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Detailed microstructural analysis, as well as fatigue crack initiation evaluation, was carried out for electron beam (EB) welded . Fatigue test specimens were EB welded (full penetration) along their length, and a second weld pass, incorporating a slope-out from full to zero penetration along the gage length, was also applied. The specimens were fatigue tested at 523 °C and maximum stress (R ϭ 0) in the range 579 to 820 MPa. Early fatigue failure (Ͻ100,000 cycles at 0.25 Hz) was directly associated with the initiation at solidification porosity formed during "spiking" in the partial penetration weld metal at the start of the slope-out. The base metal, full penetration weld metal, and slope-out region were characterized using optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM), which indicated that the microstructures of the base metal and full penetration weld metal should give good fatigue resistance. The rapid solidification of the full penetration weld metal gave an interdendritic terminal solidification product consisting of ␥ ϩ NbC ϩ Laves phase instead of the usually reported eutectic ␥ ϩ Laves phase. Microstructural and chemical heterogeneities in the full penetration weld metal, combined with the sharp perturbations in penetration and solidification conditions (spiking) in the partial penetration weld metal, resulted in locally embrittled regions and interdendritic regions containing large numbers of fine pores as well as a higher volume fraction of mixed, hard interdendritic phases. These features would be consistent with a lower resistance to fatigue crack propagation in the partial penetration weld metal.

Abstract-Medical tools needs to be managed efficiently and sensibly from the initial step of procurement till being damaged. This includes acquiring procedure, operative procedures and the maintenance policies used in this regards. Managing the maintenance of medical tools is vigorous for the patient, medical doctors and for the hospital itself. One of the main complications in healthcare sector today is the availability of medical tools, which is mainly affected by downtime deviation needed to repair the medical tools.This research presents a process enhancement applied on the Downtime of the medical tools during the maintenance work in the Jordanian of Health Hospitals, based on adapted Six Sigma methodology-DMAIC-(Define, Measure, Analyze, Improve and Control). Data was collected from different locations for different tools to study and analyze the downtime problem and make the necessary actions to reduce it.

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