Study On High Entropy Alloy Coating For Cast Iron By Laser Cladding

The traditional alloy design concept is that the more alloying elements,the more likely intermetallic compounds will form and the performance of the alloy become worse.The concept of high entropy alloy is an innovation and breakthrough of traditional alloy design and development.Due to the multi-principal element effect,the high-entropy alloy inhibits the generation of intermetallic compounds and mainly forms a simple solid solution structure,which often has the advantages of high hardness,good toughness and excellent wear resistance.In this paper,the gray cast iron HT250 of wide application and low cost is selected as the substrate material to prepare the high-entropy alloy coating on its surface,which not only improves the surface properties of the substrate gray cast iron,but also expands the application range of the laser cladding high-entropy alloy coating,and has certain industrial application value.In this paper,Al,Co,Cr,Ni,Ti mixed metal powders were preset on the surface of gray cast iron HT250,and laser treatment was carried out with YLS-5000 fiber laser to prepare high-entropy alloy coating on the surface of gray cast iron.Microstructure,phase composition,microhardness,wear resistance and high temperature softening ability were studied by optical metalloscope(OM),X-ray diffractometer(XRD),scanning electron microscope(SEM),energy spectrum analyzer(EDS),microhardness tester,friction and wear test and annealing treatment.The experimental results showed that Al Co Cr Fe Ni Ti high-entropy alloy coating was successfully prepared with laser power of 2500 W,scanning speed of 9mm/s and spot diameter of 5mm.The coating formed well without obvious defects and was combined with the substrate by realizing metallurgy.The coating structure is mainly composed of BCC solid solution phase,including some FCC solid solution phase and Ti C phase,which are dispersed and distributed in the coating structure.Microhardness test results showed that the average hardness of the high-entropy alloy coating was about 600 HV,which was three times of the hardness of the substrate.Laser cladding coating of high-entropy alloysignificantly improved the hardness of the substrate surface.Friction and wear test results show that: under the same condition of the friction and wear,to compare high entropy coating and substrate,mass loss from 678.15 mg to 13.25 mg,trail width from 1.48 mm to0.62 mm,friction coefficient from 0.61 to 0.28.The substrate wear morphology showed obvious furrow and spalling,the coating wear mode was mainly adhesive wear,the wear mark surface was relatively flat,and the coating wear resistance was significantly improved.After 900 ? high temperature annealing treatment,high entropy alloys coating microhardness is remained,has a good resistance to high temperature softening performance.