High-temperature Wear Performance of NiCrCoBSi Multiple Principal Elements Alloy Coating Sprayed by HVOF on the Surface of Crystallizer Copper Plate
Crystallizers are the core components of continuous casting equipment,and their quality directly impacts billet quality and production efficiency.With the advancement of high-drawing-speed continuous casting technology,higher performance requirements for crystallizers have been proposed,particularly concerning wear,a major cause of crystallizer copper plate failure.Currently,electroplated crystallizer coatings hold approximately 80％of the market share.However,the long deposition cycle,low hardness,tendency for coating peeling,and environmental pollution caused by electroplating technology make it inevitable for this technology to be phased out.Supersonic flame spraying(HVOF)is one of the most widely used thermal spraying technologies,capable of producing highly dense and uniform coatings due to its fast flame flow rate,high powder kinetic energy,and low oxidation levels.In addition,the HVOF technology offers a wide range of material options and can be functionally designed to accommodate different sizes and parts of the crystallizer,meeting continuous casting requirements.A NiCrCoBSi multiple principal element alloy coating has been applied to the surface of crystallizer copper plates using HVOF technology to improve their high-temperature wear performance of copper plates.The microstructure of the NiCrCoBSi coating was studied using X-ray diffraction,scanning electron microscopy,and transmission electron microscopy.The wear resistance of the coatings was evaluated using frictional wear equipment and compared with that of the commonly marketed electroplated NiCo coating.Additionally,the wear mechanisms of the coatings were analyzed.The results showed that the NiCo coating had a single-phase face-centered cubic solid solution structure,whereas the NiCrCoBSi coating exhibited an FCC solid solution,with CrB and M23C6 as the main phases.Both coatings had high densities with no observed cracks.A clear delamination was found between the NiCo coating and the copper alloy substrate,with no transition zone,indicating a mechanical bond.In contrast,a diffusion layer between the NiCrCoBSi coating and the copper alloy substrate due to diffusion heat treatment after spraying,resulting in the formation of a metallurgical bond.Compared to NiCo coating,NiCrCoBSi coating exhibited a 95％increase in hardness,whereas the fracture toughness decreased by only 5.4％.The friction factor of the NiCo coating fluctuated significantly,ranging from 0.4 to 1.0,and eventually stabilizing around 0.6.Compared with the NiCo coating(0.67),the friction factor of NiCrCoBSi coating is lower(0.51),with the curve showing good stability,ranging from 0.4 to 0.6,and ultimately stabilizing at around 0.52.After wear,the surface of the NiCo coating exhibited large flakes accompanied by dark gray adhesive marks,cracks,and debris.The wom surface of the NiCrCoBSi coating showed signs of debris,peeling,furrowing,and adhesive wear,with many small peeling pits.The wear mechanisms of both coatings were adhesive and fatigue wear,accompanied by a small amount of abrasive wear.The wear rate of NiCrCoBSi coating was 1.53×10-5 mm·N-1·m-1,which is about five times higher than that ofNiCo coating(7.91 × 10-5 mm·N-1·m-1).The main reasons for the higher wear resistance of the NiCrCoBSi coating are the better hardness,various wear-resistant phases,and the work hardening of the wear surface layer.This hardening occurs due to the plastic deformation of the coating under cyclic loading,during which the hard phases of the coating were cut and rotated.The carbides and borides are refined and spheroidized,enhancing the hardness of the wear surface layer.This research paves the way for developing coatings with excellent wear resistance for copper and their alloys.
high-velocity oxygen fuelmultiple principal elements alloyscopper platecoatingwear
万方数据
维普
