高强GH4738合金成分设计计算与验证

Composition Optimization Design and Verification for a Difficult Deformation Nikel Based Higher Strength Superalloy GH4738

摘要:

高强GH4738高温合金是超大功率烟气轮机/燃气轮机涡轮盘的候选材料,本文利用Thermo-Calc及JMatPro软件进行成分设计优化及拉伸强度预测进而实验验证。研究了不同C,Al,Ti及Cr等元素对该合金中相析出规律及其合金力学性能的变化规律；基于计算结果,制备了不同Al,Ti含量的GH4738合金,测试了其室温拉伸强度并对确定的超大型盘件用高强GH4738合金成分进行相分析研究。结果显示,C含量的增加,可促进碳化物M₂₃C₆及MC析出量的增加及其回溶温度的提高,但其对γ￠相含量的变化几乎无影响；Al,Ti含量的增加,都可明显提高合金γ￠相回溶温度及其析出量,并有利于合金拉伸强度的提高；Cr含量的增加,可提高γ￠相的回溶温度,但对其析出量影响不大；影响合金中γ￠相回溶温度及析出量的合金元素顺序依次为Al,Ti,Cr；高强GH4738合金成分设计原则为适当降低C含量,提高Al,Ti含量至合金成分范围高限；高强GH4738合金中γ￠相占约24.0%,其点阵常数为a₀=0.357~0.359nm,其组成结构为：(Ni_0.9236Co_0.0415Fe_0.0025Cr_0.0322)₃(Cr_0.0972Al_0.3585Ti_0.5059Mo_0.0366Cr_0.0018)。该研究结果为中国大尺寸GH4738难变形高温合金涡轮盘提供了的成分设计思路。

Abstract:

Super GH4738 superalloy has been chosen as a candidate alloy used for oversized turbine disc in gas turbine field. Thermo-Calc and JMatPro softwares were used to optimize composition of alloy combined with experiments. The effects of elements C, Al, Ti and Cr on phase precipitation and mechanical properties were calculated. Based on the calculated results, Several GH4738 superalloys with different contents of Al, Ti were melted and examined by tensile strength properties at room temperature and the final elements of super GH4738 superalloy were determined and its phases analysis were carried out. The results showed that increasing of C content can promote an increase of carbides( M₂₃C₆ and MC) and solution temperature, but it has almost no effect on the changes of γ￠ phase amount. Elements Al, Ti can significantly increase solution temperature and its amount for γ￠ phase and improve strength of GH4738 alloy. Solution temperature γ￠ phase would increase with increasing of element Cr, while almost no influence on precipitating γ￠ phase. The influence degree on solution temperature and amounts γ￠ phase for element were Al>Ti>Cr. The design principles of GH4738 super alloy was to reduce the C content, and improve Al, Ti content to the upper limit in the range of the alloy. The amount of super GH4738 alloy was about 24.0%, its lattice constant a₀=0.357-0.359 nm, its composition (Ni_0.9236Co_0.0415Fe_0.0025Cr_0.0322)₃ (Cr_0.0972Al_0.3585Ti_0.5059Mo_0.0366Cr_0.0018). The results would provide a guideline and design idea for large higher strength GH4738 superalloy turbine disk.