【摘要】：釕(Ru)作為鎳基高溫合金發(fā)展過程中的關鍵元素,其在合金中的作用備受關注。大多數(shù)研究主要針對含Ru的單晶高溫合金,但對于含Ru的多晶鎳基高溫合金的研究罕見報道。本文將系統(tǒng)研究Ru對多晶鎳基高溫合金的組織、合金元素偏析、凝固過程、密度、硬度、顯微疏松和熱腐蝕性能影響。采用真空熔模鑄造制備實驗合金和涂鹽腐蝕方法研究合金熱腐蝕性能。利用光學顯微鏡、電子掃描電鏡、電子探針、差熱分析系統(tǒng)等設備進行檢測和分析合金的相組成分布、偏析行為、凝固過程、腐蝕機理。通過研究發(fā)現(xiàn)合金鑄態(tài)組織主要由γ相、γ'相、γ/γ'共晶和MC型碳化物組成。隨著Ru含量增加,合金的鑄態(tài)組織枝晶干和枝晶間的γ'體積分數(shù)和尺寸均減小,γ'正方度和共晶的面積分數(shù)逐漸增加。合金經(jīng)過熱處理后,初生的γ'和共晶組織完全溶解,合金的相組成為γ相、γ'相和MC型碳化物。熱處理后合金中的γ'體積分數(shù)及尺寸隨著Ru的添加而減小。隨著Ru含量的增加,合金的密度增大,硬度提高,合金中的疏松減少。Ru的添加有益于抑制合金鑄造過程中疏松形成。Ru的添加改變了Cr、Mo的偏析特性,即從負偏析元素轉變?yōu)檎鲈?同時促進W的偏析程度。隨著Ru含量的增加,正偏析元素Ta、Ti的偏析程度增加但Al的偏析程度減小,Ru略偏析于枝晶間。Ru的加入降低了γ'初始溶解溫度和合金的固相線溫度,但對合金的液相線溫度沒有影響。隨著Ru的加入,合金終凝溫度(tf)和γ'析出溫度(tpγ')降低,凝固溫度區(qū)間(?t′)變寬。在900℃涂覆75%Na2SO4+25%Na Cl混合鹽的同等條件下,0Ru合金的抗熱腐蝕性能最差,隨著Ru含量的增加,合金抗腐蝕性能增強。4種不同Ru含量合金的熱腐蝕進程按照硫化-氧化機理進行。高Cr無Re多晶鎳基高溫合金中加入Ru元素有益于提高合金的抗熱腐蝕能力。
[Abstract]:As a key element in the development of nickel-based superalloys, ruthenium (Ru) has attracted much attention. Most of the studies are focused on single crystal superalloys containing Ru, but few studies on polycrystalline nickel based superalloys containing Ru are reported. In this paper, the effects of Ru on the microstructure, segregation, solidification, density, hardness, microporosity and hot corrosion of polycrystalline nickel based superalloys are systematically studied. The hot corrosion properties of the alloy were studied by vacuum investment casting and salt corrosion. The phase composition distribution, segregation behavior, solidification process and corrosion mechanism of the alloy were detected and analyzed by optical microscope, electron scanning electron microscope, electron probe and differential thermal analysis system. It is found that the as-cast microstructure of the alloy is mainly composed of 緯 phase, 緯 'phase, 緯 / 緯' eutectic and MC type carbides. With the increase of Ru content, the volume fraction and size of 緯 'between dendrite and dry dendrite in as-cast microstructure decreased, and the 緯' square degree and eutectic area fraction increased gradually. After heat treatment, the primary 緯 'and eutectic structure were completely dissolved, and the phase composition of the alloy was 緯 phase, 緯' phase and MC type carbide. After heat treatment, the volume fraction and size of 緯'in the alloy decreased with the addition of Ru. With the increase of Ru content, the density of the alloy increases, the hardness increases, and the porosity decreases. The addition of Ru is beneficial to restrain the formation of porosity. Ru in the casting process of the alloy changes the segregation characteristics of Cr,Mo. That is, from negative segregation element to positive segregation element, and to promote the segregation degree of W at the same time. With the increase of Ru content, the degree of segregation of positive segregation element Ta,Ti increases, but the degree of segregation of Al decreases. The addition of Ru to the intergranular phase decreases the initial dissolution temperature of 緯 'and the solid-state line temperature of the alloy. However, there is no effect on the liquid line temperature of the alloy. With the addition of Ru, the final setting temperature (tf) and 緯 'precipitation temperature (tp 緯') of the alloy decreased, and the solidification temperature range (t') became wider. The thermal corrosion resistance of 0 Ru alloy was the worst under the same condition of 75%Na2SO4 25%Na Cl mixed salt coating at 900 鈩，

本文編號：2217149