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Detection of copper precipitates in 15 NicumonB5 (WB 36) steel by using micro-magnetic NDE techniques

	Japanese-German Joint Seminar on Structural Integrity and NDE in Power Engineering 2001 Tokyo, 2001 (Japanese-German Joint Seminar 8) pp.374-381
	Japanese-German Joint Seminar on Structural Integrity and NDE in Power Engineering <8, 2001, Tokyo>

	English
	Conference Paper
	Fraunhofer IZFP ()
	copper precipitation; micro-magnetic technique

Abstract
The material investigations presented confirm the results of earlier investigations with a conclusion that the service-induced hardening and decrease in toughness in WB 36 materials are caused by the precipitation of copper. In the initial state of the material, only a part of the alloyed copper is precipitated. The other part is still solved and can be precipitated during long-term operation at temperatures above 320°C to 350°C.
The copper precipitation leads to a distortion of the crystal lattice surrounding the copper precipitates and yields internal micro-stresses. If the number and size of the copper precipitates change during operation of a component, a change of the residual-stress level occurs.
The results obtained from load stress-related Barkhausen noise measurements demonstrate that these micro-magnetic procedures are generally suitable for the detection of copper precipitation.