Effect of inclusions on very high cycle behaviour in a ferritic corrosion resisting steel

✍ Scribed by František Nový; Otakar Bokůvka; Peter Palček; Mária Chalupová

• Publisher: Elsevier
• Year: 2011
• Tongue: English
• Weight: 394 KB
• Volume: 10
• Category: Article
• ISSN: 1877-7058
• DOI: 10.1016/j.proeng.2011.04.234

✦ Synopsis

The number of structural components which must operate frequently at repeated loading higher as N ≈ 10 6 -10 7 cycles increases. This fact is serious problem in engineering practice. Fatigue lifetime in the ultra high cycle region (10 8 < N< 10 11 cycles) is therefore studied very intensively with the aim to correctly select the structural material. The paper is devoted to an experimental examination of the fatigue lifetime of X12Cr13 corrosion resisting steel used in the power industry. The high frequency fatigue testing (frequency f ≈ 20 kHz, temperature T = 20 ± 10C, sinus push-pull loading with load ratio R= -1) was used with the aim to obtain experimental data in the high cycle and ultra high cycle region (from N ≈ 10 6 to N ≈ 10 11 cycles). The obtained S-N curve revealed a continuous downward slope without any indication for plateau region, whereby surface (in the region 10 6 < N< 10 9 cycles) and subsurface (N > 10 9 cycles) fatigue crack initiation occurs in the used range of loading amplitudes. The inclusions of type Al 4 Ca and Al 2 Ca were the places of subsurface crack initiation; their role is discussed with regard on the fatigue lifetime of the X12Cr13 steel with ferritic matrix. Obtained results confirm that occurrence of those inclusions must be taken in consideration in application of the X12Cr13 steel for very high cycle service in power industry.