3rd TAGRA

Machine-tool spindles are critical components whose performance directly affects machining accuracy, product quality, and service life. Contact and sliding between the spindle surface and its supporting components during operation can lead to wear, consequently reducing spindle service life and adversely affecting machining quality. AISI 7131 steel is commonly used for machine-tool spindle applications due to its suitable mechanical properties and response to surface heat treatment. In the present study, the microstructure, hardness, microhardness, and wear behavior of AISI 7131 steel and carburized structural steel were investigated and compared. Samples of AISI 7131 and structural steel were carburized at 920 °C for 5 h, followed by hardening and tempering at 200 °C. Dry sliding wear tests were performed using a block-on-ring configuration under a load of 150 N and a sliding speed of 3.7 m/s for 40 min. Metallographic examination, hardness and microhardness measurements, and scanning electron microscopy (SEM) were employed to characterize the microstructure and surface properties of the samples. The results showed that the carburized AISI 7131 steel exhibited higher hardness and microhardness and superior wear resistance compared with the carburized structural steel. After 40 min of wear testing, the mass losses of the carburized AISI 7131 steel, carburized structural steel, and untreated AISI 7131 steels were 0.0126, 0.0382, and 0.0196 g, respectively. Microstructural observations revealed the formation of a martensitic surface layer in the carburized AISI 7131, which was attributed to its higher hardenability resulting from the presence of alloying elements, particularly manganese and chromium. In contrast, the carburized structural steel exhibited lower hardenability and a lower degree of martensitic transformation in the surface region. Overall, the results indicate that carburized AISI 7131 steel provides superior wear resistance and is a more suitable candidate for machine-tool spindle applications where high surface hardness and extended service life are required.