Issue 37

D. Angelova et alii, Frattura ed Integrità Strutturale, 30 (2017) 60-68; DOI: 10.3221/IGF-ESIS.37.08 63 5. Surface replicating of short fatigue crack growth. R ESULTS AND DISCUSSION A. Fretting fatigue tests he results of fretting fatigue tests are shown in Fig. 3a. The effect of hydrogen on tested steels is different: in 304 fretting fatigue limit is lesser in hydrogen gas (by 13 %) than in air, while in 316 - only slightly lesser; in 316L this limit is almost a) b) Figure 2 : Fatigue test: a) FATROBEM 2004 - electric engine 1, driving belt 2, ball-bearing unit 3, test box 4, specimen 5, loading device 6, counter 7, circulation-aeration device 8; b) Murakami specimen with a drilled hole of 100 µm; all dimensions in mm. a  (МPа) f N (cycles) a  (МPа) f N (cycles) a  (МPа) f N (cycles) 1 260 3433100 5 340 39600 8 400 129910 2 280 208670 6 360 154000 9 440 38940 3 300 315150 7 380 52030 10 460 9900 4 320 340010 Table 2 : Fatigue life at different stress ranges. the same as that in air [3]. At the same time there was no reduction of fatigue strength of Steel 304 in case of plain fatigue in hydrogen gas at low gas pressure condition [9]. On the whole austenitic stainless steels are relatively less affected by hydrogen gas (in terms of fretting fatigue strength) in comparison with aluminum alloys which strength decreases by nearly 60% in hydrogen gas [10]. The best “hydrogen immune” steel is 316L. T