Research On The Deposited Structural's Characteristics And Double-wire Plasma Additive Manufacturing Process Of Iron-based Tungsten Carbide And High Nitrogen Steel

Aiming at the problem of wire arc additive manufacturing of high-strength and high-hardness additive structures,iron-based tungsten carbide is introduced as an enhanced hardening phase,high-nitrogen steel is used as the basic phase,and plasma arc is used as the heat source of refractory iron-based tungsten carbide wires.The process test of iron-based tungsten carbide within both high and low current range,the additive experiment of iron-based tungsten carbide and high nitrogen steel asynchronous double-wire interlayer overlapping component,and the synchronous double-wire homogeneous hardening component additive test were carried out.And the influence of the two materials ratio on the microstructure,microhardness,tensile properties,impact properties and dynamic mechanical properties were studied,which provides a theoretical basis and engineering application reference for structure-performance integrated design and additive manufacturing of the multi-dimensional,heterogeneous,high-strength and high-hardness additive components.Firstly,the plasma arc single-pass surfacing test of iron-based tungsten carbide wire was carried out in the high and low current ranges,and the microstructure and hardness properties under different current specifications were analyzed.The study found that the iron-based tungsten carbide powder core wire can be deposited with plasma arc very well.The deposited layer is mainly composed of?-Fe,?-Fe,Fe₃W₃C,unmelted W₂C and WC particle composition.The performance test shows that as the heat input increases,the tungsten carbide content decreases significantly and the hardness of the overlay layer decreases.Further,the iron-based tungsten carbide wire plasma arc single-layer multi-bead additive test research was carried out,and a good additive process specification was obtained.Tissue observation shows that there are a large number of dispersed second-phase particles at the junction of the weld beads,and they are more in the bottom than the middle.The results of the microhardness test show that as the inter-pass temperature decreases from 370°C to 30°C,the micro-hardness increases by about 16%,indicating that the inter-pass temperature will affect the hardness of the deposited layer.Then,the plasma arc additive test of the iron-based tungsten carbide and high-nitrogen steel synchronous double-wire homogenous hardened components was carried out.There are 4kinds of designs for single-bead multi-layer reinforced and hardened structures with a different ratio of iron-based tungsten carbide and high-nitrogen steel.Performance tests show that as the proportion of iron-based tungsten carbide increases,the microhardness of the additive structure increases,which is up to 1.27 times higher than that of high nitrogen steel,because of the presence of alloy carbides and residual tungsten carbide in the microstructure.The dynamic mechanical performance test shows that with the increase in the proportion of iron-based tungsten carbide,the dynamic stress intensity increases correspondingly,up to 1576MPa,which is 428MPa higher than high nitrogen steel.Finally,an exploratory experimental study of plasma arc additive materials for iron-based tungsten carbide and high-nitrogen steel asynchronous double-wire interlayer overlapping components was carried out.The interlayer overlap structure with the layer ratio of high nitrogen steel and iron-based tungsten carbide of 3?7 is designed,and found that when the ratio of iron-based tungsten carbide layers is high,cracks easily appear in the middle of the multilayer block.It is due to the excessively high WC hard phase ratio and high thermal stress.Microstructure observation revealed that there is a transition layer with an average width of about 130?m at the iron-based tungsten carbide-high nitrogen steel interface,while the transition layer of the high nitrogen steel-iron-based tungsten carbide interface is about 50?m.Within a height of 20mm,the microhardness will increase with the transition from high-nitrogen steel to the iron-based tungsten carbide deposited layer in the vertical direction.The average microhardness of first deposited layer of iron-based tungsten carbide among 5 additive components is between 423?447HV.