E250 MPa [1300 MPa 1350 MPa 
citric acid citr hydroxid citric acid citr hydroxir 
304 3161 
steel, environment 
Fig.3: Fatigue life ratio for both steels in corrodants 
The detailed fractographic examinations of samples helped to elucidate the reasons of the 
fatigue life reduction. There were observed ductile fractures with some brittle fracture zones for 
both kinds of specimens — tested in corrodant and in air. Microcracks, microvoids and fatigue 
striations were found on the specimens fatigued in air and corrodant (Fig. 4). In some cases pits 
cd caused’ 50% initiated cracks in specimens tested in citric acid (Fig. 4b). Fractures of specimens and heat 
Ps An alkaline exchanger elements (Fig. 5) showed similar mechanism of structure degradation. 
- -- 7 
Fig. 4: Fractographs of fatigued specimens: a) 316L, air, 250 MPa, 10° cycles; b) 304, citric acid, 
250 MPa., 3-10° cycles; c) 316L, citric hydroxid, 250 MPa, 6,8 10° cycles; SEM 
311