Transcript cpri metal
MATERIAL CHALLENGES FOR ADVANCED STEAM PLANTS Dr. M. Shekhar Kumar Materials Technology Division Central Power Research Institute Bangalore Challenges Challenge faced by the power generation industry to meet increasing demand through increased efficiency and reduction of operation and maintenance costs and also meeting environmental and safety regulations Need for development of advanced materials Material changes over the years have resulted in operation at 170 bar and 540 C –efficiency of 35% Need to step up steam parameters Drawbacks on the boiler side Fireside corrosion of water walls and superheater Creep, Crack and Rupture Steam side oxidation Fracture toughness Thermal Fatigue Acid corrosion on the exhaust side Drawbacks on the Turbine side Strength, ductility and toughness Wear and erosion Creep, Crack and Rupture High cycle fatigue Scaling Embrittlement Lack of mechanical property data Material Options Super Alloys Ferritic Steels Stainless Steels Coatings Composites Intermetallics Material Considerations Strength to resist deformation and rupture at design conditions Fatigue strength and damping capacity when cycling stresses are involved Ability to resist stress concentrations Resistance to oxidation, corrosion and erosion Ability to resist damaging metallurgical changes during operation Ease of fabrication, field construction and maintenance Good physical properties to minimise thermal stresses Cost LOW ALLOY STEEL Low Alloy Steel 2 ¼ Cr-1Mo 4~5Cr-Mo High Strength Low Alloy Steelos 2 ¼ Cr-1Mo-V-Nb-(Ti) 4~5Cr-Mo-V-Nb-(Ti) Solution Strenmgthening -2 Mo --Mo-(W) --Mo-(W) Precipitate Strengthening Precipitate Strengthening -V-Nb , -V-Nb High Strength 9-12 Cr Steels With improved Weldability Low C , V0.3%, Nb 0.1 % Ti , Others 9-12 Cr Steels 9 Cr 9 Cr 12 Cr Austenitic Steel 18 Cr-8 Ni Solution Strengthening Type 316 (Mo) Precipitate Strengthening Cr-Carbide, Cr-Nitride Stabilising Type 321 (Tic) Type347(NbC) Improved 18Cr-8Ni Steels Optimization of 300 Series Stainless Steels Under Stabilizing Type A-1 (TiC, NbC) Type 304 Alloy Design for Elevated Temperature Application 15 Cr-15 Ni Type 17-14 CuMo High Strength Austenitic Steels 25Cr-20Ni Type 310 Highperformance 20-25 Cr Austenitic Steels 21 Cr-32Ni Type 800H Candidate Boiler Materials Component 31.0 Mpa (4500psi): 565/565/565ºC 31.0 Mpa(4500psi): 565/565/565ºC 34.5 Mpa (500 psi) 565/565/565ºC Furnace wall 1Cr-1/2 Mo(T12) 1 ¼ Cr- 1/2 Mo(T11) !Cr-1/2 Mo(T12) or 1 ¼ Cr –1/2 Mo(T11) For Lower wall; Super 9 Cr Same as phase 1 Super 9 Cr(T91) HCM12 304SS HR3C Chromised 347 SS Tempalloy A-1 347SS HR3c Chromised 347SS NF709 1714 Cu-Mo Esshete 1250 Finishing Reheater Same as above Same as above Shot blasted 347H Headers and Steam Pipes 2 ¼ Cr- 1 Mo(P22) 316 H Super9 Cr (P91) 9 Cr-2Mo(HCM9M 12 Cr-Mo-V(Ht(0 9Cr-Mo-W(NF616) 316H Finishing Super heater Non Coorrosive Corrosive NF709 CR30A Inconel 617 17-14 Cu Mo Chromised or Extruded with Incone l 671 or 310 SS MATERIALS FOR STEAM TURBINES TURBINE PARTS 565 C or LOWER STEAM TEMPERATURE 595 C 620 C or HIGHER SP,VHP,HP,VHP+H P,IP ROTOR Cr-Mo-V STEEL 12% Cr STEEL AUSTENTIC SUPER ALLOY INNER CYLINDER Cr – Mo STEEL 9 % Cr STEEL 316 AUSTENTIC STEEL BLADE HEAT RESISTANT SUPER ALLOY STEAM VALVE Cr- Mo STEEL or 9% Cr STEEL 316 AUSTENTIC STEEL ( FORGING ) NOZZLE BOX Cr – Mo STEEL or 9% Cr STEEL 316 AUSTENTIC STEEL ( CASTING or FORGING ) INLET STEAM PIPE Cr – Mo STEEL 316 AUSTENTIC STEEL ( FORGING ) OUTER CYLINDER Cr – Mo STEEL ( CASTING ) LP ROTOR Ni – Cr – Mo – V STEEL FOR 595 C or HIGHER, IMPROVED MATERIAL or ADVANCED MATERIAL FREE FROM EMBRITTLEMENT Conclusions Advances in materials development need focus Potential use of ceramics, ceramic matrix composites and ceramic/metal joining technologies Protective coatings Emphasis on materials for efficiencies greater than 55% Allied services