High-entropy Welding Of 304/Q235 Stainless Steel Clad Plate

304/Q235 stainless steel clad plate not only has the best qualities of both stainless steel and carbon steel,but it also saves the most resources and expenses without compromising the use impact.It has a lot of potential in the petrochemical industry.Welding is an important connection method for stainless steel clad plate engineering applications,and the quality of welding play a decisive role in the performance and life of the product.However,the diffusion and convection of elements will occur during welding of 304/Q235 stainless steel clad plates,which will reduce the corrosion resistance of the cladding weld,embrittlement caused by the formation of martensite at the interface,and weld softening caused by decarburization of the base weld.The high strength,high toughness and excellent corrosion resistance of high-entropy alloys are exactly what are needed for welded joints.Therefore,in this paper,multi-principal material was used as the weld filler materials,and it was expected to realize the high-entropy connection of the welded joint of 304/Q235 stainless steel clad plate,thereby improving the service performance of the welded joint.First,Fe Co Cr Ni Mn powder,Cr Ni₂Mn Ti_0.5Al_0.5 multi-principal mixed powder and Fe-based materials were used as filler materials,to explore the feasibility of welding 304/Q235stainless steel clad plates with multi-principal material as a single filler for welds,and the effects of different fillers on the microstructure and properties of welded joints were explored.The study found that the three types of welded joints were all columnar grains grown near the base metal/weld interface in the weld zone（WZ）,however,which were all equiaxed grains in the weld center.The phase structure of the weld zone was different:the Cr Ni₂Mn Ti_0.5Al_0.5 sample was FCC+Ti-Al dual-phase structure,the Fe Co Cr Ni Mn sample was single FCC phase structure,and the Fe-based filler materials sample was single BCC phase structure.As a result,the Cr Ni₂Mn Ti_0.5Al_0.5 specimen had a tensile strength（～526 MPa）about that of the base metal（BM）,the Fe Co Cr Ni Mn specimen had the largest elongation at break（～79%）,and the Fe-based filler materials specimen has the lowest elongation at fracture,only was～50%,but the tensile specimens all fractured in the base metal near the heat-affected zone,which confirmed to the needs of engineering application.In addition,two high-entropy welded joints provided superior corrosion resistance for the clad base metal 304 stainless steel.The Cr Ni₂Mn Ti_0.5Al_0.5 sample and the Fe Co Cr Ni Mn sample were heat-treated under the conditions of 800°C and held for 4 h to explore the effect of post-weld heat-treatment on the microstructure,phase and joint properties of the weld.After post-weld heat-treatment,it was found that the Ti-Al phase of the Cr Ni₂Mn Ti_0.5Al_0.5 sample was dissolved in the weld area to produce lattice distortion,and a new BCC phase appeared in the weld area,resulting in an increase of about 82%in the microhardness of the weld area,the plasticity decreased by about72%,and the strength of the welded joint decreased by about 146 MPa.Furthermore,the decrease of Cr element in weld zone lead to the increase of corrosion rate about 3 times after heat-treatment.However,the phase structure of the Fe Co Cr Ni Mn sample in the weld zone did not change significantly,but the grains became coarser,resulting in a slight decrease in the hardness,yield strength and corrosion resistance of the weld zone.Controlling the structure and properties of high-entropy alloys can be achieved by changing the types and contents of components.Herein,the effect of element content on the microstructure of the weld and joint properties was explored by changing the number of Al wires in the filler materials.The study found that high-entropy welding of 304/Q235 stainless steel clad plate could be achieved by using Cr-Ni-Cu-Al multi-principal alloy wire as filler materials through TIG welding wire by feeding wire.When the Al content was 10 at.%,the weld had a single FCC phase structure,and the grains were columnar and equiaxed dendrites.As the Al content increased to 19 at.%,the phase structure of the weld zone did not change significantly,but the grains were transformed from columnar crystals and equiaxed dendrites to cellular crystals.When the Al content reached 26 at.%,the weld zone presented a dual-phase structure of FCC+BCC,and the grains change from cellular crystals to amplitude-modulated decomposed structures,the microhardness and tensile strength of weld zone increased with the increase of Al content.However,with the increase of Al content,the corrosion resistance of the weld zone decreased continuously,and the corrosion rate increased from 0.08 mm/a to 0.10mm/a,and finally to 0.15 mm/a,but all are lower than 0.17 mm/a of 304 stainless steel.