ISSN:
1662-8985
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Directionally solidified (DS) superalloys, which have elongated large grains, are used forgas-turbine blades. Since the grain size is not small enough in comparison with the crack sizeobserved often in a real component, the inhomogeneous microstructure due to the aligned grains maystrongly affect the crack propagation property. Center-cracked-plate specimens with three differentorientations, TP0 with the parallel DS axis to the load, TP90T with the perpendicular DS axis to theload and the crack propagation direction, and TP90L with the perpendicular DS axis to the load andparallel to the crack propagation direction, are subjected to high-temperature (1143K) fatigue. Thespecimens after the tests show the transgranular cracking perpendicular to the load axis in TP0,intergranular one parallel to the DS axis in TP90L, and intergranular / transgranular one parallel to theDS axis in TP90T. The crack propagation rate da/dN shows a good correlation with effective stressintensity factor range [removed info]Keff in each cases. However, the magnitude of da/dN at a same [removed info]Keff in TP90Lis relatively higher than that in TP0, and that in TP90T remarkably fluctuates. A microscopicobservation of TP90T reveals that the high da/dN is caused by the intergranular cracking, while thelow da/dN is observed on the transgranular cracking. A procedure for the prediction of crackpropagation is proposed on the basis of the two types of cracking; transgranular and intergranularcracks perpendicular to the load axis. The validity of the proposed procedure is discussed by thecomparison of tested and predicted results of crack propagation in a fatigue condition
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/01/40/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.33-37.205.pdf
