Study of the microstructural evolution during austenitization of an ASTM A335 P91 steel.

Materia

Luppo, María Inés¹  Signorelli, Gisella Fernanda² 

[1] Gerencia Materiales, Buenos Aires, Argentina;UNSAM, Buenos Aires, Argentina

关键词: P91;    precipitates;    austenitization;    microscopy.;   

DOI  :  10.1590/s1517-707620180002.0371

学科分类：工程和技术（综合）

来源: Universidade Federal do Rio de Janeiro * Coordenacao dos Programas de Pos-Graduacao de Engenharia

【 摘 要 】

Quenched and tempered 9%Cr grade 91 steels (9Cr1MoNbVN) display a lath martensitic matrix with M23C6 (M = Cr, Fe) carbides and fine precipitates named MX (M = Nb, V; X = C, N). MX particles provide the key to control the size and size distribution of austenite grains, which is significantly important in designing materials with specific mechanical properties. In previous works it was reported that samples of a T91 steel austenized at 1050ºCfor times between 0 and 40 minutes following heating at a rate of 50 ºC/s exhibit a heterogeneous austenitic grain size distribution after austenite holding for 20 to 30 minutes from the austenite plateaus tart. Besides, it was observed that all the second phase particles coming from the as-received state are present at the beginning of the austenite holding and that the dissolution of the MM23C6 carbides and a change of the chemical identity of MX precipitates occur within the first 5 minutes of holding. In the present work the detailed evolution of second phase precipitates over the 5 first minutes of austenite holding, obtained by means of a high speed, high resolution dilatometer is studied and followed by scanning and transmission electron microscopy. M23C6 precipitates were not observed from the first minute of austenitization. MX precipitates change progressively their character from V-rich to Nb-rich. The observed diminution of the Ms temperature values would be related to the M23C6 carbides and V-rich MX carbonitrides dissolution.

【 授权许可】

CC BY