Experimental Study on Fatigue Crack Growth Behavior of Direct Aging GH4169 Superalloy

Fatigue crack growth tests were conducted on a CT specimen of a nickel base superalloy direct aging GH4169.The effects of thickness,temperature and stress ratio on fatigue crack growth behavior were studied separately.The key results are as follows:thickness has no effect on fatigue crack growth behavior in the thickness range from 4 mm to 10 mm,but as thickness is decreased to 2 mm,the fatigue crack growth rate decreases when stress ratio is 0.1;the effect of stress ratio on fatigue crack growth rate diminishes as stress ratio increases;increasing temperature accelerates fatigue crack growth rate,but the effect of temperature diminishes with the increase of stress intensity factor and the main mechanism for accelerating fatigue crack growth is oxidation.