Experimental Research On Influence Of Fluid Properties On Erosion-corrosion Of 35CrMo Steel

Erosion-corrosion of metallic materials is a phenomenon of surface mass loss caused by both physical wear and electrochemical corrosion.It happens in petroleum industry,chemical industry,water sector,electric power industry,metallurgy industry,etc.When the erosion-corrosion happens,it will result in loss of surface material,decrease of the wall thickness,perforation as well as rupture,and failure of equipment ultimately.In this paper,aiming at the corrosiveness of Cl~-and viscosity of experimental fluid,erosion-corrosion rules of 35 CrMo steel are experimented(tested)by self-made jet type experimental device and electrochemical testing system in solid-liquid two-phase flow,which is consisted of different concentration NaCl solution or hydroxypropyl guar solution and haydite.The experimental results are obtained by weight loss method and electrochemical method.Combined with electron scanning microscope,the effects of Cl~-concentration and the viscosity of the hydroxypropyl guar fluid on the erosion and electrochemical corrosion are discussed respectively.According to above researches,this paper draws the following main conclusions:(1)The effect of Cl~-concentration on the erosion-corrosion of 35 CrMo steel at low flow rate is mainly controlled by the effect of Cl~-concentration on the electrochemical corrosion.With the raise of Cl~-concentration,the erosion corrosion rate increases firstly,and then decreases.The erosion-corrosion rate reaches the maximum value of 348.70mm/a at the concentration of 3.5wt%NaCl solid-liquid two-phase flow.(2)When high-speed solid-liquid fluid flows,the erosion of 35 CrMo steel is the main factor of metal loss,which includes the pure erosion of the material and the incensement of the erosion caused by electrochemical corrosion.The pure erosion is a physical behavior,which has nothing to do with the change of Cl~-concentration,but the incensement of erosion caused by electrochemical corrosion is smaller,and it relates to Cl~-concentration a little.Therefore,the effect of Cl~-concentration on 35 CrMo steel at the high flow rate is small.(3)With the raise of the guar gum concentration,viscosity of fluid increases,which results in the ability carrying particles of fluid enhances,and the kinetic energy loss resulted from inter collision of particles decreases.Namely,the velocity of particle is more closed to flow rate of solid-liquid two-phase flow.Therefore,erosion-corrosion rate of 35 CrMo steel increases with the raise of fluid viscosity,and the erosion-corrosion rate reach the maximum value 46.56mm/a in 0.3% hydroxypropyl guar gum solid-liquid two-phase flow.