Microstructure And Properties Of Ultrasonic Assisted Laser Cladding TiC Reinforced CrMnFeCoNi High Entropy Alloy Coating

Laser cladding CrMnFeCoNi high entropy alloy coatings are widely used in the surface repair and strengthening of key and vulnerable parts in the industrial field.However,with the improvement of the comprehensive strength in related fields,the requirements for the strength,wear resistance and corrosion resistance of coatings are getting higher and higher.In this study,TiC reinforced CrMnFeCoNi coatings were prepared by ultrasonic assisted laser cladding to improve the hardness,wear resistance and corrosion resistance of high entropy alloy coatings.The details are as follows:(1)Process optimization of laser cladding CrMnFeCoNi coatings.Based on the control variable method,the CrMnFeCoNi cladding layer with different process parameters was prepared by laser cladding method.The macroscopic morphology,microstructure,microhardness,wear resistance and corrosion resistance were analyzed,and the corresponding relationship between the coating microstructure and properties and the laser cladding process parameters was obtained.The results show that the cladding layer prepared with 1000 W laser power and 6 mm/s scanning rate has good forming quality,good wear resistance and corrosion resistance.(2)Microstructure and properties of laser cladding TiC/CrMnFeCoNi coatings.When the content of TiC was 2 wt.% and 4 wt.%,the TiC phase appeared as the second phase with different shapes(stripe,round,square and petal-shaped)in the matrix.When the TiC content increases to 7 wt.%,the TiC phase begins to fuse obviously,and the fusion degree of TiC phase intensifies with the continuous increase of TiC content;the friction coefficient and wear amount of the cladding layer decreases first and then increases.The main reason is that in the cladding layer with high TiC content,the uneven distribution of the strengthening phase TiC leads to the local existence of easyto-wear areas,which inhibits the improvement of wear resistance.The corrosion resistance of the cladding decreases significantly with the introduction of TiC phase,but increases significantly with the increase of TiC content.The corrosion resistance of the cladding layer with 10 wt.% TiC content is almost close to that of the cladding layer without TiC.(3)Effect of ultrasonic vibration on microstructure and properties of laser cladding TiC/CrMnFeCoNi coatings.(1)Effects of different ultrasonic amplitudes on the microstructure and properties of coatings with 4 wt.% TiC content: with the introduction of ultrasound and the enhancement of ultrasonic amplitude,the lattice constant corresponding to the base phase of high entropy alloy gradually increases,which is related to the lattice distortion of the base phase caused by TiC solid solution;The TiC phase accumulated in the coating is gradually dispersed,spread laterally along the dendritic grain boundary and extended into the crystal,covering the whole test area in a network,which can effectively improve the wear resistance of the cladding layer;The corrosion resistance of the coating increases first and then decreases significantly.The decrease of corrosion resistance is related to intergranular corrosion.(2)Effect of10 μm ultrasonic amplitude on microstructure and properties of coatings with different TiC content: with the introduction of ultrasonic,the distribution characteristics and growth morphology of TiC in different coatings are different.The TiC phase in 2 wt.%TiC coating spreads horizontally along the branch grain boundary,the spreading degree and range of TiC phase in 4 wt.% TiC fusion coating increase along the branch grain boundary,some TiC phases are interconnected in fishbone shape,and some TiC phases in 10 wt.% TiC coating still show certain block agglomeration;The wear resistance of coatings with different TiC content is significantly enhanced,but some areas of 10wt%TiC coating still have adhesion and falling off,which is mainly due to the failure to fully spread the high content TiC phase under the action of ultrasound,resulting in the reduction of the coverage area of the strengthened phase to a certain extent.The corrosion rate of 10 wt.% TiC coating is still low,mainly because some TiC phases still show a certain degree of block polymerization,which can avoid intergranular corrosion and play a good role in corrosion resistance.