Influence of shot peening versus laser peening on the fatigue behavior of superferritic stainless steel

R. STRUBBIA; A. CHÁVEZ-CHÁVEZ; S. HEREÑÚ; C. RUBIO-GONZÁLEZ; L. SPADARO; G. GOMEZ-ROSAS

Cancún

Congreso; XXV International Materials Research Congress (IMRC 2016); 2016

Laser shock peening (LSP) is an established mechanical surface treatment technology, which is generally utilized to improve fatigue performance. Compared with the conventional shot peening method (SP), LSP induces deeper compressive residual stresses into the material surface with a lower surface roughness. However, if absorbent coatings are not used in LSP operation, thermal effects can occur on the metallic substrate which could cause detrimental effects on the fatigue life. The purpose of this work is to compare the influence of laser peening and shot peening on the low cycle fatigue behavior of a superferritic stainless steel UNS S 44600.The LSP, without protective coating, was carried out using Q-switched Nd:YAG laser, operated at fundamental wavelength of 1064nm, energy of 1 J/pulse, repetition rate of 10Hz. The pulse density was 5000 pulses/cm2. The SP was performed using S-460 (1 mm) with Almen-intensity of 1 A. Roughness, residual stress and microhardness measurements were carried out on the treated specimens. Fatigue tests were conducted at room temperature under fully reversed plastic strain control, with plastic strain ranges of Δεp = 0.1%. The steel microstructure was analyzed by optic microscopy (MO) and transmission electron microscopy (TEM).SP and LSP induce beneficial compression residual stresses on fatigue life. Whereas the advantages of these induced residual stresses compensate the intergranular corrosion in LSP samples, they cannot counterbalance the detrimental effects of the high surface roughness of SP samples.