Microstructure And Properties Of Ultra-high-speed Laser Cladding Of Cobalt-based High-tempe0ure Wear-resistant Coating On The Surface Of Cast Roll Sleeve

In the aluminum plate casting and rolling production,the casting roll sleeve is the main consumable.During service,the surface of the roller sleeve is subject to the interaction of high temperature and load,often due to premature wear pits,which affects the service life and the quality of the aluminum plate.Strengthening the surface of the roller sleeve and improving the high temperature friction and wear resistance of the surface of the roller sleeve is essential for improving the service life of the roller sleeve and stabilizing the quality of the cast-rolled aluminum plate.The emerging ultrahigh-speed laser cladding technology is very suitable for the rapid preparation of largearea laser alloyed layers on the surface of relatively large workpieces such as cast roll sleeves.In order to explore more efficient and new technologies for the surface strengthening of cast-rolling sleeves,cobalt-based alloy powder with excellent hightemperature performance is selected as the cladding material.The ultra-high-speed laser cladding technology and the relatively more mature conventional laser cladding technology were used to conduct process tests on the surface of the 32Cr3Mo1 V castrolling steel.Discuss the influence of process parameters on the performance of the cladding layer,optimize the cladding layer with the best performance,and compare and analyze the structure and performance of the cladding layer,and summarize the influence of the cladding layer structure and element distribution rules on the performance.The results show that the preferred ultra-high-speed and conventional laser cladding layers have a smooth surface and a good combination with the substrate,without obvious defects such as cracks and pores.In contrast,the ultra-high-speed laser cladding layer has lower surface roughness and smaller heat-affected zone thickness.The microstructure of the ultra-high-speed laser cladding layer is very uniform and fine,and the dendrite axis spacing is extremely small,which largely suppresses the range of dendrite segregation,makes the element distribution of the cladding layer more uniform,and the difference in element content between dendrite and dendrite is smaller.At the same time,the cladding layer has obvious arching and delamination.The bottom and middle areas of the cladding layer are mostly columnar crystal structures with highly consistent growth directions.There is a slight grain coarsening in the fusion line area,and the growth direction of the dendrites in the top area of the cladding layer is relatively disordered.The microstructure of the conventional laser cladding layer is relatively coarse and disordered,the average distance between crystal axes is larger,and the element segregation between dendrites is more obvious.In the ultra-high-speed laser cladding process,the extremely low heat input and the ultrahigh overlap rate make the melting of the substrate extremely low,and the cladding layer is less diluted by the substrate.The phase composition of the two preferred cladding layers has little difference,and both are composed of ?-Co and Co,Cr,and W carbides.At the same time,the ultra-high-speed laser cladding layer has significantly higher microhardness.In the 700? high temperature friction and wear test,the wear amount of the two cladding layers is much lower than that of the matrix.Among them,the oxide wear debris produced by the ultra-high-speed laser cladding layer is smaller,and the agglomeration effect is more likely to occur,which is conducive to the formation of the compacted oxide layer;The amount of deformation is smaller,which effectively supports the compacted oxide layer,which is beneficial to the maintenance of the compacted oxide layer.A large area of compacted oxide layer with anti-friction and wear-resisting effect appears,showing excellent high-temperature friction and wear resistance.The conventional laser cladding layer has a large deformation and cannot effectively support the compacted oxide layer.At the same time,large oxide wear debris is generated,and the formation and maintenance of the compacted oxide layer are inhibited.