Size and Shape Effects for Gamma Prime in Alloy 738

Cast IN-738 and wrought Inconel 738 are generic applications for most metallurgical designers of gas turbine blades in the Power Generation Industry on a worldwide basis... Particularly, where first stage buckets are concerned. This is the case because both alloy types exhibit outstanding creep and stress rupture properties to provide an extended service period in a harsh environment. Typically, Alloy 738 is fired in the turbine at 1970 °F (1074 °C) which is about 0.9T _m where T _m represents the melting temperature... A very demanding service temperature, indeed. Furthermore, Alloy 738 is expected to endure this high temperature for a duration of 26,000 h at base load before being retired (R) or replaced (R′) or reused (R′′) issues are ever considered. When these three (3) problems (R-R′-R′′) are brought before a given Materials Review Board for appropriate debate, many pro and con arguments are always evident because (1) Gas turbine blades are not inexpensive and (2) The threat of field failures with possible product liability litigation is of maximum interest to all gas turbine repair shop personnel. The intent of this paper is show how gamma prime precipitate particles can be better examined and more efficiently evaluated using a new characterization method. This research is offered as a contribution to the sum of total knowledge.     

循环热处理细化TiAl晶粒

探讨了循环热处理技术在细化ＴｉＡｌ合金晶粒方面的应用。研究表明,粗大的铸态组织）约５００μｍ的全层状组织）经块型转变预处理后,在α转变温度进行６次以上的快速加热－冷却处理,可以显著地细化晶粒。由此还可以制备出２０μｍ的细小全层状组织。晶粒细化的原因是进行快速循环相变破坏了组织跗以及新旧闰向关系。影响细化效果的主要因素有;加热速度、保温时间、冷却速度和循环次数。     

某航空发动机用GH738材料热处理工艺探讨

GH738是以γ'相沉淀硬化的镍基高温合金,为航空发动机高温紧固件用料[1].目前采用的热处理工艺为:固溶,1020℃/4 h/油冷;时效,850℃/4 h/通氩气开风扇冷却.760℃/16 h/通氩气开风扇冷.在此工艺下,时常出现零件硬度偏高、高温持久性能偏低等质量问题.通过对GH738进行大量的热处理工艺试验及试验数据分析,表明该材料在:固溶1040℃/4 h/油冷、时效850 ℃/4 h/通氩气开风扇冷却、760℃/16 h/通氩气开风扇冷的工艺路线下,所获得的零件强度、硬度和高温持久性能符合相应标准[2],稳定性好,满足了实际生产要求,为航机生产提供了更为合理的热处理工艺方法.     

Kinetics and Microstructural Investigation of High-Temperature Oxidation of IN-738LC Super Alloy

The present study was carried out to investigate the kinetics and the surface chemistry of the oxide layers formed on the IN-738LC super alloy during high-temperature oxidation at 950 °C in air from 1 to 260 h. Oxidation kinetics were studied by mass gain measurement. The oxide layers were characterized by field emission scanning electron microscope, elemental distribution map, energy-dispersive spectroscopy as well as x-ray diffractometry (XRD). The oxidation kinetics followed the parabolic law. The XRD analysis revealed that the oxide scale contained mainly NiO, Ni (Cr, Al)₂O₄, Al₂O₃, TiO₂ and Cr₂O₃. The oxide structure, from the top surface down to the substrate, was clarified by elemental map distribution studies as Ni-Ti oxides, Cr-Ti oxides, Cr₂O₃ oxide band, Ni-Co-Cr-W oxide and finally a blocky Al₂O₃ region. The oxidation scales were composed of three distinct layers of the outer and mid layers enriched by TiO₂ and Cr₂O₃, NiCr₂O₄ oxide, respectively, and the innermost layer was composed of Al₂O₃ and matrix alloy. The depleted gamma prime layer was formed under the oxidation scales due to the impoverishment of Al and Ti which were induced by the formation of Al₂O₃ and TiO₂.     

热处理过程中集成电路用弥散颗粒增强铜合金的变形行为研究

采用真空氧化压制法制备集成电路用弥散颗粒增强铜合金,研究其硬度和微观组织,并利用热模拟机对其变形行为进行研究和分析。结果表明,弥散颗粒增强铜合金的硬度可达到161 HV。变形温度为600~950℃,变形速度为0.001~1.000 s-1条件下,该铜合金的应力随着应变的增大呈现先增大后减小的趋势,最后趋于稳定值。     

真空热处理对NiCrAlY涂层／钛合金基体体系的影响

采用电弧离子镀(AIP)技术在耐热钛合金(近TC6)基体表面沉积制备NiCrAIY涂层.通过OM、SEM与EDS、XRD分析研究不同真空热处理制度对NiCrAlY涂层/钛合金基体体系的影响.结果表明:经650℃真空热处理后,NiCrAlY涂层中开始有γ'-Ni3Al相析出,750℃时含量增加,870℃时含量明显减少;从650℃开始,NiCrAlY涂层/钛合金基体开始发生界面反应,随着温度的升高,界面分层并加厚同时出现裂纹,在870℃下,NiCrAlY涂层,钛合金基体界面由外至内出现Ni3(Al,Ti)、TiNi和Ti2Ni中间化合物层;在750℃下,主要发生了Ni、Ti元素的扩散,Cr元素在870℃开始发生扩散.当温度升高到950℃时,由于Ni、Ti元素大量互扩散导致宏观疏空带出现,同时在基体和界面反应层交界处出现裂纹,这些都将引起涂层的退化失效.     

高温合金GH416薄壁管材真空热处理

研究了高温合金GH4 16薄壁材料的真空热处理工艺。根据材料要求的表面质量、晶粒度和力学性能等优化工艺参数 ,实现高质量的热处理。     

真空技术和真空热处理实用数据

术语 (1) 平均自由程 mean free path 气体或蒸气分子相互碰撞前飞行的平均距离. (2) 分子流 molecular flow 气体或蒸气通过管道时,如果管道通行截面的最大内径小于平均自由程,这时的气体流动称之谓分子流.     

某压力容器焊接附件的真空热处理

某压力容器的本体和附件均采用D406A（30Si2MnCrMoVE）钢制作,但经真空热处理后附件硬度达50HRC左右,难以机加工。为了尝试用其他材料制造该附件,分别用30钢、45钢和30CrMnSiA钢及H10、H08和H18焊丝与D406A钢焊接,研究了焊接试样按D406A钢工艺真空热处理后的显微组织和力学性能。结果表明,30CrMnSiA钢与D406A钢用H10焊丝焊接的试样经930cC真空加热和2×10^5Pa压力气淬后,硬度为35～40HRC,抗拉强度为1100～1200MPa,无过热组织,达到了要求。     

Heat Treatment of Tools in Vacuum

Metal Science and Heat Treatment -     

DZ4合金在高压气淬真空炉中的热处理

在真空高压气淬炉中，对ＤＺ４合金以不同压力冷却进行固溶处理，从中找出最佳压力为０．０５－０．２ＭＰａ，其固溶温度，时间及时效Ａ怀常规工艺相同     

Ag—Cu—Zr合金的热处理

报道Ag—Cu—Zr合金的固溶时效热处理制度的选择。     

铝合金型材热挤压模具的热处理

根据铝合金型材热挤压模具的工作条件及失效形式，通过试验，采用硼、碳、氮共渗并淬火、回火处理，来提高其使用寿命，获得了良好的效果。     

AZ91D镁合金金属型锭料尺寸变化对等温热处理组织的影响

以AZ91D镁合金为实验原料,经重熔后浇注成不同尺寸(直径)的锭料;研究了金属型锭料尺寸变化对等温热处理组织的影响.结果表明,AZ91D镁合金锭料经等温热处理后,其心部逐渐到边缘的组织存在较大的差异,初生相颗粒尺寸由大逐渐减小,颗粒由块状趋于圆整并且分布均匀,液相也渐渐增多.随AZ91D镁合金锭料尺寸增加,等温热处理发现由锭料心部逐渐到边缘的组织存在的差异将进一步增加,并且锭料初生颗粒及固相率有增大趋势.     

真空热处理对W—7Ni—3Fe高密度合金力学性能的影响

研究了真空热处理对Ｗ－７Ｎｉ－３Ｆｅ高密度合金力学性能的影响。结果表明，真空热处理可使合金试样的抗拉强度及伸长率显著提高，但对冲击韧度影响不大。通过对合金试样断口形貌的扫描电镜（ＳＥＭ）观察及对试样断口表面合金元素价态的Ｘ射线光电子能谱（ＸＰＳ）分析，探讨了真空热处理对合金力学性能影响的机理。     

真空热处理对微波烧结93W-Ni-Fe合金显微组织及力学性能的影响

研究真空热处理对微波烧结挤压棒坯93W-Ni-Fe合金显微组织及力学性能的影响,采用高倍SEM和光学金相分别对合金断口和显微组织进行观察,采用能谱分析仪对合金真空热处理前后各元素含量进行定量分析,并对真空热处理样的相对密度、抗拉强度、延伸率和硬度进行测定和分析.结果表明:经真空热处理后,钨合金的各项力学性能都得到了提高,抗拉强度和延伸率提高显著,抗拉强度从920 MPa提高到了988 MPa,延伸率从9.7％提高到了18.6％;真空热处理后,显微组织中钨晶粒的连接度降低,合金断口中钨晶粒的穿晶解理断裂和粘结相的延性撕裂增多;真空热处理后合金粘结相中的钨含量明显降低.     

Heat Treatment Development for a Rapidly Solidified Heat Resistant Cast Al-Si Alloy

Existing heat treatment standards do not properly define tempers for thin-walled castings that solidified with high solidification rates. Recently emerged casting processes such as vacuum high pressure die casting should not require long solution treatment times due to the fine microstructures arising from rapid solidification rates. The heat treatment studies involving rapidly solidified samples with secondary dendrite arm spacing between 10 and 35 μm were conducted for solution times between 30 min and 9 h and temperatures of 510 and 525 °C and for various aging parameters. The metallurgical analysis revealed that an increase in microstructure refinement could enable a reduction of solution time up to 88%. Solution treatment resulted in the dissolution of Al₂Cu and Al₅Mg₈Si₆Cu₂, while Fe- and TiZrV-based phases remained partially in the microstructure. The highest strength of approximately 351 ± 9.7 and 309 ± 3.4 MPa for the UTS and YS, respectively, was achieved for a 2-step solution treatment at 510 and 525 °C in the T6 peak aging conditions, i.e., 150 °C for 100 h. The T6 temper did not yield dimensionally stable microstructure since exceeding 250 °C during in-service operation could result in phase transformation corresponding to the over-aging reaction. The microstructure refinement had a statistically stronger effect on the alloy strength than the increase in solutionizing time. Additionally, thermal analysis and dilatometer results were presented to assess the dissolution of phases during solution treatment, aging kinetics as well as dimensional stability.     

粗晶碳化钨粒度对WC-Co合金晶粒度的影响

选用供应态分别为30μm和12μm的二种粗颗粒WC粉末,研究不同方法表征的粉末粒度与合金晶粒度的关系。结果表明:三种粉末粒度测定方法给出的结果都呈现粒度越粗合金的晶粒度也越粗的规律。粗颗粒WC的研磨态粒度与合金的晶粒度相当接近,金相法测得的12μmWC的晶粒分布与所制备的合金的晶粒度的一致性比30μmWC制备的合金要好。粗晶WC研磨态的Fsss粒度可以用于评价粗晶WC晶粒度,也可以预测WC-Co合金的晶粒度。     

自生Mg2Si颗粒增强过共晶Al-18%Si合金的热处理工艺研究

在分析稀土对初晶硅、共晶硅及Mg2Si相结晶行为影响的基础上，通过正交试验方法，对合金Al-18％Si-Mg合金的最佳热处理工艺进行了研究。用扫描电镜与金相显微镜观察了不同热处理工艺制度（固溶与时效制度）下过共晶Al-18％Si-Mg合金的显微组织，并通过测试相应的力学性能，分析得出了该合金的最佳热处理工艺参数。     

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