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首頁> 外文學(xué)位 >The influence of electron beam welding parameters on heat affected zone and weld metal cracking of nickel-based superalloys.
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The influence of electron beam welding parameters on heat affected zone and weld metal cracking of nickel-based superalloys.

機(jī)譯：電子束焊接參數(shù)對鎳基高溫合金熱影響區(qū)和焊接金屬開裂的影響。

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Nickel-based Superalloys IN 738, Rene 80, and a proprietary single crystal material were studied in this project. These three alloys are commonly used in the hot section of gas turbine engines due to their excellent properties at elevated temperatures. In this study the influence of electron beam welding parameters on the cracking susceptibility of the alloys was investigated. The welding of the samples was performed at Bristol Aerospace located in Winnipeg, Manitoba. Focus coil current and welding speed were varied on samples of varying thicknesses of each alloy to simulate different types of blade repair. The total weld metal and heat affected zone (HAZ) crack lengths along with the weld and HAZ areas were measured using an optical microscope equipped with an image analysis system. The crack length per unit area, termed cracking index, was calculated and used to evaluate the cracking tendency of the alloy with respect to varying welding parameters. Orientation image microscopy was also used to determine if changes in crystal orientation were responsible for the cracking present in the single crystal and directionally solidified alloys. The experimental results showed that (1) The hardness of all three alloys can be reduced significantly by performing a special heat treatment called UMT. (2) IN 738 had a base microstructure of primary and secondary gamma' with intermetallics present. The microstructure of the post heat treated alloy consisted of coarsened primary and secondary gamma' plus the presence of M23C6 carbides. (3) The as-received microstructure of Rene 80 consisted of secondary gamma' along with a variety of carbides, borides and intermetallics. After heat treating the secondary gamma' was coarsened and M6C carbides were present. (4) The single crystal microstructure had very few phases present with only secondary gamma' and MC carbides visible. This is expected as fewer minor alloying elements are present as there is no need for grain boundary strengthening. Heat treating coarsened the gamma' phase. (5) Analysis of the cracking index of each alloy indicates that the welding parameters play a key role in determining the cracking susceptibility of the weld. The effects of focus coil current and welding speed on the cracking susceptibility are discussed. (6) The post weld microstructure of the directionally solidified and single crystal alloys have been analysed and the results tend to agree with the reports of other investigators.
機(jī)譯：本項目研究了鎳基超級合金IN 738，Rene 80和專有的單晶材料。這三種合金由于它們在高溫下的優(yōu)異性能而常用于燃?xì)鉁u輪發(fā)動機(jī)的熱區(qū)。在這項研究中，研究了電子束焊接參數(shù)對合金開裂敏感性的影響。樣品的焊接在位于曼尼托巴省溫尼伯的布里斯托爾航空航天公司進(jìn)行。在每種合金厚度不同的樣品上改變聚焦線圈電流和焊接速度，以模擬不同類型的葉片修復(fù)。使用配備有圖像分析系統(tǒng)的光學(xué)顯微鏡測量焊縫和熱影響區(qū)（HAZ）的總裂紋長度以及焊縫和HAZ區(qū)域。計算出每單位面積的裂紋長度，稱為裂紋指數(shù)，并用于評估合金在不同焊接參數(shù)下的裂紋傾向。取向圖像顯微鏡還用于確定晶體取向的變化是否導(dǎo)致單晶和定向凝固合金中出現(xiàn)裂紋。實(shí)驗結(jié)果表明：（1）通過執(zhí)行稱為UMT的特殊熱處理，可以顯著降低所有三種合金的硬度。 （2）IN 738具有主要和次要γ'的基本微觀結(jié)構(gòu)，并存在金屬間化合物。后熱處理合金的微觀結(jié)構(gòu)由粗化的一級和二級γ'以及M23C6碳化物的存在組成。 （3）Rene 80的微觀組織包括次級γ'以及各種碳化物，硼化物和金屬間化合物。在熱處理之后，將次級γ′粗化并且存在M 6 C碳化物。 （4）單晶微結(jié)構(gòu)幾乎沒有相，只有次級γ'和MC碳化物可見?？梢灶A(yù)期，因為不需要晶界強(qiáng)化，因此存在的微量合金元素較少。熱處理使γ′相變粗。 （5）對每種合金的開裂指數(shù)的分析表明，焊接參數(shù)在確定焊縫的開裂敏感性中起關(guān)鍵作用。討論了聚焦線圈電流和焊接速度對裂紋敏感性的影響。 （6）對定向凝固和單晶合金的焊后顯微組織進(jìn)行了分析，結(jié)果趨于與其他研究者的報告相吻合。

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