Study Of Ferrous Alloy Prepared By Laser Cladding On The Surface Of Cr5 Backup Roll And Their Structure Property

Backup roll is a large shaft type of roller used to support working roll in four roll and multi-roll mill,so it can effectively reduce the diameter of working rolls and increase the rigidity of working rolls.Because in the process of backup roll contacting with working roll,backup roll continuously bears huge alternating load,and the surface of the body wear and strain-hardening,so the failure modes of backup roll are mainly wear and spalling.Because of the large volume and the expensive cost of the backup roll,to prolong the service life of the backup roll is very crucial for improving the economic benefits of the steel mills through the surface strengthening and repair.Laser cladding technology is a kind of rapid prototyping technology which can prepare into dense and metallurgical bonding between coating and substrate,so that the surface property is improved,compared with the traditional surface technology has obvious advantages.However,the type of special powder of laser cladding is limited,the hardness of the cladding layer prepared by thermal spraying powder is difficult to control,and the property is difficult to meet the requirements of the backup roller.This article aims to adjust components of the F313 iron-based powder,and use laser cladding on the surface of backup roll to prepare the coating which is metallurgical bonding,dense in microstructure,less defect,matching to hardness of the working roll and wear-resistant.To provide a new way that is using laser cladding with thermal spraying with iron based powder to strengthen and repair the backup roll.Taking Cr5 steel backup roller as the subject,explore the feasibility of applying semiconductor laser to prepare of coating on the surface.Through laser process parameters optimization,the adjustment of the powder composition,prepare a coating that is reasonable hardness and excellent performance.By means of optical microscope(OM),the supplementary energy spectrometer(EDS),scanning electron microscope(SEM),X-ray diffraction(XRD),micro-hardness tester and high temperature friction wear tester and so on,the preparation of coating on the microstructure,composition,phase composition,hardness and wear behavior were studied.Process parameters of F313 powder using semiconductor laser cladding are as follows:laser power is 1600 w,scanning speed is 8 mm/s,defocusing distance is 10 mm,feeding rate is 14.7 g/min,overlap rate is 30%.The microstructure of laser cladding coating was compact,metallurgical bond with the substrate,has less defect.The average hardness of the cladding layer is about 650 HV,higher than most of maximum hardness requirements of the backup roll.By increasing the iron content in F313 powder and add the nickel element into F313 powder,the two kinds of methods were employed to adjust the compositions,to control the hardness of the cladding layer.To adding different content of iron powder,the hardness of cladding layer can be controlled in the range from 490 HV to 620 HV;To add different nickel powder,the hardness of cladding layer can be controlled in the range from 420 HV to 610 HV.According to the current most commonly used Cr5 steel backup roll hardness requirements,choose two components of powder are carried out wear resistance tests of cladding layer,the main wear way of cladding layer is abrasive wear.After 30 minutes of wearing,the loss in the mass of two cladding layers is less than 50%of the Cr5 steel substrate.