【摘要】：單晶高溫合金材料因其優(yōu)異的高溫性能,良好的抗氧化及抗腐蝕性能而成為制造先進(jìn)航空發(fā)動機(jī)、燃?xì)鉁u輪葉片的主要材料。隨著國內(nèi)外航空航天工業(yè)的發(fā)展,致使發(fā)動機(jī)的推重比不斷增大、渦輪入口溫度不斷提高、氣冷葉片結(jié)構(gòu)越來越復(fù)雜、壁厚越來越薄,產(chǎn)生所謂的薄壁效應(yīng)。因此,探究合金高溫持久壽命與壁厚效應(yīng)的的關(guān)系具有重要的意義,可以為預(yù)測發(fā)動機(jī)葉片的使用狀態(tài)與壽命提供強(qiáng)有力的依據(jù)。本文所選用的材料是由北京航材院提供的DD6鎳基單晶高溫合金,該合金為我國自主研發(fā)的一類新型第二代高溫合金。相比于國外使用的第二代單晶合金,DD6合金在高溫狀態(tài)下具有更加優(yōu)異的高溫持久性能。在980℃/250MPa的條件下,厚度為0.67mm、0.81mm和1.12mm的薄片狀試樣的持久壽命分別為185h、217.5h和229h。對葉片、鑄塊進(jìn)行顯微觀察,比較其枝晶間距、強(qiáng)化相形狀及尺寸等的差異,并通過測量其顯微硬度,確定能否用易獲得的試樣形式的持久性能數(shù)據(jù)表征葉片的持久性能。結(jié)果表明：葉片、鑄塊的宏觀形貌為枝晶組織,微觀形貌為立方狀的γ'強(qiáng)化相均勻的分布于γ基體上,兩種試樣的組織、硬度之間沒有顯著的差異。通過對比不同壁厚DD6試樣在980℃/250MPa高溫條件下的持久壽命,結(jié)合掃描電鏡、XRD、能譜、電子探針等試驗(yàn)方法對持久試樣斷口、近斷口橫截面和縱截面進(jìn)行形貌觀察和成分分析,探究DD6合金是否具有壁厚效應(yīng)并對其斷裂機(jī)理進(jìn)行分析。結(jié)果表明,DD6鎳基單晶高溫合金壁厚效應(yīng)并不明顯,隨著壁厚的減少,試樣高溫持久壽命略有降低,斷裂機(jī)理則是由韌性斷裂與脆性斷裂組合而成的混合型斷裂。試樣表面氧化膜的存在使試樣的有效橫截面積降低,進(jìn)而增加試樣的有效應(yīng)力,加上試樣縱截面微裂紋的存在及萌生于試樣亞表面及內(nèi)部的鑄造微孔,構(gòu)成試樣斷裂的基本原因。合金薄壁試樣的持久斷裂模式為“表面氧化-裂紋萌生-擴(kuò)展”和“內(nèi)部蠕變損傷”兩者綜合作用的結(jié)果。在“表面氧化-裂紋萌生-擴(kuò)展”和“整體蠕變損傷”兩者關(guān)系中,試樣蠕變程度越大,則壁厚效應(yīng)相對較��；相應(yīng)的,如果“表面氧化-裂紋萌生-擴(kuò)展”的作用大,蠕變的比重小,則壁厚效應(yīng)相對明顯。
[Abstract]:Single crystal superalloy has become the main material for the manufacture of advanced aero-engine and gas turbine blade because of its excellent high temperature performance, good oxidation resistance and corrosion resistance. With the development of aerospace industry at home and abroad, the propeller weight ratio of the engine is increasing, the inlet temperature of the turbine is increasing, the structure of the air-cooled blade is becoming more and more complex, the wall thickness is becoming thinner and thinner, resulting in the so-called thin-wall effect. Therefore, it is of great significance to explore the relationship between the high temperature rupture life and the wall thickness effect of the alloy, which can provide a powerful basis for predicting the service state and life of the engine blade. The material selected in this paper is the DD6 nickel base single crystal superalloy supplied by Beijing Aeronautical Materials Institute, which is a new type of second generation superalloy developed independently in China. Compared with the second generation single crystal alloy in foreign countries, the second generation single crystal alloy Candd6 has better high temperature rupture property at high temperature. At 980 鈩，

本文編號：2244285