Abstract
Room temperature fatigue crack growth behavior was obtained for 4140 parent steel, parent heat treated (same as PWHT), as-welded HAZ and PWHT HAZ material under R≈O constant amplitude loading and single tensile overloads with an over load ratio (OLR: Pover/Pmax) of 2.5. Double pass automatic submerged arc welding with AWS EM2 electrode was used. PWHT was performed at 650°C for one hour. Constant amplitude fatigue crack growth behavior was very similar for all four material conditions in the log-log linear Paris region. All material conditions responded favorably to the single tensile overloads with fatigue crack growth retardation ranging from 2.5×105 to 4.5×105 cycles which corresponded to life increases of 250 to 400 percent. SEM analysis indicated many similarities on the fatigue fracture surfaces with predominant ductile quasi-striation morphology.
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