| Abstrakt: |
9Cr-1Mo steels are considered candidates for nuclear reactor applications, heat exchangers, boilers, petrochemical industries to achieve the higher efficiency. To enhance the performance against high temperature oxidation and corrosion during operations, Al O +FeAl coating through aluminizing has been widely Al2 o3 reported. Especially, for fusion reactors, this coating is a potential solution to overcome issues such as magnetohydrodynamic drag, tritium permeation & Pb-17Li corrosion attack. One of the critical issues associated with such coating techniques is fabrication sequence. The Al O oxide layer at the top may affect the 2 3 mechanical properties, due to the presence of Al in the weld zone. Moreover, the effect of coating on the welding properties such as depth to width ratio and micro-structures needs to be investigated. This experimental work attempts to investigate the effect fluxes on aluminized coated steels during Activated TIG (A-TIG) welding process. A-TIG welding is a relatively novel joining process which is a variant of TIG where different single component flux is applied before the welding to improve the depth of penetration. Six different fluxes such as Fe2O3, Al2O3, 2Co3 Co23O4, CuO, HgO and NiO were used for bead-on-plate 3 4 welding, carried out under same process parameters. for coated 9Cr steels. Experimental investigations indicated that due to the fluxes (oxides) the arc gets constrict and the depth of penetration increases for uncoated 9Cr-1Mo steels, whereas, in the case of aluminized coated steels, excessive penetration has been observed. The coating at the top which is an oxide (Al O), itself it is acting as a flux and Al2O3 responsible for higher arc constriction, consequently the current density increases and resulted in to excessive penetration. In this present investigation, the weld dimensions such as depth of penetration (DOP), depth/width (D/w) ratio, bead width (BW) and Heat affected zone (HAZ) width are analyzed and compared in addition to the peak welding temperatures. The different phases before coating and after welding are being analyzed through X-ray diffraction. The microstructure morphology of various flux coated samples will be investigated and the effect on grain size will be compared. The Al concentration in weld zone will be analyzed through elemental mapping with the help of SEM-EDX. Subsequently, the effect of fluxes on microhardness- microstructure co-relation of weld and HAZ will be studied. [ABSTRACT FROM AUTHOR] |
