ISSN:
1573-9325
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Conglusions 1. In the new blades, the fatigue crack initiates and propagates in the stable slip band in the (111) plane (stage I) restricted by one of the largest grains extending to the surface in the zone of the entry or exit edge or on the side of the vane. In subsequent stages, the crack propagates in the plane of action of the maximum tensile stresses. Passage of the crack front through the grains is accompanied by the formation of a relief which depends on the crystallographic orientation of the grain. Attention should be given to cyclic cleavage in the (100) plane with local shearing on three (111) planes. This is accompanied by the formation of rows of octahedral dimples with fine ductile striations. 2. The fatigue resistance and nature of failure of the new blades are determined by surface treatment and are almost independent of the heat treatment of the matrix. Fracture is intragranular. 3. Real service of these blades corresponds to the development of the process of recrystallization in the surface-hardened layer with formation of a fine-grained structure and subsequent segregation of harmful impurities at their boundaries and at the boundaries of the matrixgrains. This facilitates the nucleation of cracks in cyclic tests in testing units and the change of the mechnism of nucleation and propagation of the fatigue crack. Fracture is intergranular and fatigue crack formation is indicated only by the crystallographic branching of the main crack in the body of the grains.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01524463
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