Study On Fe-based Alloy Composite Coating For Repairing GCr15 Roll By Laser Cladding

In this paper,double-layer Fe-based alloy coatings with three kinds of powder were prepared on the GCr15 steel substrate by using synchronous powder feeding laser cladding process.The transition layer was LC alloy layer,and the surface layer was HC alloy layer,CeO₂/LC composite layer and NiCr-Cr₃C₂/LC composite layer respectively.The microstructure of cladding layer was analyzed by XRD,OM,SEM and EDS,and the microhardness and surface wear resistance of cladding layer were tested.The effects of laser process parameters,CeO₂ and NiCr-Cr₃C₂ powder content on the microstructure and mechanical properties of cladding layer were studied.The repairing and remanufacturing of the GCr15 cold roll surface will be achieved by obtaining the optimal coating system.The main phases of HC layers were?-Fe,Cr₇C₃ and?-Fe.The decreased thickness and width,gradually promoted surface smoothness of the cladding layer was observed with the increase of scanning speed.The refined microstructure,obviously improved microhardness and wear resistance of HC alloy layer were also obtained.The cross section hardness of LC/HC coatings decreased gradiently from surface to substrate.The fine microstructure,the high microhardness and the superior wear resistance were tested when the laser scanning speed was 130 mm/min.The main phases of?-Fe and Cr₇C₃ were detected in the CeO₂/LC composite coatings.The crack free but deteriorated surface formability were observed by adding CeO₂.The refined microstructure,increased microhardness and wear resistance of the coatings were acquired by adding 0.5%and 1.0%CeO₂,and that were opposite with 3.0%CeO₂ addition.The wear mechanism was mainly abrasive wear,and the highest microhardness and optimum wear resistance of the coatings were examined by adding 1.0%CeO₂.The main phases of?-Fe,Cr₇C₃,Cr₂₃C₆,Cr₃C₂ and?-Fe existed in the NiCr-Cr₃C₂/LC coatings.The arisen cracks and decreased microhardness of the coatings appeared by adding NiCr-Cr₃C₂.The gradually increased amount of?-Fe phase,refined microstructure,growing eutectic structure and elevated microhardness of the coatings were obtained with the increase amount of NiCr-Cr₃C₂ addition.The wear resistance of the coatings was gradually improved by adding 5.0%and 10.0%NiCr-Cr₃C₂,and which was decreased by adding 20.0%NiCr-Cr₃C₂.The main wear mechanism was abrasive wear,and oxidation wear occurred on the surface of coatings with 10.0%NiCr-Cr₃C₂ addition which possessed the best wear resistance.The microstructure and mechanical properties of three kinds of coatings were systematic examined.It was found that the LC/HC coatings had good forming effect and wear resistance,and met the needs of industrial production conditions of repairing GCr15cold roll.