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对 HT80,Hy140,Hy180,Hy240,HP9-4-20,pH13-8Mo 以及18Ni(200)马氏体时效钢测定了在空气中(16.7赫兹)和海水中(0.167赫兹)的疲劳裂纹扩长速率(da/dN)_(air)和(da/dN)_(cor)。采用的应力比 R=0.10和0.50。用(da/dN)_(cor)/(da/dN)_(air)的比率γ_(0.167Hz)作为评定海水对疲劳裂纹扩展的影响程度。所得结果如下:(1)615℃回火的 Hy140钢和 HP9-4-20钢的γ_(0.167Hz)值较低。(2)全部试验用钢在 R=0.10时,⊿K=50～100公斤/毫米3/2γ_(0.167Hz)获得最大值。在⊿K<20～40公斤/毫米~(3/2)和⊿K>250公斤/毫米~(32)时,海水对疲劳裂纹扩展速率没有影响。(3)在较低裂纹扩展速率下,γ_(0.167Hz)取决于 K_(max)和⊿K,而在较高裂纹扩展速率下则取决于⊿K。γ_(0.167Hz)的最大值决取于K_(max)。(4)得到18Ni(200)马氏体时效钢的γ_(0.167Hz)和脆性断裂的断口率之间有良好的对应关系。
The fatigue crack growth rates in HT80, Hy140, Hy180, Hy240, HP9-4-20, pH13-8Mo and 18Ni (200) maraging steel were measured in air (16.7 Hz) and seawater (da / dN) _ (air) and (da / dN) _ (cor). The stress ratios R = 0.10 and 0.50 are used. The effect of seawater on fatigue crack propagation was evaluated by the ratio γ_ (0.167Hz) of (da / dN) _ (cor) / (da / dN) _ (air) The results obtained are as follows: (1) The values of γ_ (0.167Hz) of Hy140 steel and HP9-4-20 steel tempered at 615 ℃ are lower. (2) The maximum value is obtained for all the test steels at R = 0.10 with ⊿K = 50-100 kg / mm 3 / 2γ - (0.167 Hz). Sea water has no effect on fatigue crack growth rate at ⊿K <20-40 kg / mm3 and ⊿K> 250 kg / mm3. (3) γ_ (0.167 Hz) depends on K_ (max) and ⊿K at lower crack propagation rates, and ⊿K at higher crack propagation rates. The maximum value of γ_ (0.167 Hz) is determined from K_ (max). (4) There is a good correspondence between the fracture rate of γ_ (0.167Hz) and brittle fracture of 18Ni (200) martensitic steel.