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利用划伤技术研究了690TT合金在325℃高温含氧硼锂水中的裂纹萌生和生长情况。试样表面和截面显微分析的结果表明,划伤沟槽底部局部萌生了典型的沿晶应力腐蚀裂纹。由于应力集中,在慢速率拉伸阶段划伤沟槽底部产生了机械裂纹,而机械裂纹成为恒载过程中690TT合金沿晶应力腐蚀裂纹萌生和生长的先导。尖端非常接近晶界或者沿着晶界的机械裂纹可继续形成沿晶应力腐蚀裂纹。690TT合金在恒载荷条件下对应力腐蚀开裂仍有一定的敏感性。
The crack initiation and growth of 690TT alloy in 325 ℃ oxygen-rich boron-lithium water were studied by using scratch technique. The results of microanalysis of the specimen surface and cross section show that typical intergranular stress corrosion cracking occurs at the bottom of the scratched trench. Due to the stress concentration, mechanical cracks were formed at the bottom of the scratched trench at slow rate and the mechanical crack became the precursor of stress corrosion crack initiation and growth of 690TT alloy during constant load. The tip is very close to the grain boundaries or along the grain boundary mechanical cracks can continue to form intergranular stress corrosion cracking. 690TT alloy under constant load stress corrosion cracking is still a certain sensitivity.