| Rolls are important parts of rolling production, the use performance of it’s surfacedirectly affects the service life of rolls. The iron-based, nickel-based alloys and hard alloymaterials have been widely used In laser surface alloying of rolls. Currently there are stillsome problems in material selection of laser surface alloying of rolls: The main problem isthat the kind of materials is limit. There are no specific designed materials for laseralloying, and current materials can not meet the use performance of rolls in the situation ofhigh temperature, spalling and cracking of the alloy layer are always serious. These havegreatly influenced the development of laser surface alloying technology of rolls. Therefore,it is very important to design useful materials for laser surface alloying of roller.A new cobalt-based super alloy powder material is designed in this paper. Co isselected as the main element in this powder material, and WC, Cr3C2, Cr, Mo, Si, B, Ni.micro-nano particles are added according to solid solution strengthening, dispersionstrengthening and grain boundary strengthening. The harmful phases are controlledthrough phase calculation theory, the average electron density of each powder formulationare controlled in a reasonable range In order to further adjust the powder ingredients. Thebest powder formulation is selected through subsequent laboratory analysis and namedCo-Cr3.Analysis of the microstructure of alloy layer show that there were three sections withdifferent microstructure from surface to the centre: the melting zone, the heat-affected zone,the base zone. Organization of melting section is the typical dendritic structure withdirectional characteristic and Compact distribution. The organization of heat-affected zoneinclude a small amount of spherical graphite and martensitic.the organization of thedendrites through EDS and XRD analysis are various carbides, including（Cr，Fe）7C3，（Cr，Fe）23C6.The organization between dendrites are composed of small ledeburite and austenite. The Co, Ni, Cr and other elements in eutectic austenite add the effect of solidsolution strengthening.The micro hardness test showed that the average traverse micro hardness of theCo-Cr3alloy layer is711.7HV0.5while the average longitudinal micro hardness is707.9HV0.5. Which is twice larger than the hardness of ductile iron, and there is nohardness mutation in the alloy layer. Significantly improved the hardness of the rolls.Further analysis, distribution of hardness of the alloyed layer is consistent with itsorganizational structure distribution. Although the hardness decreased in the lap sections.but the decrease is slightly, and the overall hardness of the coating remain high.The analysis of friction and wear test of Co-Cr3alloyed layer at room temperature,480℃and800℃showed that the corresponding average coefficient of friction of thealloyed layer were0.345,0.342and0.259.The alloyed layer had the smallest and moststable friction coefficient at800℃. The volume loss of ductile iron and boron carbidecoating were7.56and3.54times more than Co-Cr3alloyed layer, the Co-Cr3alloyedlayer had the best wear resistance.Remarkable effects had been achieved since the using of Co-Cr3superalloy powder inlaser surface alloying of rolls: the one was the Increasing of the rolling amount of singleslot, the average rolling amount of single slot was more than doubled compared to boroncarbide alloy; another was the improving of efficiency of the rolling mills, the wearresistance and the service life of rolls had been improved by using Co-Cr3superalloypowder. Significantly reduced the times of the replacement of rolls and improved theproduction efficiency. It also further validated the reasonable of the experimental processand powder formulations. |
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