Effect of deep tempering on microstructure and mechanical properties of G13Cr4Mo4Ni4V steel

Abstract

By means of the post heat treatment of deep tempering on the aviation bearing steel G13Cr4Mo4Ni4V after quenching and high-temperature tempering, the effect of the treatment on microstructure and mechanical properties of the steel was studied. Results show that, the deep tempering promotes the precipitation of carbides along the boundaries and on the bodies of martensite blocks. In this process, the block martensite structure is decomposed and refined. After three or more times of deep tempering treatments, the hardness of the steel is slightly improved due to the carbide precipitation on the boundaries and bodies of the martensite blocks and the growth of carbides. After 5 times of deep tempering treatments, the impact toughness and the elongation of the samples are slightly reduced, while the tensile strength is increased. The area of the crack propagation zone on the rotating-bending fatigue fracture increases, while that of the transient fracture zone decreases. The ultimate strength of the rotating-bending fatigue is increased from 560 MPa to 660 MPa, with the increased extent of 17.8%, which results from the decomposition and refinement of martensite blocks.

Investigation on Improved Hot Processing Map of Cr4Mo4Ni4V Aerospace Bearing Steel Based on Carbide Content

“…Taking the partial differentiation of Equation ( 4)-( 6) at fixed temperature, n 1 , β, and n are shown as Equation ( 7)- (9).…”

“…[1][2][3][4][5] Compared with high-carbon bearing steel, Cr 4 Mo 4 Ni 4 V steel inhibits the formation of V-rich and Mo-rich primary carbide MC and M 2 C in the casting process by reducing the C content [6,7] and significantly improves the fracture toughness and fatigue life. [8,9] Therefore, it is often used to manufacture aeroengine mainshaft bearing rings that serve in extreme working environments [10] of high DN value (the product of the inner diameter/mm and the rotation speed/rpm) and complex working conditions of rapid acceleration/deceleration, oil interruption, roll-sliding coexistence, etc.…”

Development and Prospect of Vacuum High-Pressure Gas Quenching Technology

“…Compared with ordinary gas quenching processes, the hierarchical gas quenching process is more flexible and effective in controlling quenching distortion. Yu et al [26] carried out graded quenching of 8Cr4Mo4V steel for aviation bearings at different temperatures under vacuum conditions. The vacuum step quenching and tempering process is shown in Figure 3.…”