45# steel is a widely used carbon structural steel, commonly known as "oil steel." It contains 0.45% carbon, hence the name 45# steel. It is extensively used in the manufacturing of mechanical parts due to its moderate hardness and ease of machining. After appropriate heat treatment, it acquires certain toughness, ductility, and wear resistance. For instance, after quenching and tempering, 45# steel exhibits excellent comprehensive mechanical properties, making it suitable for various critical structural components, particularly gears, shafts, bolts, and connecting rods subjected to alternating loads during operation. However, it has a low surface hardness and is not wear-resistant, so we quench and temper it followed by surface hardening to enhance the surface hardness.