Issue 37

D. Angelova et alii, Frattura ed Integrità Strutturale, 30 (2017) 60-68; DOI: 10.3221/IGF-ESIS.37.08

400 Emery polished surface

Ground surface

Mirror finished surface

Steel

Unfretted

Fretted in air

Unfretted

Fretted in air

304

192

293

369

330

416

316

182

294

301

–

–

316L

172 285 Table 3 : Micro Vickers Hardness of fretted surface (Indentation load = 0.245N) 271 290 283

Formation of martensite due to fretting is observed in Steel 304 and not in 316L; it is found as well that hydrogen absorption in 304 contributes to decrease of fretting fatigue strength through: (a) hardening; and (b) formation of martensite due to fretting [3].

200

100

SUS 304 in air SUS 316 in air SUS 316L in air

0

Fretting fatigue limit (MPa)

0 100 200 300 400 500 Vickers hardness HV

a)

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 100 120 140 160 180 200 220 240 Stress amplitude,  a (MPa) Tangential force coefficient, ф . H2 Air H2 Air H2 Air Ground Polished SUS 316L SUS 304 SUS 316L SUS 304 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 100 120 140 160 180 200 220 240 Stress amplitude,  a (MPa) Tangential force coefficient, ф . H2 Air H2 Air H2 Air Ground Polished SUS 316L SUS 304 SUS 316L SUS 304 b) Figure 4 : Fretting fatigue [3]: a) Dependence “Fretting fatigue limit – Vickers hardness”; b) Tangential force coefficient.

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