿童大面积鲜红斑痣激光治疗创面修复中的应用

目的观察湿润烧伤膏联合脉冲染料激光对提升儿童大面积鲜红斑痣整体治疗效果的影响,以期指导临床相关疾病治疗。方法本文为随机对照试验,研究对象选自2022年1月至2022年9月湖南省人民医院收治60例大面积鲜红斑痣患儿,采用随机数字表法将其分为两组,各30例。对照组男童12例,女童18例,年龄(6.25±1.02)岁;试验组男童10例,女童20例,年龄(6.35±1.05)岁。对照组采取595 nm脉冲染料激光治疗联合常规抗炎软膏护理创面,试验组采取595 nm脉冲染料激光联合湿润烧伤膏护理创面。对比两组治疗效果、红痣瘢痕消退程度[采用温哥华瘢痕量表(VSS)评估]、疼痛程度(采用国际数字疼痛分级标准评估)、不良反应。采用t检验、χ^(2)检验、秩和检验。结果试验组治疗总有效率高于对照组[96.67%(29/30)比70.00%(21/30)],差异有统计学意义(χ^(2)=7.680,P<0.05)。治疗结束时,试验组红痣瘢痕消退程度(VSS评分)低于对照组[(1.25±0.85)分比(4.02±1.12)分],差异有统计学意义(t=10.791,P<0.05);治疗结束时,试验组疼痛程度低于对照组[(1.02±0.25)比(3.02±0.52)],差异有统计学意义(t=18.986,P<0.05)。试验组不良反应总发生率低于对照组[10.00%(3/30)比43.33%(13/30)],差异有统计学意义(χ^(2)=8.523,P<0.05)。结论595 nm脉冲染料激光联合湿润烧伤膏可显著提高儿童大面积鲜红斑痣的治疗效果,利于红痣瘢痕消退,改善疼痛程度,提升患儿治疗过程中的舒适度,且安全可靠。

超声振动对激光修复镍基高温合金晶粒特征及其缺陷的影响

目的研究超声振动对激光修复镍基高温合金梯形槽修复区显微组织及力学性能的影响,为实现高温合金的高质量激光增材修复提供参考。方法以镍基高温合金为基体和修复材料,并将超声振动引入激光增材修复过程中。采用光学显微镜,对比分析有无超声振动时梯形槽修复区的显微组织结构;采用电子背散射衍射(EBSD)、扫描电镜(SEM)、能谱仪(EDS)等设备,表征不同超声功率下梯形槽修复区的晶粒取向、析出相分布和元素组成;结合试验研究与机理分析,揭示超声振动对修复区晶粒特征和缺陷的影响规律。结果超声振动减少了梯形槽修复区底角的缺陷,修复区一次枝晶间距平均值由6.74μm减至3.38μm,晶粒平均尺寸由58.4μm降至50.2μm,等轴晶占比由46.6%增至63.4%,Laves相析出含量减少。当超声功率为4000 W时,梯形槽修复区的平均显微硬度为256.2HV0.2,相较于无超声振动时提高了17.7HV0.2。结论在超声振动作用下,梯形槽底角的熔合不良缺陷得到抑制,一次枝晶间距减小,长条状Laves相转变为颗粒状Laves相,且随着超声功率的增大,梯形槽修复区的平均显微硬度逐渐增大。