Effect of Environment on the Fatigue Crack Growth Behavior of Nitrogen-Alloyed Stainless Steel

Abstract The effect of the environment on the fatigue crack growth (FCG) behavior of SS316L(N) steel, under Constant R and Constant K max test conditions, has been analyzed using the two-parametric approach that considers amplitude Δ K and the maximum stress intensity factor, K max , are the governing load parameters controlling crack growth. The data for any selected crack growth rates plotted in terms of Δ K vs K max fall into L-shaped curves defining the limiting values for Δ K * and $$K_{\max }^{*}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mi>K</mml:mi> <mml:mrow> <mml:mo>max</mml:mo> </mml:mrow> <mml:mrow> <mml:mrow/> <mml:mo>∗</mml:mo> </mml:mrow> </mml:mmultiscripts> </mml:math> for each crack growth rate, starting from the threshold growth rate. The plot of these limiting values provides the material crack growth trajectory, showing the relative contributions of each on the crack growth rate in different environments. The results indicate that the K max contribution is dominant during crack growth in this alloy, particularly in corrosive environments. The time-dependent contributions during cyclic loads occur via the K max variable. In the present case, it can be predominately due to environmental effects. The fractographic evaluation provides further confirmation.