The Effect of Silicon on Microstructure and Wear Resistance in Bainitic Steel

The microstructure, hardness and sliding wear behavior of bainitic steel containing 1.0-2.5% Si were investigated by means of the optical microscope, the scanning electron microscope, the X-ray diffraction, energy-dispersive spectroscopy, Rockwell hardness tester, microhardness tester and M-200 wear tester. The results show that the as-cast structure is mainly composed of acicular lower bainite and retained austenite. As the silicon content increases, the bainitic lath is refined, the retained austenite content is reduced, and the hardness tends to increase. After normalizing at 900 degrees C, the microstructure of the steel is mainly acicular lower bainite and film-like retained austenite. With the increase in Si content, the bainite needle is more refined, the retained austenite content is reduced, and the hardness is increased by about 20%. In as-cast and normalizing condition, as the silicon content increases, the wear loss of cast steel is reduced, and the wear resistance is improved. The wear loss of normalizing steel is obviously smaller than that of as-cast steel.