Study on temperature field, microstructure and properties of electroslag surfacing high chromium cast iron

In this paper, the high chromium cast iron (HCCI) hardfacing layer is deposited on the surface of D32 low-alloy steel by electroslag surfacing method. Combined with the temperature field measurement of the heat-affected zone (HAZ) during the surfacing process, the microstructure and mechanical properties of the HAZ, composite interface and hardfacing layer are studied. The results show that: the heating and cooling rates are slower during the electroslag surfacing, and the temperature distribution in the low alloy steel substrate during the stabilizing stage is uniform; the maximum temperature gradient in the surfacing direction is 23.1 ℃/mm. The maximum thermal stress in the low-alloy steel substrate is 25.9 MPa, lower than its tensile strength, which effectively avoids the occurrence of cracks; the composite interface is smooth and clear, with an austenite band region, about 50 μm in width; The grains of HAZ have grown, whose microstructure is a mixture of ferrite and pearlite. The microstructure of HCCI hardfacing layer is composed of austenite, carbides and a small amount of martensite. The M₇C₃ type carbides are small and uniformly distributed in austenite grain boundaries. The bonding strength of the composite interface is 96 MPa; the impact energy (53 J) of the composite sample is significantly higher than that of the HCCI hardfacing layer (10.7 J). During abrasion, the HCCI hardfacing layer undergoes martensitic transformation under a large load, the hardness is improved, and an excellent performance in wear resistance was obtained.