Precipitation hardening martensitic stainless steel, turbine component formed of said martensitic stainless steel, and turbine including said turbine component

Abstract

It is an objective of the invention to provide a precipitation-hardening martensitic stainless steel having a far better balance between a high mechanical strength and a high toughness than conventional ones as well as having good corrosion resistance properties. There is provided a precipitation-hardening martensitic stainless steel throughout which precipitates of intermetallic compounds are dispersed, the martensitic stainless steel including: 0.1 mass % or less of C; 11 to 13 mass % of Cr; 7.5 to 11 mass % of Ni; 0.9 to 1.7 mass % of Al; 0.85 to 1.35 mass % of Mo; 1.75 to 2.75 mass % of W; and the balance including Fe and inevitable impurities, in which “[Mo content]+0.5×[W content]” is from 1.9 mass % to 2.5 mass %, and “[Mo content]/[W content]” is from 0.4 to 0.6.

What is claimed is: 
     
         1 . A precipitation-hardening martensitic stainless steel throughout which precipitates of intermetallic compounds are dispersed, the martensitic stainless steel comprising: 0.1 mass % or less of C; 11 to 13 mass % of Cr; 7.5 to 11 mass % of Ni; 0.9 to 1.7 mass % of Al; 0.85 to 1.35 mass % of Mo; 1.75 to 2.75 mass % of W; and the balance including Fe and inevitable impurities, wherein “[content of the Mo]+0.5×[content of the W]” is from 1.9 mass % to 2.5 mass %, and “[content of the Mo]/[content of the W]” is from 0.4 to 0.6. 
     
     
         2 . The precipitation-hardening martensitic stainless steel according to  claim 1 , further including 0.4 mass % or less of Ti. 
     
     
         3 . The precipitation-hardening martensitic stainless steel according to  claim 1 , wherein part of the Ni is substituted by 3 mass % or less of Co. 
     
     
         4 . The precipitation-hardening martensitic stainless steel according to  claim 1 , further including one or both of Nb and V in total amount of 0.5 mass % or less. 
     
     
         5 . The precipitation-hardening martensitic stainless steel according to  claim 1 , further including 0.1 mass % or less of Si and/or 1 mass % or less of Mn. 
     
     
         6 . The precipitation-hardening martensitic stainless steel according to  claim 1 , wherein the inevitable impurities include one or more of 0.5 mass % or less of P, 0.5 mass % or less of S, 0.1 mass % or less of Sb, 0.1 mass % or less of Sn, 0.1 mass % or less of As, and 0.1 mass % or less of N. 
     
     
         7 . The precipitation-hardening martensitic stainless steel according to  claim 1 , wherein one of the intermetallic compounds is β-NiAl phase. 
     
     
         8 . The precipitation-hardening martensitic stainless steel according to  claim 1 , wherein the precipitation-hardening martensitic stainless steel is solution heat treated at 850 to 950° C. followed by aging heat treatment at 450 to 650° C. 
     
     
         9 . A turbine component formed of the precipitation-hardening martensitic stainless steel according to  claim 1 . 
     
     
         10 . A turbine rotor including the turbine component according to  claim 9 , wherein the turbine component is a steam turbine long blade. 
     
     
         11 . A steam turbine including the turbine rotor according to  claim 10 . 
     
     
         12 . A thermal power plant including the steam turbine according to  claim 11 . 
     
     
         13 . A turbine component formed of the precipitation-hardening martensitic stainless steel according to  claim 2 . 
     
     
         14 . A turbine component formed of the precipitation-hardening martensitic stainless steel according to  claim 3 . 
     
     
         15 . A turbine component formed of the precipitation-hardening martensitic stainless steel according to  claim 4 . 
     
     
         16 . A turbine component formed of the precipitation-hardening martensitic stainless steel according to  claim 5 .