1.  Waterwall

• Smelt corrosion  →  Composite tube
• Fatigue cracking →  (using High Ni alloy for outer)

2.  Superheater

• High temperature corrosion →  High Cr and Ni alloy 
• Stress corrosion cracking     →  Composite tube (using alloy steels for inner)

1.  Waterwall

• Composite tube

          304L/SA210A1,    310S/SA210A1

          825/SA210A1,      HR11N/SA210A1

2.  Superheater

• Mono-wall tube

          HR2M [KA-SUS309J2TB],  HR3CL  [CC2115-1],  (HR11N)

• Composite tube

          310S/T22,  25Cr-35Ni/T22

Fig.  High corrosion resistant steels for superheater of RLRB.

HR11N Properties

Fig.  High temperature corrosion test results.

In order to enhance a corrosion resistance at high temperature, HR11N has high Cr compared with alloy 825.

Localized corrosion

Fig.  Schematics of high temperature SCC and intergranular test.

Test condition

Fig.  High temperature SCC and integranular test results.

Mo, N addition is effective for increasing localized corrosion resistance.

Field service test of HR11N composite tube

Field service test conditions

Fig.  Field service test results.

Manufacturing composite tube

Fig.  Composite tube.

Fig.  Billet making process.

Fig.  Microstructure of bonded portion. (Outer: HR11N, Inner: SA210 Gr. Al)

Shipping record of composite tubes

Shipping record of composite tubes