论文部分内容阅读
本文以40MnB和45Cr钢为材料,以3.5%NaCl的盐水为介质,在裂纹尖端基本上不存在应力腐蚀且裂纹中可产生腐蚀产物的条件下,试验研究了钢的回火态组织(200℃和500℃)对疲劳裂纹扩展的影响.试验结果表明:中碳钢的回火态组织对在盐水介质中疲劳裂纹的扩展有明显的影响.引起这一影响的主要原因是钢中所含的渗碳体型碳化物的数量,渗碳体型碳化物能构成微电池的阴极,经电极反应在裂纹内可产生腐蚀产物,它能降低腐蚀疲劳裂纹扩展速率.组织中含渗碳体型碳化物越多,该组织的腐蚀疲劳裂纹扩展速率降低就越为显著.所以,改变中碳钢的回火温度,就改变了钢中含这种碳化物的数量,也就改变了腐蚀疲劳裂纹扩展速率.疲劳断口和疲劳裂纹的显微观察表明,在盐水和空气中疲劳裂纹扩展途径基本相同.疲劳裂纹内腐蚀产物的量是控制(da/dN)_s的主要因素.
In this paper, 40MnB and 45Cr steel as the material, with 3.5% NaCl as a medium, the crack tip is basically no stress corrosion and corrosion products can be cracked under the conditions of the test tempering steel microstructure (200 ℃ And 500 ℃) on the fatigue crack growth.The results show that: the tempered microstructure of medium carbon steel has a significant impact on the fatigue crack propagation in saline medium.The main reason for this is the content of The amount of cementite carbides, cementite carbides can form the cathode of microcells, the electrode reaction can produce corrosion products in the cracks, it can reduce the rate of corrosion fatigue crack growth. The organization with more cementite type carbide , The more significant the corrosion fatigue crack growth rate is to decrease.Therefore changing the tempering temperature of medium carbon steel changes the amount of this carbide contained in the steel and also changes the rate of corrosion fatigue crack growth. The microscopic observation of fracture and fatigue crack shows that the fatigue crack propagation path in brine and air is basically the same, and the amount of corrosion products in the fatigue crack is the main factor for the control of da / dN.