Microstructure, performance and fracture analysis of medium carbon and medium chromium wear-resistant steel

Wear-resistant steels have been used for high load machinery components in the form of rolls, bearings and other host components due to their high strength, excellent wear resistance and high temperature oxidation resistance. In order to improve its wear resistance, the surface hardening methods of wear-resistant steel such as medium carbon steels and high chromium steels are the most suitable ones. Medium carbon and medium chromium wear-resistant steels are widely used in various industries. The characterizing features of these steels are their excellent mechanical properties, thermal shock resistance and resistance to wear, corrosion and embrittlement. These properties of wear-resistant steel make it suitable for the applications involving high mechanical loads and extreme working conditions.
    
Generally, wear-resistant steels are usually made with a specific combination of alloying elements like carbon and chromium. The microstructure of medium carbon and medium chromium wear-resistant steel consists of martensite at the surface which provides the higher wear resistance and is present in the form of pearlite and ferrite in deeper layers. This microstructure of the material results in increased hardness at the surface and increased wear resistance compared to other carbon steels.
    
The performance of this wear-resistant steel is usually determined by its mechanical properties like tensile strength, fatigue strength, wear resistance, corrosion resistance and thermal shock resistance. The wear resistance of this steel is mainly affected by the hardness of its surface layers and the presence of retained austenite or carbonitride layer which resists wear. This steel also has good thermal shock resistance due to its low coefficient of thermal expansion which allows it to expand and contract evenly with sudden changes in temperature. The corrosion resistance of this steel can be improved further by adding chromium to the surface layer of the material which takes part in the formation of protective chromium carbide layer.
    
Fracture analysis plays an important role in understanding the mechanical behavior of a material under applied loads. In the case of wear-resistant steel, the fracture analysis involves investigating the common fracture mechanisms such as fatigue cracking, wear, creep failure, adiabatic shear cracking and stress corrosion cracking. These mechanisms can be evaluated using different types of tests like hardness tests, micro-hardness tests, tensile tests, impact tests and creep tests. By analyzing the results of these tests, it is possible to determine the opening load of wear-resistant steel, its fatigue limits, the magnitude of the stress needed to propagate cracks and the rate of crack propagation.
    
To conclude, medium carbon and medium chromium wear-resistant steels are mostly used for heavy-duty applications due to their excellent mechanical properties, wear resistance and corrosion resistance. The wear resistance of this steel is mainly affected by the martensite layer at its surface and the presence of retained austenite or carbonitride layer. Moreover, fracture analysis of this steel helps in understanding the behavior of the steel under applied loads by investigating the mechanisms such as fatigue cracking, wear and stress corrosion cracking.

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