Effect of Surface Nanocrystallization Method on Fatigue Strength of TA2

Abstract

The enhancement of the fatigue strength is significant for the engineering applications of commercial pure titanium and its alloys. The paper investigated improvement of fatigue strength for commercial pure titanium by combined high-energy shot peening. Firstly, nano-crystallization in surface layer of pure titanium was carried out by high-energy shot peening, and then the shot peening with small diameter shots was introduced to degrade the surface roughness, enhancing the quality of the nano-grained surface. The fatigue limit of pure titanium by high-energy shot peening turns out to be increased by 34%, and the fatigue limit of pure titanium by compound high-energy shot peening turns out to be increased by 52.3%, according to the results. Effective factors such as surface states etc. to fatigue life, the fatigue crack initiation and propagation behaviors were also discussed in this paper.

Fatigue behavior of notched steel specimens with nanocrystallized surface obtained by severe shot peening

“…The results are aligned with the few data available in the literature about the fatigue strength improvement of surface NC notched specimens, that although are quite disperse in terms of material, specimen geometry, surface NC process and test type, have all indicated of fatigue life improvement through surface nanocrystallization [16][17][18].…”

“…Repeening using low energy small shots was applied to decrease the surface roughness up to 40%. Comparing with the fatigue limit of NP specimens, the results were increased up to 9% by CSP, up to 34% by HESP and up to 52% after repeening [18].…”

“…Wen et al [18] studied the fatigue strength of pure titanium treated by high energy shot peening (HESP), through rotating bending fatigue tests performed on notched specimen (K t = 1.27). They mentioned that surface damage, roughness, and edge of specimen, reduced the fatigue limit and in some cases even caused the function of NC layer to be counteracted.…”

Enhancing heavy load wear resistance of AISI 4140 steel through the formation of a severely deformed compound-free nitrided surface layer

“…In this research, it is clearly showed that the pin-on-disc wear under heavy loads involves not only the surface scuffing, but also contact fatigue behavior. In addition to the compressive residual stress, USP treatment also introduced a worsening of the surface roughness, which will reduce the scratch resistance and facilitate crack initiation under fatigue loading [29,30]. Despite this, the severely deformed compound-free nitrided layer presented desirable wear resistance especially under heavy loads and the most important characteristic of the layer is the comprehensive performance supporting by the high hardness, toughness and the significantly enhanced residual compressive stress.…”

The Effect of Ultrasonic Peening Treatment on Fatigue Performance of Welded Joints

“…Weld toe grinding can effectively improve fatigue strength of a welded joint [ 13 , 14 ], but static strength may decrease after grinding. Shot peening is one of the most widely used surface enhancing methods to improve fatigue strength [ 15 , 16 , 17 ]. Fatigue properties of the parent metal treated by shot peening have been documented in detail by Bagherifard et al and Hassani-Gangaraj et al .…”