Machined Surface Integrity By Mechanical Milling/Heat Treatment Combined Processing Superalloy GH4169

Superalloy GH4169 parts are manufactured through a series of processes,including machining and heat treatment.However,GH4169 is difficult to machine due to its work hardening and generated residual stress during machining.The severe work hardening is disadvantageous to continuous cutting of superalloy.The residual stress will deteriorate the shape accuracy of the machined parts.The mechanical properties evolution of machined superalloy GH4169 surface is the researched in this thesis.The milling and heat treatment combination process is carried out.The mechanical properties and microstructure of machined GH4169 are evaluated and analyzed.The influences of milling and heat treatment combination process on work hardening,residual stress and microstructure are discussed.Firstly,the mechanical properties of machined surface for milling GH4169 are characterized.The difference of residual stress between cutting direction and feed direction and the maximum work hardening degree on GH4169 machined surface are analyzed.The effects of milling speed and feed per tooth on the work hardening and residual stress are presented.The relationship between mechanical properties and milling parameters is revealed.Secondly,the microstructure and microhardness of heat-treated GH4169 surface are analyzed.The phase composition of GH4169 after solution and aging treatment is measured by XRD technology.The grain size and microhardness of GH4169 after solution heat treatment are analyzed.The effect of heat treatment on the microstructure of GH4169 is presented.The relationship between grain size and microhardness is proposed.Thirdly,the effects of milling/heat treatment combination processing on the microstructure and microhardness of GH4169 machined surface are researched.The GH4169 surface microstructure processed by combined milling/heat treatment process is characterized.The plastic deformation,grain refinement and work hardening degree of GH4169 surface machined by the solution heat treatment and milling combination processing are analyzed.Effect of this combination processing sequence on work hardening and microstructure of GH4169 is revealed.Finally,the workpiece deformation caused by residual stress on GH4169 machined surface is researched.The residual stress relaxation mechanism due to dislocation slip and precipitation of strengthening phase on GH4169 machined surface processed by milling and annealing is presented.The workpiece GH4169 deformation caused by residual stress is analyzed.The bending deformation of GH4169 workpiece caused by residual stress on machined surface is modelled and predicted and the GH4169 annealing process is formulated.