单晶定向凝固用复合改性型壳的工艺优化与性能研究
发布时间：2018-07-22 13:35
【摘要】：随着镍基单晶高温合金难熔元素的增加,初熔温度的提高,对镍基单晶叶片制备用陶瓷型壳提出更高的要求,因此,“薄壁高强”陶瓷型壳的制备已成为制约新一代单晶涡轮叶片研制的关键技术。本文采用矿化剂和短切碳纤维制备了复合改性型壳,并通过正交试验法研究了矿化剂的添加量、短切碳纤维的添加量和长度对型壳试样的湿强度、烧结强度和高温自重变形的影响,探究了烧结温度对型壳试样的烧结强度和抗变形能力的影响,及型壳试样与不同配方和烧结工艺的陶瓷型芯的连接强度,最后,利用ProCAST软件模拟单晶定向凝固过程中复合改性型壳缘板处的温度场,并通过定向凝固实验研究复合改性型壳对新型低铼镍基高温合金单晶铸件的宏观、微观组织的影响。型壳力学性能研究表明:在型壳试样湿强度的影响因素中,短切碳纤维的添加量是主要因素,短切碳纤维的长度是次要因素,而矿化剂的添加量作用最小,得到的工艺优化配方依次分别为0.5g/ml、3mm和2%,复合改性型壳试样较普通电熔刚玉型壳的湿强度从1.02MPa最大可提高到1.58MPa。在型壳试样烧结强度的影响因素中,矿化剂的添加量是主要因素,短切碳纤维的添加量是次要因素,而短切碳纤维的长度作用最小,得到的工艺优化配方依次分别为6%、0.5g/ml和3mm,复合改性型壳试样较普通电熔刚玉型壳试样的烧结强度从7.79MPa最大可提高到11.63 MPa。在型壳试样抗变形能力的影响因素中,矿化剂的添加量影响最大,短切碳纤维的长度是次要因素,短切碳纤维的添加量作用较小,得到的工艺优化配方依次分别为6%、5mm和0.3g/ml,复合改性型壳试样较普通电熔刚玉型壳试样的高温自重变形量从1.25%最小可减到0.42%。综合分析得出优化后配方即矿化剂的添加量为6%、短切碳纤维长度和添加量分别为3mm和0.5g/ml。型壳的烧结温度、型壳与陶瓷型芯连接强度研究表明:采用矿化剂和短切碳纤维的优化配方制备的型壳试样,分别在1000℃、1100℃和1200℃下烧结,结果表明随温度的升高,试样的烧结强度明显提高,高温自重变形量和线收缩率也不断增大。当烧结工艺相同时,由于界面两边基体性质相容而残余应力低,氧化铝陶瓷型芯与试样的界面连接强度更大;从烧结工艺可知,通过二次烧结后,界面组织致密且孔隙率低,二次烧结的陶瓷型芯与试样界面连接强度更大。数值模拟与定向凝固实验表明:相比较于普通型壳,在数值模拟中复合改性型壳在叶片缘板处未出现过冷现象,降低了杂晶形成的可能性。壁厚较薄且均匀的复合改性型壳,加快了型壳的散热效果,宏观上,叶片缘板处减少了杂晶的生成;微观上,复合改性型壳单晶铸件的一次、二次枝晶间距分别为274.2μm和88.7μm,可见复合改性型壳单晶铸件的一次、二次枝晶组织更加细密,单晶铸件枝晶间的γ-γ′共晶相尺寸变小且连续性降低。
[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，
本文编号：2137630
[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，
本文编号：2137630
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