高压涡轮导向叶片气膜孔皮秒激光加工试验

针对高压涡轮导向叶片气膜孔加工问题,进行了皮秒激光加工DD5高压涡轮导向叶片的试验,采用正交试验法研究了激光功率、离焦量及单层进给量对叶片气膜孔加工的重熔层、锥度和加工效率的影响规律。结果表明：气膜孔的加工效率随着激光功率和单层进给量的增加呈上升趋势,孔由正锥形变为圆孔或微倒锥后再变为正锥形;皮秒激光处于负离焦状态时,气膜孔的重熔层更易控制,且孔更易接近圆孔或倒锥形;当加工参数为激光功率60 W、离焦量-0.2 mm、单层进给量0.03 mm时,加工的气膜孔呈现直圆孔,无重熔层、热影响区和微裂纹。     

电火花打孔对单晶高温合金损伤的多角度表征方法及损伤机理

本文旨在研究多种工艺参数下电火花打孔对新一代单晶高温合金的损伤行为,通过进行加工电流、脉冲宽度与脉冲间隔3种参数变化的25组正交试验,采用激光共聚焦显微镜、扫描电子显微镜（SEM）、能谱仪（EDS）、电子背散射仪（EBSD）等表征手段对打孔形成的不同损伤的影响规律进行研究。结果表明:加工电流对孔壁粗糙度和重熔层厚度影响最明显,脉冲宽度其次,脉冲间隔影响最弱。基于试验结果形成从圆度、锥度、孔内壁粗糙度、孔内壁形貌、重熔层厚度分布、重熔层组织结构、重熔层成分等多角度表征气膜孔损伤的方法。利用多处测量正交计算和极差的方法,以及面积方法评价不同打孔工艺重熔层厚度,剖析重熔层的形成过程,分析出电火花打孔对先进单晶高温合金的损伤机理。     

气膜孔扩散结构分块成形加工中伺服轨迹修正算法优化

气膜冷却孔用于保证航空发动机涡轮叶片在高温、高压环境下工作。带有复合角出口扩散结构的气膜冷却孔具有更好的冷却性能。采用棒状方形截面电极的电火花分块成形加工扩散结构是一种气膜孔加工新方法,具有工具电极成本低、工作液易于更新和可连续加工的工艺优点。针对电火花分块成形加工中保持微小放电间隙时的工具电极三维空间伺服进给轨迹误差问题,提出了加工轨迹误差修正算法,并通过实验重点优化了算法参数。典型气膜冷却孔加工的结果验证了轨迹修正算法可提高精度的有效性。     

电火花加工航空发动机燃烧室多层气膜孔

在高推重比航空发动机的研制中，许多零件上要加工多层气膜孔。如某机燃烧室工作温度在８５０℃以上，其内外壁上有８０００多个１．０～２．０ｍｍ的多层均匀分布的气膜孔进行冷却，气膜孔的位置、孔向和孔径的精度直接影响发动机的工作性能。加工气膜孔的发动机零件属薄壁件，材料硬度高，气膜孔孔径小，孔数多，需采用电火花加工。英国产ＲＤ１－Ａ型电火花机床具有电火花打孔和磨削两种功能。经过大量的工艺试验和ＥＤＭ参数优选，用ＲＤ１－Ａ型电火花机床对环形多层气膜孔进行电火花加工，其位置精度、表面粗糙度和变质层厚度等均满…     

变截面异型孔激光精密加工技术研究

某型号导弹用涡扇发动机火焰筒头罩材料为高温合金。为了保证高温部件正常工作,在头罩上需要加工大量气膜孔冷却,冷却孔分布密集,孔径精度要求高,孔的轴线多为空间方向。通过开展激光加工参数控制研究,激光焦点位置定位研究,多轴激光加工编程技术研究,解决了空间密集气膜冷却孔的加工难题。     

涡轮叶片气膜孔制造及检测技术发展与展望

涡轮叶片作为航空发动机最核心的热端部件,在叶身加工气膜冷却孔是提高叶片承温能力的必然趋势。目前主流制孔工艺方法包括电火花加工（EDM）、电化学加工（ECM）与激光加工。其中,电火花制孔工艺最成熟,成本效率优势最为明显,广泛应用于多种型号叶片;电化学制孔可以满足“无重熔层、无微裂纹、无热影响区”的孔壁质量验收要求,但对异型孔加工能力不足限制其应用前景;长脉冲激光主要应用于静子件及燃机叶片的制孔,近些年随着超快激光技术的迅猛发展,孔壁加工精度及质量得到显著提升,使其在叶片转子件的制孔中也获得应用。此外,采用磨粒流、磁力研磨等气膜孔后处理工艺可消除孔口相贯线锐边,避免应力集中效应导致锐边起裂。目前,气膜孔检测技术的工程化应用滞后于加工技术,但对于叶片制孔质量控制与验收标准制定具有重要意义,亟需建立相关标准将先进测试表征方法应用于工程生产中,并长期助力智能制造技术发展。     

等离子喷涂-物理气相沉积制备热障涂层对气膜冷却孔的影响

目的研究等离子喷涂-物理气相沉积(PS-PVD)制备热障涂层过程中影响气膜冷却孔堵塞情况的因素。方法采用等离子喷涂-物理气相沉积技术,以团聚烧结的ZrO_2-7%Y_2O_3(7YSZ)为原料,在预制有气膜冷却孔的高温合金板基体上制备热障涂层,研究了气膜冷却孔的孔角度、孔径大小等参数在热障涂层制备过程中对气膜孔堵塞情况的影响。结果当气膜冷却孔的孔径控制为0.85 mm时,30°、60°、90°气膜冷却孔的孔径收缩率分别为19.01%、14.50%、14.86%,孔径收缩率随角度的增大而减小,一定程度后保持稳定。孔内部涂层结构与表面涂层结构一致,都为柱状结构涂层。当气膜冷却孔的角度控制为30°时,孔径为1.0、1.3、15 mm的气膜冷却孔的孔径收缩率分别为36.40%、31.70%、24.45%,孔径收缩率随孔径的增大而减小。涂层在孔内的分布深度随孔径大小的增大而增大。结论气膜冷却孔的角度会影响PS-PVD热障涂层的沉积效率,从而影响孔径收缩率。气膜冷却孔的孔径不影响PS-PVD热障涂层的沉积效率,但会影响孔径收缩率。     

复层气摸孔的电火花加工技术

介绍某高精度航空发动机燃烧室复层气膜孔的电火花加工技术。通过采用RD1－A型多电极数控电火花加工机床，优选EDM参数，有效地提高了气膜孔的加工质量和效率。     

复层气膜孔的电火花加工技术

介绍某高精度航空发动机燃烧室复层气膜孔的电火花加工技术.通过采用RD1-A型多电极数控电火花加工机床,优选EDM参数,有效地提高了气膜孔的加工质量和效率.     

涡轮叶片电加工孔重熔层控制及去除方法

涡轮叶片进行电火花加工时,加工表面会产生残留物,这些残留物即为零件加工表面的重熔层。通过对重熔层产生的原因分析和电火花加工工艺的控制,得到了减小重熔层厚度及去除重熔层的方法。该方法可推广到其他要求重熔层小或无重熔层的航空零件加工中。     

低盐溶液电火花-电解复合加工微小方孔试验

综合电火花加工快速蚀除材料与电解加工溶解重铸层的优势,提出了在低电导率的NaNO3溶液中使用电极逐层往复式铣削加工微小方孔的电火花-电解复合加工方法,并研究了电解液浓度、电压和电容参数对微小方孔加工质量的影响。结果表明:电解液浓度与加工电压对微小方孔加工质量影响较大,电容影响相对较小。选用最优加工参数在100μm厚的321不锈钢片上加工微小方孔,得到的方孔加工质量好、侧壁表面无重铸层,且工具电极相对损耗仅0.05%。     

微细电火花加工及表面重铸层电解去除装置的设计

微细电火花加工工件表面的重铸层影响加工精度和使用性能,为此设计了具有微细电火花加工及电解去除表面重铸层功能的集成装置。该装置由运动平台、伺服控制、脉冲电源等关键部分组成,集成了微细电火花和微细电解加工功能。针对不同加工方法采用不同的控制策略,解决了微细电火花加工与电解加工在同一设备上的集成问题。通过实验验证,该装置可以很好地实现微细电火花加工表面重铸层的在线去除,且去除厚度可通过改变加工参数的形式来控制。     

镍基高温合金脉冲电弧加工表面完整性研究

研究脉冲电弧加工镍基高温合金表面微观形貌,包括变质层厚度及特征、加工表面粗糙度、显微硬度,综合考虑以上各方面,研究脉冲电弧工作时,脉冲频率、占空比两种加工参数对表面变质层完整性的影响规律,得出频率和占空比较高时更容易产生裂纹,较低的频率和占空比会使熔化凝固层的厚度提高。     

Quantification of surface damage of tool steels after EDM

The surface transformation and damage in AISI O1, A2, D2 and D6 tool steels after EDM were investigated. The results show that the recast layer is composed of two distinct layers: a topmost layer solidifying inwards from the specimen surface and an intermediate layer solidifying outwards from the base of the molten metal. The depth of surface cracks is found to correlate well with the thickness of the white layer, the latter being a layer of rapidly solidified material which, depending on the tool steel material, may consist either primarily of the topmost recast layer, or both the topmost and a large part of the intermediate recast layer. The density of surface cracks, however, correlates better with the thickness of the overall recast layer.

Attempts were made to quantify the depth of white (or damaged) layer with respect to the process parameters and surface roughness after EDM. It is found that with a fixed dielectric and flushing condition, the damaged layer correlates well with the pulse energy irrespective of thetool steel material. On the other hand, even though the thickness of the white layer increases with the surface roughness, the result shows considerably more scatter. Based on the present findings, ways of estimating the depth of the damaged layer produced by EDM are proposed.     

Femtosecond laser machining of cooling holes in thermal barrier coated CMSX4 superalloy

Machining of cooling holes on thermal barrier coated superalloy components using a nanosecond (ns) laser generates considerable collateral damage such as recast layer, spatter and delamination of the ceramic coating. However, recent studies have suggested that these damages can be virtually eliminated by machining with femtosecond (fs) lasers. A detailed study on the microstructural characteristics of fs laser machined holes with diameters of 300 μm and 600 μm, generated on thermal barrier coated superalloy CMSX4 under various processing conditions has been conducted. Features examined include the shape, size and the surface finish of the hole wall. Femtosecond laser machined holes with a surface roughness of less than 2 μm and no major collateral damage could be generated in coated samples up to a thickness of 1.5 mm. The machining was found to cause minor ablative material removal from the top ceramic layer within 100 μm of the outer edge of the hole. The presence of machined holes did not affect the thermal cycling life at 1100 °C of the coated samples.     

Effect of beam angle on HAZ, recast and oxide layer characteristics in laser drilling of TBC nickel superalloys

Industrial applications of laser drilling include the production of cooling holes at acute angles in certain parts of the aero-engine components. These parts are often covered with ceramic thermal barrier coatings (TBC) to protect them from reaching excessive temperatures in hot engine environments. Acute angle TBC drilling brings three major simultaneous complications to the process. These are: (i) multi-layer drilling, (ii) non-symmetrical geometry and melt ejection, and (iii) increased depth of drilling. In a previous investigation by the authors, delamination of TBC was found as a main problem of angled drilling and mechanisms involved were studied. In the present study, implications of these difficulties on the hole quality is investigated through a comparative study of vertical and acute angle drilled holes. Characteristics of recast layer, heat-affected zone (HAZ), oxide layer and TBC delamination are investigated. Variation of these metallurgical characteristics with the depth of the hole is evaluated. Results for vertical and inclined holes are compared. The extent of HAZ, recast layer and oxide layer is seen to vary significantly with location and is found increasing with decreasing drilling angle to surface. Numerical simulation of pulsed laser heating of TBC Nimonic 263 was carried out for acute angle drilling with assist gas considerations. Results from the simulation suggested that the total heat transfer rate is higher on the leading edge side than the trailing edge of the heated region. Experimentally observed larger HAZ on leading edge side and larger recast layer on trailing edge side are explained by the analysis of heat flow characteristics obtained with the model.     

纳秒脉冲激光对表面织构参数影响研究

表面微织构具有良好的减摩作用,刀具表面微织构的应用受到国内外学者的广泛关注。针对激光技术在表面微织构制备中的应用,利用红外脉冲纳秒激光雕刻机在YT15刀片表面制备出单脉冲织构、连续线性凹槽织构,分析单脉冲功率及相邻两脉冲光斑重叠面积百分比对织构参数的影响。结果表明:随着激光功率的增加,单脉冲织构的直径、深度、重铸层高度、重铸层宽度均增加;随着相邻两脉冲光斑重叠面积百分比增加,连续线性凹槽织构的深度、宽度、重铸层高度均增加,而重铸层宽度减小;与同功率单脉冲织构相比,连续脉冲的织构深度、重铸层高度、重铸层宽度均大于单脉冲织构,连续脉冲的织构宽度小于单脉冲织构直径。该研究为特定尺寸表面微织构制备提供参考。     

AZ91D镁合金微弧氧化工艺参数的优化

利用自制微弧氧化装置在硅酸盐体系中对AZ91D镁合金进行微弧氧化处理.采用4因素3水平正交试验,从考察膜层厚度、表面粗糙度和耐蚀性出发,确定了AZ91D镁合金在硅酸盐体系中的最佳工艺参数.结果表明：在最佳工艺条件下,微弧氧化膜呈多孔结构、孔径较小,裂纹较少,分布均匀,膜层较为致密;微弧氧化膜由MgO、Mg2SiO4、MgAl2O4和少量的SiO2组成;室温下,在质量分数为3.5%的NaCl中性溶液中浸泡168 h后,膜层表面未出现明显的点蚀现象,耐蚀性较镁合金基体有了很大提高.