Optimization Of Welding Parameters And Study On Corrosion Resistance Of TA10/Q345 Composite Plate

TA10/Q345 composite plate not only has excel ent corrosion resistance of titanium al oy,but also has high strength of steel.It is widely used in petrochemical industry,marine engineering,aerospace and other fields.The adaptability of the TA10/Q345 composite plate for welding and the aggressive media in the environment can affect its service life.In this paper,combined with TIG welding and laser arc hybrid welding methods,the TA10/Q345 composite plate is divided into three parts:base layer,transition layer and cladding layer.The influence of welding parameters on the microstructure of the weld is explored.At the same time,combined with electrochemical experiments,the corrosion resistance behavior and mechanism of TA10and welded joints in artificial seawater medium were studied.The base weld structure consists of a large amount of ferrite and a small amount of pearlite.The ferrite is massive pro-eutectoid ferrite and fine acicular ferrite.The pro-eutectoid ferrite has obvious directionality and a certain angle with the fusion line.Coarse grains,a large amount of pro-eutectoid ferrite and acicular ferrite increase the hardness of the weld.Its microhardness value is 280HV0.2-320HV0.2.From the fusion line to the center of the weld,the transition layer structure consisits of planar crystal,cell crystal,dendritic and equiaxed crystal.The chemical composition of the bright gray area in the weld is Cu-52.35%,Fe-16.86%,Ti-30.79%.The possible phase composition is Ti Cu₂+Ti₂Cu₃+Fe(s,s).The chemical composition of the dark gray area is Fe-46.92%,Cu-10.3%,Ti-41.78%.The possible phase composition is Ti Cu+Ti Fe₂.The cladding weld is divided into two areas,an arc zone and a laser zone.The arc zone consisits of a coarse band-like structure that grows perpendicular to the wall of the molten pool toward the center.The laser zone near the wall of the bath consists of columnar crystal and the central region consisits of fine equiaxed crystal.The heat-affected zone has basket-like structure in which the Wei's tissue and the?'-needle are staggered.The coarse columnar crystals and a large amount of acicular martensite make the weld microhardness as high as 460HV_0.2-530HV_0.2.There are micro-cracks and pores in the center of the weld and at the interface between the transition layer and the cladding layer.The content of Ti and Fe near the crack is high.Ti-Fe brittle compound is formed,which leads to crack initiation.The pores are mainly circular or elliptical and distributed in the vicinity of the interface between the cladding and the transition layer in the laser region,and the size ranges from 50?m to 100?m.The dynamic potential polarization curve of base metal TA10 is similar to that of welded joint,and its anodic polarization curve can be divided into three stages:active dissolution zone,passivation zone and overpass zone.When the polarization potential increases from 0.3V to0.9V,the charge transfer resistance of the passivation film increases,the electric double layer capacitance decreases,the film resistance increases,the capacitance decreases,the number of defects decreases,the integrity increases,and the corrosion resistance increases.When the polarization potential increases from 0.9V to 1.1V,the electric double layer capacitance increases,the film resistance decreases,the capacitance increases,the number of passivatio n film defects increases,the denseness decreases,and the corrosion resistance decreases.The welded joints have a higher corrosion rate than the base metal,but still have good corrosion resistance.