Microstructure and Mechanical Properties of Modified AISI 4140 Steel with Addition of Cr and W Elements

High-temperature environments require materials with exceptional properties, including strength, oxidation resistance, and wear resistance. Quenched and tempered (QT) AISI 4140 steel, a chromium-molybdenum low-alloy steel, is known for its superior strength and toughness, making it widely used in industries such as automotive, aerospace, and oil & gas. The outstanding characteristics of 4140 steel stem from its alloying elements: chromium (Cr), molybdenum (Mo), and manganese (Mn), along with the quenching and tempering treatment temperature. These alloying elements facilitate carbide formation with carbon (C), resulting in finer grains and improved mechanical properties. This study aimed to enhance high-temperature performance by adjusting the chromium content, a key element influencing high-temperature properties. Modified AISI 4140 steel was produced using various QT treatment conditions. Tensile tests conducted at room temperature and at 400℃, 500℃, and 600℃ revealed that increasing the tempering temperature generally decreased tensile strength while increasing elongation. At 600℃, the tensile strength decreased for all specimens; however, higher chromium content and lower tempering temperatures improved the high-temperature strength of the modified 4140 steel.