Microstructure and Mechanical Properties of 18CrNiMo7-6 Steel Processed by Rotationally Accelerated Shot Peening
ZHU Min1, WU Guilin1, LI Yusheng2, HUANG Xiaoxu1
1 School of Materials Science and Engineering, Chongqing University, Chongqing 400030; 2 School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094
Abstract: In the present work, normalized and high temperature tempered 18CrNiMo7-6 steel was firstly subjected to rotationally accelerated shot peening (RASP) processing, which was a low-cost and efficient severe plastic deformation (SPD) technique to produce nanostructured surface-layers of metals. The microstructure of the steel after RSAP processing was characterized by optical microscopy (OM), scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD) techniques, and the mechanical properties were analyzed by microhardness measurements and tensile testing. Simultaneously, the effects of RASP parameters on the microstructural evolution and mechanical properties were analyzed. It is found that RASP successfully produced a steel with structural gradient and it had a obviously microhardness gradient form surface to the inner. Varying the shot peening velocity was an effective way to control the microstructure,while micro-cracks formed easily at the long shot peening time. With a peening velocity of 40 m/s and a peening time of 5 min,the sample had a harden surface without defects and the yield strength was improved by 57% to 512 MPa.
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2018, Vol. 32 
