Steam turbine inner casing component and repair method therefor
Embodiments of the present invention relate to an inner casing component configured to form part of a steam flow path of a last stage of an axial flow steam turbine, the steam turbine inner casing component having a base made of nodular cast iron and a coating, on the base, in a region exposed to the steam flow path, consisting of manganese austenitic steel.
1. An inner casing component configured to form part of a steam flow path of a last stage of an axial flow steam turbine, the inner casing component comprising:
a base made of nodular cast iron; and
a coating applied to the base in a region exposed to the steam flow path, the coating comprising manganese austenitic steel defined by code EN 1.4370.
2. The casing component of claim 1 , wherein the last stage comprises a stationary vane row and a downstream rotating blade row, and wherein the region to which the coating is applied is radially between the rotating blade row and the base.
3. A method for manufacturing an inner casing component having a base configured to form part of a steam flow path of a last stage of an axial flow low pressure steam turbine, the method comprising the step of:
applying a coating of manganese austenitic steel to the base in a region exposed to the steam flow path, the manganese austenitic steel being defined by code EN 1.4370.
4. The method of claim 3 , wherein the last stage comprises a stationary vane row and a downstream rotating blade row; and wherein the step of applying the coating in the region exposed to the steam flow path comprises applying the coating to the inner casing component in a location radially between the rotating blade row and the base.
5. The method of claim 3 , wherein the coating is applied by welding.
6. A method for repairing erosion damage of an inner casing component configured to form part of a steam flow path of a last stage of an axial flow low pressure steam turbine, the method comprising the step of:
applying a coating of manganese austenitic steel to a base of the inner casing component in a region exposed to the steam flow path during operation of the steam turbine, the manganese austenitic steel being defined by code EN 1.4370.