基于热模锻造的FGH96粉末冶金高温合金晶粒细化工艺

Grain refinement process for power metallurgy superalloy FGH96 based on hot die forging

FGH96是我国第2代粉末冶金高温合金,采用常规锻造工艺进行开坯和成形极为困难,为了探索合理的细晶盘坯制备方法,在900℃的热模温度下,以不同应变速率、变形温度和变形量进行热模锻造实验,研究FGH96粉末冶金高温合金组织的变化规律。结果表明:当以低于γ′相固溶温度锻造时,随着变形温度的升高,显微组织更加均匀,当变形温度超过γ′相固溶温度时,晶粒有长大倾向;合金晶粒度随着变形量的增加而细化,低变形量时组织不均匀,变形量超过30%时能获得较好的细化组织;在1050~1130℃变形温度范围、以大于30%的较大变形量锻造时,晶粒度可以提高3个级别以上;采用大变形镦锻、反复镦拔可获得12级左右的再结晶组织,拉伸强度明显提高,断口特征为沿晶和穿晶混合断裂。

FGH96 is the second generation of power metallurgy superalloy in China,it is very difficult to forge and form by the conventional forging process.Therefore,in order to explore a reasonable preparation method for fine-grained disc billet,the hot die forging experiments were carried out at hot die temperature of 900℃with different strain rates,deformation temperatures and deformation amounts to study the change rules of microstructure for power metallurgy superalloy(P/M superalloy)FGH96.The results show that when the forging temperature is lower thanγ′phase solid solution temperature,the microstructure becomes more uniform with the increasing of the deformation temperature,and when the deformation temperature exceeds theγ′phase solution temperature,there is a tendency of grain growth.In addition,the grain sizes of alloy are refined with the increasing of the deformation amount,and the microstructure is not uniform when the deformation amount is low,but the better refined structure can be obtained when the deformation amount exceeds 30%.When forging with a large deformation amount greater than 30%at the deformation temperature range of 1050-1130℃,the grain sizes can be increased by more than three grades,and the recrystallization structure about grade 12 can be obtained by the large deformation upsetting and repeated upsetting and drawing,which significantly increases the tensile strength and presents the fracture characteristics of intergranular and transgranular mixed fracture.