Influence of hot dip galvanizing on fatigue and corrosion fatigue resistance of a B-Mn steel

In this study, the effects of hot dip galvanizing on fatigue and corrosion fatigue resistance of smooth and notched quenched and tempered (Q&T) specimens were investigated. Constant stress amplitude plane reversed bending fatigue tests (R=-1) at 47 Hz in air and sea water were conducted using cylindrical hot dip galvanized (HDG) and Q&T steel specimens made of a B-Mn SS2131(∼AISI 15B21H) steel with K t =1.05 and 1.7. The results are compared with those obtained for plasma-nitrided (PN) and laser-hardened (LH) specimens. The S-N curves show that hot dip galvanizing slightly decrease the air fatigue limit of smooth (-9%) and notched (-10%) specimens. In sea water, smooth and notched HDG specimens exhibit corrosion fatigue limits (at 2x10 7 cycles) with values a little lower than the corresponding air fatigue limits. The corrosion fatigue strength of HDG specimens is also superior to the fatigue strengths resulting from other surface treatments (plasma nitriding and laser hardening). It has been shown that the small cracks formed in the coating during galvanizing could be the cause of the slight decrease in air fatigue. Physical and electrochemical corrosion protection by hot dip galvanizing are the causes for the good corrosion fatigue properties obtained.