EFFECT OF LAVES PHASE PRECIPITATION ON REDISTRIBUTION OF ALLOYING ELEMENTS IN P92 STEEL

The P92 steel specimens were aged at 650 degrees C for 0 similar to 5000 h, and precipitates of the aged specimens were extracted from the matrix using carbon extraction replicas and potentiostatic electrolysis. The amount of alloy elements in extracted precipitates was determinded by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and EDS, then the redistribution of alloying elements owing to Laves phase formation was analyzed. The hardness of aged specimens was taken using a Brinell hardness tester. The damage evolution equation owing to solute depletion was obtained from the redistribution characteristic of alloying elements and its influence on the creep life of P92 steel was evaluated based on the physical CDM model. The results are as follows. Before aging, about 86% contents of W and Mo in P92 steel are supersaturated in matrix and the remains are in M23C6 carbides. The removing of alloy elements take place due to the precipitation of Laves phase during aging. The formation of Laves phase consumes mainly W and Mo in matrix, and has little effect on the compositions of M23C6 cabides and MX carbonitrides precipitated before aging. The partition coefficients of these two elements supersaturated in matrix reduce up to 50% on the completion of Laves phase precipitation, and the Cr content in the matrix decreases about 3.6% because the formation of the Laves phase consumes Cr. The precipitation of Laves-phase contributes to the significant decreasing of solution hardening, causes the creep life of P92 steel reduction of about 24% at 650 degrees C, 100 MPa.