Research On Ceramic Phase Reinforced Fe-based Coating By Laser Cladding On High Chromium Cast Steel Surface

Roll as a major part of rolling mill, has been widely using in the metallurgical industry. In the steel rolling process, the surfaces of roll usually suffer from normal abrasion and crack after a procedure of service, due to the presence of severe wear of the friction between the roll and the steel material,which seriously affects the quality of the rolled product. The advantages of laser cladding technique and metal-ceramic composite coating in situ synthesized, situ synthesis of ceramic matrix composite reinforced Fe-based coating by laser cladding technology on surface of roll. Micro-hardness tester, optical microscope, scanning electron microscopy (SEM), X-ray diffraction (XRD), sliding wear testing machine and box-type resistance furnace are used to test and analyze the microstructure and properties of laser cladding.In this paper, the influences of positive defocus, line energy, thickness of preplaced powder and overlapping ratio of multi-pass layers on the surface morphology, geometry, dilution rate and performance of the cladding layer. The results show that, a Fe-based cladding layer with good surface roughness, good metallurgical bonding with the substrate and without cracks, inclusions, porosity and other defects can be obtained under1000W laser power,5mm/s scan velocity,15mm positive defocus,thickness of preplaced powder of about0.8mm,shielding gas flow rate of15L/min, and overlap rate of30%.The influence of organization and the performance of the different vanadium, boron atomic ratio of the alloy powder are researched. VB particles with blocky and strip shape are distributed uniformly in the clad layer. The coatings with better cracking resistance can be obtained when the atomic ratio of V to B in the preplaced powder is between1:1. With the increase of boron iron, surface roughness of the cladding layer becomes worse, the hardness is gradually increased. In addition to VB, iron boron compounds also appeared cladding layer, these iron-boron compounds increase the hardness of the cladding layer and also increases the tendency to crack the cladding layer, resulting cracks appear cladding layer.The influence of organization and the performance of the different vanadium iron and B4C ratio of the alloy powder are researched. VB particles with blocky and strip shape and VC with snowflake-shaped are distributed uniformly in the cladding layer. The coatings with better forming, higher hardness can be obtained when the atomic ratio of V to (B,C) in the preplaced powder is between1:1.2, the average hardness is1023HV0.3. The wear resistance of the cladding layer is about4-5times that of base metal. The main wear mechanism of base metal is adhesive wear and abrasive wear, but wear mechanism of the cladding layer is mainly adhesive wear.The influence of organization and the performance of the different addition of molybdenum iron on VC-VB cladding are researched. High quality cladding layer can be get when vanadium iron-B4C-molybdenum iron (86.73-9.10-4.17wt.%) is selected as a cladding alloy powder. The average hardness of the cladding layer is1153HV0.3,because in situ synthesized VB-VC-MoC phase is uniformly dispersed in enhanced matrix and Mo is dissolved in the cladding layer. The wear resistance of the cladding layer is about9times that of base metal. Wear surface is not obvious furrows, peeling pits are small and thin. The oxidation resistance at600℃of the cladding layer is5times that of the cladding layer without Mo, and twice that of the base metal.