P92钢Ⅳ型开裂的显微组织变化

Microstructure investigation on Type Ⅳ cracking in P92 steel

首先分析了P92钢焊接接头的显微组织和硬度分布,然后利用不同时间的P92钢焊接接头持久试验,分析了接头的蠕变损伤演化.结果表明,在650℃和70MPa下,经历3000h的持久试验后,P92钢焊接接头各微区均未发生明显的蠕变损伤;当持久试验时间超过4032h后,在细晶区(FGHAZ)和临界区(ICHAZ)内出现了大量的蠕变空洞,而粗晶区(CGHAZ)和焊缝金属中未出现蠕变空洞;当持久试验时间达到7000h后,细晶区和临界区中的蠕变空洞长大,并有相互连接的趋势;当试验时间达到7026h后,持久试样发生了脆性蠕变断裂,断裂位置在热影响区内,为典型的IV型蠕变开裂.

The microstructures and hardness distribution of P92 welded joint was analyzed,and the creep damages of the joints were observed under various times of creep tests at 650 ℃ and 70 MPa.It was found that no obvious creep damage was observed in the all zones of P92 welded joints for the 3 000 h creep specimen,many creep voids occurred in fine grain heat-affected zone and intercritical heat-affected zone regions and no creep voids were found in the coarse fine heat-affected zone and the weld metal in 4 032 h creep specimen,the voids grew up and tend to coalesce in 7 000 h specimen,and micro fissures began to form in 7 026 h specimen.Therefore,this creep fracture could be clearly identified as Type IV cracking.