Research On Microstructure And Properties Of Fe-based WC And High Nitrogen Steel Heterogeneous Component Deposited With Different WC Content Powder-cored Wires

In order to solve the problem of wire arc additive manufacturing high hardness additive structure,using plasma arc as fuse heat source,Fe-based WC powder-cored wire was introduced as hardening material and was used for a double wire addictive research with high nitrogen steel wire.The experimental study of the Fe-based WC powder-cored wire addictive bead,the study of the interlayer interweaving heterogeneous hardening and addictive structure and performance,and the analysis of the bead layer dislocation interweaving structure forming and tissue properties were mainly carried out.The effects of different WC particle content and different proportions of high nitrogen steel and Fe-based WC powder-cored wire on the microstructure,microhardness,tensile properties,impact properties and dynamic mechanical properties of the samples were studied,which provided a theoretical basis and engineering application reference for the integrated design and manufacture of heterogeneous high strength and high hardness additive structure and performance.Firstly,an experimental study was carried out on a single additive bead of Fe-based WC powder-cored wire to analyse the effect of WC particle content on the microstructure and mechanical properties of the enrichment bead,respectively.It was found that the tissues of the additive bead mainly consisted ofα-Fe,γ-Fe,Fe₃W₃C,unfused WC particles,M₇C₃ carbides and Fe₃C.As the WC content increased from 10%to 45%,the grain size of the additive bead gradually refined,the content of small angle grain boundaries changed from 14.47%to 71.92%,while the content of large angle grain boundaries changed from 85.53%to The CSL grain boundary content decreased from 14.14%to 4.7%.The mechanical properties tests showed that the average hardness of the bead increased from 348.96 HV_0.3 to 482.12 HV_0.3（38%increase）as the WC content increased,indicating that the increase in WC particle content created more carbides and small angular grain boundaries which increased the microhardness,but the reduction in large angular grain boundaries and CSL grain boundaries reduced the stability and crack resistance of the specimens.Next,the interlayer interwoven heterogeneous hardening structure of Fe-based WC powder-cored wire and high-nitrogen steel wire was investigated,using three filaments with10%,20%and 30%WC content with high-nitrogen steel.The transition zone was evident when Fe-based WC powder-cored was stacked onto the high-nitrogen steel,and the width of the transition zone varied from 64μm to 91μm as the WC content increased;there were a large number of M₂₃C₆ and M₇C₃ type composite carbides in the transition zone.The grain size near the transition zone is smaller than the grain size away from the transition zone,and the grain size gradually refines as the WC content increases.30%WC content specimens increase by more than 50 HV_0.5 in all areas compared to 10%WC specimens,with the Fe-based WC powder-cored area increasing by about 100 HV_0.5,indicating that the increase in WC content has a significant effect on the microhardness,but at the same time increases the increase in WC content has a significant effect on the microhardness,but at the same time increases the tendency of cracking.Finally,an innovative study on the forming and tissue properties of the Fe-based WC powder-cored wire-high-nitrogen steel wire bead interleaved structure was carried out.By optimising the path and program design,three scales of the bead interleaved structure were successfully prepared for the automated additive specimen,which formed well and had a reduced tendency to crack compared to the interleaved structure.The dynamic stress intensity of the specimens gradually increased with the reduction of the length of the short incremental bead of high nitrogen steel,reaching a maximum of 2071 MPa and 2167 MPa for the transverse and vertical specimens respectively,and the hardness of the Fe-based WC powder-cored wire region was in the range of 380-430 HV_0.5,indicating that the staggered interweave structure of the bead layers can ensure better mechanical properties while reducing the cracking tendency of the specimens.