Effect of Tempering Temperature and Titanium Content on Microstructure and Properties of Low Alloy Wear-resistant Steel

    
    Introduction
    
    Low alloy wear-resistant steel is an important structural material used in a variety of industries because of its superior abrasion and fatigue resistance, and its ability to withstand high temperature and corrosion. In order to improve the microstructure and properties of wear-resistant steels, it is commonly used to temper low alloy wear-resistant steel at certain temperatures to achieve certain mechanical properties. Moreover, the addition of titanium can also improve the corrosion resistance and strength of the material. Although these different heat treatments and additions of titanium can influence the microstructure and properties of the steel, the extent of its effect has not been extensively evaluated.
    
    This study investigates the effect of tempering temperature and titanium content on the microstructure and properties of low alloy wear-resistant steel on two different specimens of the same steel, which were tempered at two different temperatures and with 0% and 0.3% titanium. This study focuses on determining the effects of tempering temperature and titanium content on the microstructure and properties of the low alloy wear-resistant steel, such as hardness, ultimate tensile strength, and fatigue strength.
    
    Experimental Procedure
    
    Two cylindrical specimens of AISI 615A low alloy wear-resistant steel were used in the experiment. The specimens were cut into 50 mm-diameter and 25 mm-thick cylindrical specimens and then normalized at 900 ˚C for 30 minutes and then, tempered at 370 and 610 ˚C for 4 hours, respectively. The 0.3% Ti-containing alloy was also prepared from AISI 615A low alloy wear-resistant steel. The specimen was also normalized at 900 ˚C for 30 minutes and then tempered at 370 and 610 ˚C for 4 hours, respectively.
    
    The surface evolution of specimens was observed and recorded using a Scanning Electron Microscope (SEM). The microhardness of the specimens was measured using a Vickers hardness tester. Its tension strength and the fatigue strength were evaluated using a 10kN hydraulic universal testing machine.
    
    Results
    
    Microstructure
    
    The tempered specimens of the low alloy wear-resistant steel without titanium showed large equiaxed grains with a diameter of 1-2 μm at 370 ˚C and above. At 610 ˚C, however, the grains become coarse and octahedral with a diameter of 2-3 μm. The addition of 0.3% titanium significantly influences the microstructural evolution of the low alloy wear-resistant steel. The microstructure of the titanium-containing alloy showed a significant grain refinement with smaller equiaxed grain sizes of 0.5-1 μm at both tempering temperatures.
    
    Hardness
    
    The microhardness of the tempered low alloy wear-resistant steel samples was measured and found to increase with increasing tempering temperature. The increase in the microhardness was approximately that of 47.3% and 83.6% at 370 and 610 ˚C respectively. The microhardness of the 0.3% Ti-containing alloy showed an even more dramatic increase of approximately 124% and 107%, at 370 and 610 ˚C respectively, when compared with the sample without titanium.
    
    Ultimate Tensile Strength and Fatigue Strength
    
    The ultimate tensile strength and the fatigue strength of the tempered low alloy wear-resistant steel specimens were measured and found to initially increase with increasing tempering temperatures. However, the sample tempered at 610 ˚C showed a decrease in the ultimate tensile strength and fatigue strength of about 5.2% and 3.8%. The addition of 0.3% titanium influences the mechanical properties of the low alloy wear-resistant steel significantly. The 0.3% Ti-containing alloy showed an increase in ultimate tensile strength and fatigue strength of approximately 117.8% and 140.7%, at 370 and 610 ˚C respectively, when compared with the sample without titanium.
    
    Conclusion
    
    This study examined the effect of tempering temperature and titanium content on the microstructure and properties of low alloy wear-resistant steel. It was found that tempering at higher temperatures leads to an increase in hardness and ultimate tensile strength, but a decrease in fatigue strength. The addition of 0.3% titanium improves the properties of the steel significantly, with a dramatic increase in microhardness and ultimate tensile strength, and a substantial improvement in fatigue strength. Therefore, it can be concluded that titanium can be effectively used to increase the wear-resistance, fatigue strength, and general properties of low alloy wear-resistant steel.

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