Effect of contact stresses on strain-induced martensitic transformation and damage development in support unit element of hydraulic turbine

The elements of the hydraulic turbine guide bearing made of chromium-nickel stainless 12Kh18N10T steel are studied after long-term operation of the hydraulic unit. The calculation of contact stresses by the finite element method showed that stresses sufficient for fatigue failure occur in local areas of the working surface. The surface and subsurface layers destruction of elements during the cyclic loading is accompanied by both the formation of a ferromagnetic phase of strain-induced martensite and the active development of different defects, including fatigue cracks. Eddy current measurements are performed to determine the content of the strain-induced martensite. The presence of fatigue microcracks and other defects is revealed by metallographic studies of the damaged surface areas. A criterion for sorting of the elements under study is proposed which can be used during a repair of a hydraulic unit.