Effect of Vanadium and Nitrogen Contents on Microstructure and Properties of Wear-resistant Steel NM400
Vanadium and Nitrogen Contents on Microstructure
Vanadium (V) is added to the steel to improve its hardness, abrasion resistance and toughness while nitrogen (N) increases its strength and toughness. The microstructure of the steel is affected by the percentage of these two elements.
When the V and N contents are low (0.03~0.20 % and 0.02~0.14 %, respectively), the steel contain majorly ferrite and minor amounts of bainite or pearlite arrangement. This type of microstructure is usually observed for normal structural steels.
On increasing the V and N contents slightly (0.20~0.50 % and 0.14~0.25 %, respectively), the amount of bainite and pearlite increases while the ferrite content decreases. This defect can be corrected by heating the steel at approximately 800 °C followed by a tempering process.
On further increasing the V and N contents (0.50~1.00 % and 0.25~0.45 %, respectively), bainite or martensite becomes the dominant microstructure with sparse distribution of ferrite and pearlite. This steel has excellent wear and corrosion resistance and has a higher level of toughness than a martensite-pearlite steel.
Effect of Vanadium and Nitrogen Contents on Properties
The properties of the steel are predominantly affected by the V and N contents. When the V and N contents are low, the strength and hardness of the steel are relatively low but it exhibits a moderate degree of abrasion and wear resistance. This type of steel is usually used for structural applications.
On increasing the V and N contents, the strength and hardness increases significantly, making the steel wear and corrosion resistant. All these properties along with toughness of the steel make it suitable for use in field conditions. The steels having V and N contents of 0.50~1.00 % and 0.25~0.45 %, respectively exhibits highest ultimate tensile strength and hardness which makes them suitable for use in power plants and hydraulic excavators.
Conclusion
In conclusion, the microstructure and properties of the NM400 wear-resistant steel are affected by its V and N contents. A judicious control of the V and N contents enables to design a steel with desired properties. Higher V and N contents provide higher strength, hardness and wear-resistant properties making them suitable for use in heavy-duty power plants, hydraulic excavators and other industries for construction and maintenance of mechanical equipment.
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