Effect of inclusion properties on corrosion performance of NM500 wear-resistant steel

    
    Abstract
    NM500 wear-resistant steel is an alloy steel which utilises a combination of chemical elements and specific heat treatments to provide superior protection against oxidation and corrosion. In this paper, the effects of common inclusion properties on the corrosion performance of NM500 wear-resistant steel, such as sulphide and oxides, are considered. Results show a decreasing trend of corrosion resistance with increasing sulphide and oxide inclusions. Additionally, a small degree of sulphide and oxide inclusions may actually improve the corrosion resistance of NM500 wear-resistant steel.
    
    Introduction
    NM500 wear-resistant steel is a type of alloy steel that is widely used in industrial applications due to its excellent oxidation and corrosion resistance. The oxidized and corrosion-resistant properties of NM500 wear-resistant steel are mainly due to the high levels of alloy additions, such as chromium, molybdenum, and vanadium, which raise the hardness, strength, and abrasion resistance of the steel. The presence of these alloy particles also restricts degradation caused by oxidization. Furthermore, the steel also undergoes heat treatments that result in a uniform distribution of residual oxides and nitrides, which in turn, enhance the corrosion-resistant properties of NM500 wear-resistant steel.
    
    Inclusion properties, such as sulphides and oxides, have been observed to have a significant effect on the corrosion resistance and other mechanical properties of the NM500 wear-resistant steel. In this paper, the effects of different inclusion properties on the corrosion performance of NM500 wear-resistant steel will be considered.
    
    Effect of sulphide inclusion on corrosion
    It has been observed that an increase in the amount of sulphide inclusion in the steel can significantly reduce its corrosion resistance. The structure of NM500 wear-resistant steel consists of a matrix containing small amounts of residuals, such as oxides and nitrides, and spherical shaped inclusions, such as sulphides and oxides. The presence of sulphide inclusion has been observed to reduce the crystalline structure of the matrix due to their size, shape and composition. The reduced crystalline structure of the matrix leads to a decrease in the corrosion resistance of the steel as less residuals are available to act as barrier against oxidation and corrosion. In addition, the presence of sulphide inclusions can also limit the mechanical properties of the steel, as they have been observed to act as stress concentrators and can cause weaknesses in the steel structures when they are in large numbers.
    
    Effect of oxide inclusion on corrosion
    The presence of oxide inclusions in NM500 wear-resistant steel has also been observed to have a significant effect on its corrosion resistance. It has been observed that an increase in the amount of oxide inclusion in the steel can decrease its corrosion resistance. The oxide inclusions, which are mainly composed of titanium, silicon and aluminum, can act as stress concentrators, leading to a decrease in the strength and ductility of the steel. Additionally, the oxide inclusions also degrade the crystalline structure of the matrix, reducing its corrosion resistance. Furthermore, the presence of oxide inclusions has been observed to decrease the oxidation and corrosion resistance of the steel due to the pores created in the structure.
    
    Conclusion
    In conclusion, the presence of sulphide and oxide inclusions in NM500 wear-resistant steel can significantly affect its corrosion resistance. Results show a decreasing trend of corrosion resistance with increasing sulphide and oxide inclusions. Additionally, it has also been observed that a small degree of sulphide and oxide inclusions may actually improve the corrosion resistance of NM500 wear-resistant steel. Further research is necessary to better understand the effects of different inclusion properties on the corrosion performance of NM500 wear-resistant steel.

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