Abstract:The purpose of the present research is to analyze the phase composition,defect substructure and Hardox 450 steel microhardness after surfacing with powder-cored wires of different chemical composition.Hardox 450 steel with a n minal strength of 1250 MPa was used in the present study.The main alloying elements were:C=0.22％,Mn=1.05％,Si=0.23％,Ni=0.05％,Cr=0.89％,Mo=0.01％,V=0.02％,P=0.007％,S=0.002％.For the study the iron-base wires of the following compositions were chosen:No 1(С-Mn-Ni-B wire):C=0.7％,Mn=2.0％,Ni=2.0％,B=4.5％;No 2(C-Mn-Si-Cr-Nb-W wire):C=1.3％,Mn=0.9％,Si=1.1％,Cr=7.0％,Nb=8.5％,W=1.4％;No 3(C-V-Cr-Nb-W wire):C=1.4％,V=1.0％,Cr=7.0％,Nb=8.0％,W=1.2％,they are the most often used in surfacing for increasing the mechanical properties of surface.The welding parameters employed were:current=250 A,voltage=28 V and speed 6.5 m/min.A shielding gas used in mIG/MAG welding,was 2％CO2 in argon(Ar–2％CO2).The results of the studies are obtained on three samples with each powder-cored wire and data were averaged and presented in the paper.Microhardness measurement was done in sample cross section from the surface inward the sample.Microhardness was measured by Vickers method using a microhardness testing machine(HVS 1000A)under a load of 0.2 N and 0.5 N.Hardness measurements were performed after a natural aging of 1 month.