Research On Cracks Repairing Technology Of TC4 Alloy Spoke Type Casing

The spoke plate casing is an important component in the aero engine.It consists of the inner ring,the outer casing and the fixed support plate,which is made of TC4 titanium alloy.When the aero engine running cycle is completed,the crack failure of the support plate reaches up to 30%,the crack failure of the outer casing body reaches up to 10%,and it must be repaired in order to continue using.In this paper,the crack defect repair process of the outer ring base body and the support plate of the titanium alloy spoke plate casing was studied.According to the crack shape and the location of the casing crack,the sample performance tests such as plasma arc welding,electron beam welding and post-weld heat treatment and shot peening were carried out,and the repair process was verified on the test piece.TC4 alloy forging specimens with the thickness of 2mm(equivalent to the thickness of the main body of the casing)were used as test materials,butt electron beam welding was conducted,and the vacuum heat treatment after welding to eliminate the stress and the shot peening technology on the welding surface were studied.After vacuum electron beam welding and vacuum heat treatment at 600℃ +2h after vacuum welding together with shot peening at the welding surface,tensile strength at room temperature and tensile strength at high temperature were higher than the standard value,the elongation rate was more than 10%,high temperature lasting strength reached the standard requirements,no welding specimen fracture occurred.The 1.2mm TC4 plates were taken as the test material for butt single-layer plasma arc welding.After welding,the process research on filled argon protecting partial heat treatment to eliminate stress and welding surface polishing was carried out.In normal environment,the specimens were welded by plasma arc welding,after welding the heat treatment with argon protection was taken in the condition of 600℃ +1.5h,and then the welding surfaces were polished.The microstructure analysis showed that the welded joints were well organized,the tensile strength at room temperature and tensile strength at high temperature were higher than the standard value,and the elongation rate was more than 10%,all welding specimens were broken off in the base body;high temperature durable strength reached 540 MPa / 100 h,welding specimens did not fracture.Based on the above experimental results and practical engineering applications,the process research on removal scheme,the repair method and the deformation control method that was used for spoke plate casing base body and support plate with crack damage was carried out.The electron beam welding and plasma arc welding repair process were applied to repair the cracks in the spoke plate casing base body and support plate successfully.The repaired titanium alloy casing meeted the requirements of overhaul engine.The technological achievement has filled the domestic gap of crack repair technology for titanium alloy spoke plate casing.The engineering application effect is good,as of August 2017 about 30 sets of spoke plate casings have been repaired and installed.The technology has reduced the cost of replacing new parts of the overhaul engine,and achieved greater economic benefits.