| As an acid-free surface descaling technology,abrasive water jet not only does not cause hydrogen embrittlement of materials,but also does not produce pickling waste liquid and waste gas pollution.It has great application prospects in the field of stainless steel descaling.However,the traditional abrasive water jet descaling uses garnet sand as the abrasive,which is seriously damaged during the abrasive water jet descaling process and is difficult to reuse,resulting in a higher cost of abrasive wear.Stainless steel shot has a high Owen life.As an abrasive,it can significantly reduce the comprehensive cost of abrasive water jet descaling and obtain higher descaling quality.In this paper,the erosion wear behavior of garnet sand and 410 stainless steel Shot on the surface of 2205 duplex stainless steel was studied,and the influence of abrasive particle size and working pressure on erosion wear mechanism was discussed.On this basis,further discuss the influence of abrasive particle size and working pressure on descaling effect and surface work hardening,and construct a clear functional relationship between abrasive particle size and working pressure and descaling width,surface roughness,jet strength and surface microhardness.In order to fully understand the microstructure strengthening mechanism caused by 410 stainless steel shot,the microstructure evolution of the surface layer of 2205 duplex stainless steel before and after descaling was studied.The microstructure strengthening mechanism and heterogeneous deformation induced strain hardening mechanism caused by abrasive water jet descaling were proposed,and the variation law of surface mechanical properties was discussed.Finally,the effects of stainless steel shot size and working pressure on residual stress strengthening and microstructure strengthening were studied.Combined with heterogeneous deformation induced stress,a new idea of uneven distribution of residual compressive stress in two phases was given,and the effect of isothermal annealing on work hardening was discussed.The erosion wear behavior of stainless steel shots and garnet sand on the surface of 2205 duplex stainless steel was studied.The results show that when stainless steel shots are used,the surface of 2205 duplex stainless steel can undergo stainless steel shot deformation wear and stainless steel shot ’piece’ wear.With the increase of particle size and working pressure of stainless steel shots,the deformation and wear efficiency of stainless steel shots is significantly improved.When the kinetic energy of stainless steel shots exceeds 3.49 × 10-4 J,stainless steel shots cause ’flake’ wear on the surface of 2205 duplex stainless steel.When using garnet sand,micro-cutting wear occurs on the surface of 2205 duplex stainless steel.At an impact angle of 80°,a ’pit’ shaped grooving is formed on the surface,and some garnet sand embedded materials cause surface pollution.The effects of abrasive particle size and working pressure on descaling quality and work hardening of 2205 duplex stainless steel were studied.The descaling width(32～48 mm),surface roughness(Ra:3.1～7.5 μm),abrasive water jet intensity(0.099～0.278 mmA)and surface microhardness(370～403 HV)produced by using garnet sand were higher than those produced by using stainless steel pellets(12～38 mm),surface roughness(Ra:0.9～3.8 μm),abrasive water jet intensity(0.066～0.245 mmA)and surface microhardness(356～396 HV).Because the influence of abrasive particle size on abrasive kinetic energy is more significant,the influence of stainless steel shot/garnet sand particle size on surface roughness and abrasive water jet intensity is higher than that of working pressure.The descaling width is affected by abrasive kinetic energy,jet shape and erosion wear mechanism.When stainless steel shot is used,the influence of particle size of stainless steel shot is higher than that of working pressure,but when garnet sand is used,the influence of working pressure is higher than that of garnet sand.The research on the microstructure evolution of the surface layer of 2205 duplex stainless steel before and after stainless steel shot descaling shows that when the stainless steel shot with a particle size of 0.4 mm is used to descale at a working pressure of 70 MPa,the plastic deformation of the ferrite in the surface layer of the sample depends on the dislocation movement,and the austenite is plastically deformed under the synergistic effect of dislocation movement,deformation twins and martensitic transformation.After descaling,about 10%of the austenite on the surface of the sample undergoes martensitic transformation,and the density of defects such as dislocations,grain boundaries,phase boundaries,and stacking faults is significantly increased.The austenite and ferrite are refined to varying degrees,and the residual compressive stress field is introduced.These changes increase the surface microhardness and yield strength of the descaling sample by 31.7%and 89%,respectively,forming a hardened layer with a depth of 550 μm.Since the strength of austenite is lower than that of ferrite,strain distribution occurs in austenite and ferrite during plastic deformation,and the geometrically necessary dislocations accumulated at the phase interface form directional heterogeneous deformation-induced stress,thereby generating additional heterogeneous deformation-induced strain hardening.The effects of stainless steel shot size and working pressure on the surface layer characteristics of 2205 duplex stainless steel were studied.The results show that with the increase of stainless steel shot size and working pressure,the maximum residual stress in austenite and ferrite is transferred from the surface to the subsurface.Because the strain hardening rate of austenite is higher than that of ferrite,the jet strength required for the maximum residual stress in austenite to appear on the subsurface is lower than that of ferrite.The direction of back stress in austenite is the same as that of residual compressive stress,and the direction of normal stress in ferrite is opposite to that of residual compressive stress.Therefore,the residual compressive stress in austenite of descaling sample surface layer is generally higher than that in ferrite.With the increase of particle size and working pressure of stainless steel shots,the martensite content and martensitic transformation depth,grain refinement and grain refinement depth,microhardness and hardened layer thickness in the surface layer are deepened to varying degrees.After isothermal annealing at 650℃ and 750℃ for 90 min,the surface microhardness of the descaling sample decreased by 11.1%and 18.0%,respectively,and the thickness of the hardened layer decreased to 100 μm and 250μm.According to the above research results,this paper expounds the erosion wear mechanism of stainless steel ball and garnet sand in abrasive water jet,and discusses the influence of abrasive particle size and working pressure on descaling quality and work hardening.By analyzing the surface microstructure evolution under the impact of stainless steel shots,the microstructure strengthening mechanism and heterogeneous deformation induced strain hardening mechanism of abrasive water jet descaling were clarified.The residual stress and microstructure of the surface layer under different descaling conditions were studied.The effects of particle size and working pressure of stainless steel shots on residual stress strengthening and microstructure strengthening were clarified.Combined with heterogeneous deformation induced stress,a new idea of uneven distribution of residual compressive stress in the two phases was given.The isothermal annealing experiment was used to discuss the heat treatment process to reduce work hardening.Through the above research,this paper provides theoretical support and technical support for the application of abrasive water jet using stainless steel shots in stainless steel descaling. |
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