Long term creep properties and microstructure of SUPER304H, TP347HFG and HR3C for A-USC boilers

Abstract

SUPER304H (18Cr-9Ni-3Cu-Nb-N; ASME CC2328) and TP347HFG (18Cr-12Ni-Nb; ASME SA213) have been developed for high strength oxidation resistant steel tubes to operate at high steam temperatures and pressures. The longest creep rupture tests performed to date (600uC for 85 426 h for SUPER304H; 700uC for 55 858 h for TP347HFG) showed that the stable strength and microstructure were retained, with very little formation of s-phase compared with conventional austenitic stainless steels and no other brittle phases. The alloy HR3C (25Cr-20Ni-Nb-N; ASME CC2115) has been developed for the high strength and high corrosion resistant steel tubes used in recent ultrasupercritical (USC) boilers with steam temperatures of ,600uC. The longest creep test conducted to date (700uC, 69 MPa for 88 362 h) confirmed a stable creep strength and microstructure at 600-800uC. Superheater and reheater tubes of these alloys installed in the Eddystone No.1 USC power plant since 1991 have been removed and investigated. Updated long term creep rupture properties of the steels and microstructural changes during service are reported. Three steel tubes have been successfully applied as standard materials for superheater and reheater tubes in newly built USC boilers.

Advanced Austenitic Heat-Resistant Steels for Ultra-Super-Critical (USC) Fossil Power Plants

“…Its lattice parameter is about three times than that of austenite matrix. According to the results and the reported literature (Iseda et al, 2008), the main precipitated phases in HR3C steel are NbCrN phase, M 23 C 6 carbides and σ phase. NbCrN phase and M 23 C 6 carbides play an important role on strengthening effect.…”

“…Three typical newly developed austenitic heat resistant steels, TP347H, Super304H and HR3C, have been successfully serviced as superheater/reheater tubes in 600℃ USC power plants all over the world. Fig.4(a), (b) and (c) show creep rupture data for TP347H, Super304H and HR3C steels, respectively (Iseda et al, 2008). In comparison with these three creep rupture data, it can be seen that creep strength of Super304H at 650℃ is much higher than TP347H, and its long-term creep strength is even slightly higher than HR3C.…”

“…Mainly, there are three kinds of newly developed austenitic heatresistant steels such as TP347H, Super304H and HR3C have been used as superheater/reheater tubes extensively all over the world (Viswanathan et al, 2005;Iseda et al, 2008;Hughes et al, 2003). In this chapter, thermodynamic calculation, SEM, TEM and Three Dimensional Atom Probe(3DAP) technology were used to analyze the microstructure evolution of these advanced austenitic heat-resistant steels during aging at 650℃ till 10,000hrs.…”

Dissimilar metal welds between martensitic and advanced austenitic high temperature creep resisting steels: Creep rupture test results and fusion line investigation

“…Sadašnje projektne temperature od 650 °C su iznad maksimalno dozvoljenih radnih temperatura za martenzitne čelike i, kao posledica, moraju se koristiti nerđajući čelici ili nikl. Napredni austenitni nerđajući čelici kao što su X10CrNiCuNb18-9-3 (Super304HCu / DMV304HCu) i X6CrNiNbN25-20 (HR3C / DMV310N) su razvijeni da bi ispunili ovu ulogu [1] [2] [3]. Izbor ovih naprednih austenitnih nerđajućih čelika izaziva specifičnu potrebu za rešavanjem problema zavarivanja raznorodnih materijala (DMV), jer savremene elektrane od 600 °C takođe koriste komponente napravljene od niskolegiranih i martenzitnih čelika.…”

“…The current design temperatures of 650 °C are above the maximum allowable operating temperatures for martensitic steels and, as a consequence, stainless steel or nickel base alloys have to be used. Advanced austenitic stainless steels such as X10CrNiCuNb18-9-3 (Super304HCu/DMV304HCu) and X6CrNiNbN25-20 (HR3C/DMV310N) have been developed to fulfil this role [1][2] [3]. The selection of these advanced austenitic stainless steels provokes a specific need to address the issue of Dissimilar Metal Welding (DMW) because modern 600 °C power plants also use components made from low alloys and martensitic steels.…”