【摘要】：隨著鎳基單晶高溫合金難熔元素的增加,初熔溫度的提高,對鎳基單晶葉片制備用陶瓷型殼提出更高的要求,因此,“薄壁高強(qiáng)”陶瓷型殼的制備已成為制約新一代單晶渦輪葉片研制的關(guān)鍵技術(shù)。本文采用礦化劑和短切碳纖維制備了復(fù)合改性型殼,并通過正交試驗(yàn)法研究了礦化劑的添加量、短切碳纖維的添加量和長度對型殼試樣的濕強(qiáng)度、燒結(jié)強(qiáng)度和高溫自重變形的影響,探究了燒結(jié)溫度對型殼試樣的燒結(jié)強(qiáng)度和抗變形能力的影響,及型殼試樣與不同配方和燒結(jié)工藝的陶瓷型芯的連接強(qiáng)度,最后,利用ProCAST軟件模擬單晶定向凝固過程中復(fù)合改性型殼緣板處的溫度場,并通過定向凝固實(shí)驗(yàn)研究復(fù)合改性型殼對新型低錸鎳基高溫合金單晶鑄件的宏觀、微觀組織的影響。型殼力學(xué)性能研究表明:在型殼試樣濕強(qiáng)度的影響因素中,短切碳纖維的添加量是主要因素,短切碳纖維的長度是次要因素,而礦化劑的添加量作用最小,得到的工藝優(yōu)化配方依次分別為0.5g/ml、3mm和2%,復(fù)合改性型殼試樣較普通電熔剛玉型殼的濕強(qiáng)度從1.02MPa最大可提高到1.58MPa。在型殼試樣燒結(jié)強(qiáng)度的影響因素中,礦化劑的添加量是主要因素,短切碳纖維的添加量是次要因素,而短切碳纖維的長度作用最小,得到的工藝優(yōu)化配方依次分別為6%、0.5g/ml和3mm,復(fù)合改性型殼試樣較普通電熔剛玉型殼試樣的燒結(jié)強(qiáng)度從7.79MPa最大可提高到11.63 MPa。在型殼試樣抗變形能力的影響因素中,礦化劑的添加量影響最大,短切碳纖維的長度是次要因素,短切碳纖維的添加量作用較小,得到的工藝優(yōu)化配方依次分別為6%、5mm和0.3g/ml,復(fù)合改性型殼試樣較普通電熔剛玉型殼試樣的高溫自重變形量從1.25%最小可減到0.42%。綜合分析得出優(yōu)化后配方即礦化劑的添加量為6%、短切碳纖維長度和添加量分別為3mm和0.5g/ml。型殼的燒結(jié)溫度、型殼與陶瓷型芯連接強(qiáng)度研究表明:采用礦化劑和短切碳纖維的優(yōu)化配方制備的型殼試樣,分別在1000℃、1100℃和1200℃下燒結(jié),結(jié)果表明隨溫度的升高,試樣的燒結(jié)強(qiáng)度明顯提高,高溫自重變形量和線收縮率也不斷增大。當(dāng)燒結(jié)工藝相同時(shí),由于界面兩邊基體性質(zhì)相容而殘余應(yīng)力低,氧化鋁陶瓷型芯與試樣的界面連接強(qiáng)度更大;從燒結(jié)工藝可知,通過二次燒結(jié)后,界面組織致密且孔隙率低,二次燒結(jié)的陶瓷型芯與試樣界面連接強(qiáng)度更大。數(shù)值模擬與定向凝固實(shí)驗(yàn)表明:相比較于普通型殼,在數(shù)值模擬中復(fù)合改性型殼在葉片緣板處未出現(xiàn)過冷現(xiàn)象,降低了雜晶形成的可能性。壁厚較薄且均勻的復(fù)合改性型殼,加快了型殼的散熱效果,宏觀上,葉片緣板處減少了雜晶的生成;微觀上,復(fù)合改性型殼單晶鑄件的一次、二次枝晶間距分別為274.2μm和88.7μm,可見復(fù)合改性型殼單晶鑄件的一次、二次枝晶組織更加細(xì)密,單晶鑄件枝晶間的γ-γ′共晶相尺寸變小且連續(xù)性降低。
[Abstract]:With the increase of refractory elements and initial melting temperature of nickel base single crystal superalloy, higher requirements are put forward for ceramic mold shell for the preparation of nickel base single crystal blade. The preparation of thin wall high strength ceramic shell has become a key technology for the development of new generation single crystal turbine blades. In this paper, the composite modified shell was prepared by mineralizing agent and short cut carbon fiber, and the wet strength of the shell sample was studied by orthogonal test, including the addition amount of mineralizer, the addition amount and length of short cut carbon fiber. The effects of sintering temperature on the sintering strength and deformation resistance of shell samples, and the bonding strength of shell specimens with ceramic cores with different formulations and sintering processes were investigated, and the effects of sintering temperature on the sintering strength and deformation resistance of shell samples were investigated. The temperature field at the edge plate of composite modified shell during unidirectional solidification of single crystal was simulated by Procast software, and the effect of composite modified shell on macro and microstructure of new type low rhenium nickel base superalloy single crystal castings was studied by directional solidification experiment. The mechanical properties of the shell show that the addition of short cut carbon fiber is the main factor, the length of the short cut carbon fiber is the secondary factor, and the addition of mineralizer is the least, among the influencing factors of the wet strength of the shell sample, the content of short cut carbon fiber is the main factor, and the length of short cut carbon fiber is the secondary factor. The optimized formula is 0.5g / ml 3mm and 2mm respectively. The wet strength of composite modified corundum shell can be increased from 1.02MPa to 1.58MPa. Among the factors affecting the sintering strength of shell sample, the addition of mineralizer is the main factor, the addition of short cut carbon fiber is the secondary factor, and the length of short cut carbon fiber is the least. The optimized formula is 6 / 0. 5 g / ml and 3 mm respectively. The sintering strength of composite modified corundum shell is increased from 7.79 MPA to 11.63 MPA compared with that of conventional fused corundum shell. Among the factors affecting the deformation resistance of shell sample, the addition of mineralizer is the most important factor, the length of short cut carbon fiber is the secondary factor, and the addition amount of short cut carbon fiber is less. The optimized formulation is 6mm and 0.3 g / ml, respectively. The weight deformation of composite modified corundum shell is reduced from 1.25% to 0.42% compared with that of conventional fused corundum shell. After comprehensive analysis, the addition of mineralizing agent is 6, the length and amount of short cut carbon fiber are 3mm and 0.5g / ml, respectively. The sintering temperature of the shell and the bonding strength between the shell and the ceramic core show that the shell samples prepared by the optimized formula of mineralizer and short cut carbon fiber are sintered at 1000 鈩，

本文編號：2137630