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2010/12/20

Improving Aerospace Engines with Advanced Materials

分類:technologies
2010/12/20 08:52
Improving Aerospace Engines with Advanced Materials

Ceramics and Metal Alloys Survive High Temperatures

Advanced ceramics and high performance superalloys are playing an important role in improving aerospace engines as aerospace manufacturers look for high-temperature materials that increase performance, improve fuel efficiency and satisfy safety standards, while at the same time lowering manufacturing costs.



An example of superalloys available for high temperature braze repair applications are pre-sintered preforms, a customized blend of the superalloy base and a low melting braze alloy powder in either a plate form, specific shape, paste, or paint. PSPs are used extensively for reconditioning, crack repair and dimensional restoration of such aerospace engine components as turbine blades and vanes.



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2010/12/16

鎳基合金

鎳基合金是指在650~1000℃高溫下有較高的強度與一定的抗氧化腐蝕能力等綜合性能的一類合金。 按照主要主要性能又細分為鎳基耐熱合金,鎳基耐蝕合金,鎳基耐磨合金,鎳基精密合金與鎳基形狀記憶合金等。 高溫合金按照基體的不同,分為:鐵基高溫合金,鎳基高溫合金與鈷基高溫合金。 其中鎳基高溫合金簡稱鎳基合金
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2010/12/16

鎳基高溫合金

鎳基高溫合金
nickelbase superalloys


   以鎳為基體(含量一般大於50%)、在650~1000範圍內具有較高的強度和良好的抗氧化、抗燃氣腐蝕能力的高溫合金。
   發展過程  鎳基高溫合金(以下簡稱鎳基合金)是30年代後期開始研製的。 英國於1941年首先生產出鎳基合金Nimonic 75(Ni-20Cr-0.4Ti);為了提高蠕變強度又添加鋁,研製出Nimonic 80(Ni-20Cr-2.5Ti-1.3Al)。 美國於40年代中期,蘇聯於40年代後期,中國於50年代中期也研製出鎳基合金。 鎳基合金的發展包括兩個方面:合金成分的改進和生產工藝的革新。 50年代初,真空熔煉技術的發展,為煉製含高鋁和鈦的鎳基合金創造了條件。 初期的鎳基合金大都是變形合金。 50年代後期,由於渦輪葉片工作溫度的提高,要求合金有更高的高溫強度,但是合金的強度高了,就難以變形,甚至不能變形,於是採用熔模精密鑄造工藝,發展出一系列具有良好高溫強度的鑄造合金。 60年代中期發展出性能更好的定向結晶和單晶高溫合金以及粉末冶金高溫合金。 為了滿足艦船和工業燃氣輪機的需要,60年代以來還發展出一批抗熱腐蝕性能較好、組織穩定的高鉻鎳基合金。 在從40年代初到70年代末大約40年的時間內,鎳基合金的工作溫度從700提高到1100,平均每年提高10左右。 鎳基高溫合金的發展趨勢見圖1 [鎳基高溫合金的發展趨勢]

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2010/12/16

加工鎳基合金銑刀的特點

當遇到Hastelloy、waspaloy、 Inconel和Kovar等難加工材料時,加工知識與經驗就顯得非常重要。目前,鎳基合金的應用越來越 多,主要用於製造航太、醫療、化工行業的一些重要零件。這些材料具有很高的強度、耐腐蝕性,並能經受極高的溫度。在上述材料中加入了一些特殊元素,可獲得 優越的性能。但另一方面,也使這些材料變地特別難於銑削加工。

我們知道,在鎳系合金中鎳和鉻是兩個主要添加成分,增加鎳能增加材料韌性,加入鉻可提高材料的硬度,再加上其他成分的平衡,據此就可以預測刀具的磨損情況。

添加到材料中的其他元素可能有:矽、錳、鉬、鉭、鎢等,值得注意的是,鉭和鎢也是用來製造硬質合金的主要成分,它們能有效地提高硬質合金的性能,但是這些元素加入到工件材料中,就使它變地難以銑削加工,差不多像用一把硬質合金刀具切削另一把硬質合金刀具一樣。


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2010/12/16

國外高性能航空發動機製造技術發展趨勢

美國國防部1988 年在“ 綜合高性能渦輪發動機技術( IHPTET ) ” 計劃中提出了高推重比、高性能發動機結構質量減輕50% ,推重比提高100% 的發展目標。 高性能發動機在新材料結構、新結構方面具有顯著的特點,並且突破了傳統的設計觀念,由設計— 材料— 製造3 位一體實現高性能發動機的性能要求,材料和製造技術的貢獻率為50 % ~ 70% 。 預計在2015 ~ 2020 年將有可能研製出推重比為15 ~ 20 的渦扇發動機,它與目前使用的推重比8 發動機(如F100 )相比具有如下特點: 

( 1 )風扇由3 級減為1 級,葉片為帶彎掠的空心結構,可減重30% ; 
( 2 )壓氣機由9 級減為3 級,轉子為整體葉環結構,由鈦基複合材料製成,與傳統結構相比,可減輕質量70% ; 
( 3 )燃燒室火焰筒材料由耐熱合金改為陶瓷基複合材料; 
( 4 )高低壓渦輪均為單級的對轉結構,在仍採用金屬材料的條件下,整體葉盤結構可減重30% ;最終擬採用陶瓷基複合材料或抗氧化的碳/ 碳( C /C )複合材料,渦輪前溫度高達2200K 以上; 2=lI??TIEJ 
( 5 )由於渦輪進口溫度很高,即使按下限2200K 計算,發動機單位推力也比F100 高70% ~ 80% ,因而新發動機也可能不採用加力燃燒室; 
( 6 )尾噴管將採用固定結構的射流控制全方位矢量噴管。 
綜上所述,高性能航空發動機製造技術呈現以下發展趨勢: 
( 1 )輕量化、整體化、新型冷卻結構製造技術向低成本、高效率方向發展; 
( 2 )新材料構件製造技術出現較大突破; 
( 3 )新工藝技術成為現代航空發動機發展的重大關鍵製造技術,並得到廣泛應用; 
( 4 )在傳統製造技術基礎上發展起來的先進製造技術已成為支撐現代製造業的骨架和核心,以信息化帶動傳統製造業,企業信息化工程得到長足發展。 

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2010/12/12

Aerospace Surface Treatment - ECM

The ECM process can be used to machine any hardness of conductive metal, with key benefits being:

  • high metal removal rates up to 10mm/min
  • surface finishes up to 0.04ra
  • Extremely low tooling costs
  • Very low running costs
  • Zero burr creation
  • Cold processing with no machining affect to the material structure

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2010/12/12

Titanium and Titanium Alloys: Key Engineering Materials for

By Dr Thoguluva Raghavan Vijayaram PhD

Senior Lecturer Department of Manufacturing Process and System Faculty of Manufacturing Engineering, UTeM Universiti Teknikal Malaysia Melaka Ayer Keroh, 75450 Melaka Malaysia Email: vijayaram1@gmail.com

Titanium was first discovered in an impure form by Rev William Gregor in England, 1971. It was later given the name titanium (after the titans, in Greek Mythology, the sons of the sky and earth gods) by a German chemist, Martin Kloproth, when he found a dioxide of the metal in rutile, ilmenite, and in many other widely dispersed ores. In 1910, pure titanium was manufactured by M.A.Hunter, an American Chemist. Hunter was able to extract the metal from the ores and developed the process of mixing rutile ore, Titanium oxide with chlorine and coke, then applying extreme heat, producing titanium tetrachloride, which was further reduced with sodium to form titanium. The hunter process successfully produced high quality titanium. Dr Wilhelm Kroll, in 1946, developed the process currently used for producing titanium commercially. The Kroll process reduces titanium tetrachloride with magnesium. This multi-batch, high temperature process proves to be inefficient. It drives the price of titanium to the point where its applications are restricted to the high-priced, niche markets.

The Armstrong process, developed by International Titanium Powder, LLC is a method of making high purity, fine Titanium powder in a continuous process. This process operates at low temperature, in low pressure, and in a small volume equipment. So, capital cost and labor cost is greatly reduced. The product does not require the additional purification needed by sponge produced from the hunter or kroll process. The powder is suitable for various applications such as powder metallurgy, spray forming, and other near net shape processes. Small diameter, high purity powder is produced directly with now waste stream.

Eventhough titanium is in abundance in nature, it was not found until the 18th century that it was discovered. This can be explained based on the fact that titanium does not exist by itself but it is found in conjunction with other elements. It is found in the minerals ilmenite and rutile at quantities that it has proven economically profitable to produce them in large quantities while it is also extracted from minerals such as leucoxene, perovskite, brookite, sphene, and anatase.


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2010/12/10

ECM / PECM Technology: Improving engine blisk manufacturing

Improving engine blisk manufacturing 

Engineers at Sermatech International, Inc. have improved aircraft engine blisk manufacture through electrochemical machining (ECM). Sermatech-Lehr has been machining electrochemically for some time and has opened a new ECM facility in Cincinnati, OH for blisk production.

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The ECM process has three stages: forging (lower right), rough cut (lower left), and finished blisk.

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2010/12/09

燃燒室與渦輪

燃燒室
經過壓縮的高壓空氣中,由注油系統引進燃油使其燃燒,形成適合渦輪(Turbine)之高溫氣體。燃油在燃燒室(Combustion Chamber Burner)前端附近形成霧狀的燃燒圈,只有在發動機剛啟動時,須靠點火系統來點燃外,一經點燃,就靠火焰持續燃燒下去。這部份燃燒圈除可將壓縮機送來的氣流流速予以降低外,並可預防逆流或渦流(Swirl)火焰吹熄,還可保持空氣與燃油的混合比(以重量為單位),約在14~18:1間以提高燃燒速度。

燃燒圈的溫度部份可高達攝氏1600~2000度,如此高溫使得燃燒室本身的結構或渦輪材質無法承受,故須進行冷卻。通常的方式是將燃燒室的內襯筒(Liner)壁面開許多孔,讓原來由旁通過燃燒圈的空氣,經由這些開孔進入,如此除能冷卻壁面外,尚能降低燃氣的高溫。

經由這些方式,能將渦輪進氣溫度(TIT)降到適當值以下。燃氣並經由大量冷空氣稀釋的結果,綜合性的油氣燃燒比變成60~130:1,亦並非配合壓縮機來運送全部的空氣,注入燃油予以燃燒,而是在燃燒圈使用的空氣量(稱為一次空氣)只佔全部的20~30%,其他(二次空氣)皆用來當作冷卻之用。

若燃燒室和渦輪能承受更高溫度,可將油氣混合比調整,提高渦輪進氣溫度,以提升發動機熱效率及增加發動機推力。

燃燒室因長期暴露在高溫中,因此使用厚度為2mm左右,以鎳為主的海氏合金(Hastalloy)等超耐熱合金。也有部份發動機,再其燃燒室壁面施以陶瓷材料的耐熱塗佈(Thermalbarrier Coating)。而渦輪發動機的燃燒室分成下列三種。

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Inconel 718 Alloys


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The PECM Premium helps to shorten the process stream and to complete difficult tasks in the machining of metal components. 

Highlights:

  • Precision imaging in 2.5D
  • Great repeatability of lowering speeds
  • Surface finishes Ra 0.05 

The excellent repeatability of the PECM process on the Premium series is a result of the intelligent machine concept and our patented PECM technology.



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2010/12/09

EMAG PECM 精密電化學切削-- 航太渦輪葉片 inconel 718 Blisk 製造

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Inconel 718 Alloys




Electrochemical Metal Removal

The advantage: Electrochemical processes are very cost-effective methods of remov-ing material without building up residual stresses. They produce gentle transitions and smooth surfaces.

  • Electrochemical machining (ECM)
  • Electrochemical drilling
  • Pulsed electrochemical machining (PECM)

The advantage: Electrochemical processes are very cost-effective methods of remov-ing material without building up residual stresses. They produce gentle transitions and smooth surfaces.


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