Experimental Investigation of Hydrogen Embrittlement of 65Mn Steel with Small Punch Testing Method

The hydrogen embrittlement of the 65Mn used as the high strength spring material in Nuclear Power Plant is investigated with small punch testing method.During cathode hydrogen charging with the cur-rent density of 1mA,4mA,10mA and 20mA,the hydrogen atom is absorbed,diffused,segregated in the metal which causing the initiation of the brittle cracks.The specimens are punched after charging with small punch testing method.It is found that the maximum loading level,the total energy,the critical fracture strain and fracture stress reduce with the increment of the current density which means the strength and toughness re-duce.The macro fracture surface changes from the ductile fracture to the typical brittle fracture and the micro fracture properties change from the ductile voids to the intergranular brittle fracture.The hydrogen concentrations in the metal were analyzed with theoretical model.It was found with the increment of the current density,the hydrogen concentration increases.