Influence of shielding gas on microstructure and properties of(Nb,Ti)C reinforced Fe-based composite surfacing layer

The hybrid carbide-reinforced Fe-based composite surfacing layer has attracted a great deal of attention due to its excellent hardness and wear resistance.In this paper,(Nb,Ti)C reinforced Fe-based composite surfacing layer was fabricated by gas shielded surfacing technology with three different shielding gases(pure Ar/80%Ar+20%CO2/pure CO2).For surfacing layers under different protective gas, precipitation process of(Nb,Ti)C, microstructure, hardness and wear resistance were analyzed.The results showed that surfacing layers fabricated with pure CO2 as shielding gas had the least amount of(Nb,Ti)C precipitation(0.44 pcs/μm2), which dispersed in the martensite matrix.O atoms infiltrated in the surfacing layer, microhardness was 620.3 HV, and weight loss by wear was 8.4 mg.As CO2 content decreased in the shielding gas, microhardness and wear properties of surfacing layer tended to increase, while pure Ar were used as shielding gas, amount of(Nb,Ti)C precipitation in surfacing layer was the largest(0.54 pcs/μm2), microhardness was 708.2 HV, and weight loss by wear was 0.8 mg, which was 9.5% that in pure CO2 shielding gas and showed best wear resistance.Wear form of surfacing layer was adhesive wear accompanied by fatigue wear and abrasive wear.When pure CO2 shielding gas was used in surfacing layer, it resulted in relatively serious adhesive wear.Precipitation of(Nb,Ti)C significantly improved hardness and wear resistance of surfacing layer.