含预置板的双层钛合金超塑成形/扩散连接零件缺陷分析及工艺改进

Defects analysis and process improvement for double-layer SPF/DB structure parts of titanium alloy with pre-set panel

采用超塑成形/扩散连接(SPF/DB)工艺成形了含预置板的TC4钛合金双层结构零件,试验发现成形缺陷主要包括两类:外观缺陷和内部缺陷。外观缺陷包括表面沟槽、表面阶差、表面凹坑和气道塌陷等,内部缺陷包括焊合率低和预置板定位偏移等。通过对各缺陷的分析和对多层板SPF/DB技术关键点的梳理,深入剖析了缺陷形成的主要原因:止焊剂和毛料等定位偏差、成形模具和气道间隙尺寸偏差、止焊剂涂覆质量不良和表面准备状态不佳等。提出了消除缺陷的工艺措施,包括提升止焊剂涂覆工艺、改善成形模具结构设计、提高模具制造精度和改进定位协调方式等。试验结果证实这些措施能够有效避免各类缺陷的出现,达到零件各项技术指标。

Double-layer structure parts of TC4 titanium alloy with pre-set panel was fabricated by superplastic forming/diffusion bonding(SPF/DB)process.It is found by the experiments that the forming defects mainly consist of two types:appearance defects and internal defects.The appearance defects include surface groove,gradient step,pit and airway collapse,etc.The internal defects include low welding rate and position deviation of the pre-set panel,etc.By analyzing these defects and combing the key points of SPF/DB technology for multi-layer sheet,the main causes of the defects were deeply analyzed,including the position deviation of the welding blocking flux and the blank,the size deviation of forming die and air passage,the poor coating of welding blocking flux and the bad surface state,etc.The technological solutions for eliminating defects were proposed,including improving the coating process of welding blocking flux,optimizing the structure design of the forming die,increasing the precision of die manufacturing and improving the coordinated methods of positioning.The experimental results verify that the defects can be effectively avoided by these solutions to achieve the technical indexes of parts.