CM 247 LC超合金微細晶鑄造特性及機械性質研究

Characteristics and Mechanical Properties of Fine-Grained CM 247 LC Superalloy Casting

10.6409/JMSE.200001.0170

黃信二(H. E. Huang)；顧鈞豪(C. H. Koo)；馬堅勇(C. Y. Ma)；李滄曉(T. S. Lee)

CM 247 LC超合金 ； 方向性凝固 ； 微細晶製程 ； 熱均壓 ； CM 247 LC Superalloy ； Directional Solidification ； Fine Grain Processes ； Hot Isostatic Pressing

材料科學與工程

32卷4期（2000 / 01 / 01）

170 - 178

繁體中文

本研究係以CM 247 LC超合金爲素材，以真空精密鑄造爐在控制澆鑄參數下，澆鑄成微細晶試桿。度件經熱均壓及真空熱處理後，量測其基本物性、化性及機械性質，以評估CM 247 LC超合金微細晶鑄造之可行性，並研究提昇微細晶鑄件機械性能之參數。研究結果顯示控制鑄造參數可達到晶粒細化之效果，晶粒尺寸可由傳統6~20mm之柱狀晶轉變爲80μm之等軸晶細晶。在常溫溫拉伸性質方面，CM 247 LC多晶度件晶粒細化可提高室溫之降伏強度及延伸率，降伏強度可由2~3mm柱狀晶之939 MPa提昇至80μm等軸細晶之1040 MPa，延伸率也由2~3mm柱狀晶之5.7%提昇至80μm等軸細晶之8.2%。在相同晶粒尺寸(80μm)下，CM 247 LC其常溫抗拉強度、降伏強度及延伸率都優於Mar-M247。在潛變測試方面，760℃/725 MPa及982℃/200 MPa測試條件下，CM 247 LC細晶試件(80μm)其潛變破斷壽命(55~73hrs及40~52hrs)遠高於規範EMS-55447(23hrs)，且延伸率也大幅提昇。本研究結果證實CM 247 LC超合金不但具有極佳之微細晶鑄造特性，並能提供較佳之強度及潛變性能。

An investigation on fine-grained casting process and mechanical behavior of CM 247 LC superalloy was carried out in this study. The alloy was remelted and cast to obtain the desired fine-grained test bars by controlling casting parameters. The objective of this study is to estimate the feasibility of producing a fine-grained CM 247 LC superalloy and improving its mechanical properties. After casting, the specimens were through the processes of hot isostatic press and vacuum heat treatment, then followed by the investigation of precipitation morphology, chemical and mechanical properties. The experimental results show that by controlling casting parameters the microscopic grains of CM 247 LC superalloy can be modified and refined from the conventional columnar grains of 6~20mm to the equiaxed grains of 80μm. Tensile test results reveal that the fine-grained test bars have higher yield strength and elongation than those of large grains. In addition, the tensile strength is increased from 939MPa for those test bars of 23mm column grains up to 1040MPa for those test bars of 80im fine grains. Similar results are obtained for increased elongation from 5.7% up to 8.2% when grain size is reduced down to Characteristics and Mechanical Properties of Fine-Grained cm 247 Le Superalloy Casting 80μm. Under the condition of same grain size (80μm), the CM 247 LC exhibits superior ultimate strength, yield strength and elongation than those of Mar-M247. According to creep test results, fine-grained CM 247 LC superalloy exhibits higher creep life (55~73hrs and 40~52hrs)and ductility than those values on EMS-55447 specification at 760°C1725 MPa and 982°C/200 MPa respectively. The results indicate that by well-controlling casting parameters the CM 247 LC superalloy has excellent castability to form a fine grain structure, high strength as well as superior creep resistance.