Optimization Of Welding Parameters For Repairing NiAl Bronze Components And Rapid EDS Analysis On The Phases

The objective of this study is to determine an optimal welding procedure that can be implemented to repair damaged Nickel Aluminum Bronze (NAB) components. NAB is commonly used in marine applications where components are subject to a constant corrosive environment and high stresses, causing them to suffer from material degradation over time. The high cost associated with full replacement of damaged components make repair welding an appealing option to increase the remaining service life of components. Up to now, welding methods of NAB are rarely reported,and the phase analysis method used in this paper is also first used.Relevant standards were followed as fourteen welding procedures were developed and performed on a NAB test slab. Samples were cut out from the slab and prepared for analysis. The weld beads were inspected for flaws where three procedures were found to produce weld beads with undercutting and therefore were unsuitable as a repair procedure. Samples were then examined under an optical microscope where the microstructure was compared with what had been researched. Little variation was found between samples and they all showed a microstructure suitable for a marine application. Lastly a micro hardness test was performed to see the effect of welding and Post Weld Heat Treatment (PWHT) had on the hardness of the welded sections. With the exception of the welding procedures that produced a poor weld bead shape all the procedures tested are suitable for use as a repair technique. The small well shaped beads produced by procedure 7 and 8 make them the most optimum at this point in the research.Microarea phase analysis of parent metal and weld zone of NAB board was carried out by using Scanning electron microscope (SEM) / Energy dispersive X-ray spectroscopy (EDS) automatic phase determination techniques. The area distributions ofα,κIII andκI+κII+κIV mixed phases were collected, hence the area ratio of each phase, the weight ratio and mapping of each element were obtained. It was found that there are some widmannstatten structures in the weld zone of the sample without heat treatment, then the type, size, distribution of the phases in that with heat treatment are the same as parent metal, which demonstrated that the unfavorable widmannstatten structures and eutectoid structure had been converted intoαandκphases so it is believed that the welding and heat treatment parameters used in this article were reasonable. The electron backscatter diffraction (EBSD) technique was tried to further analyze theκI+κII+κIV mixed phase but the results showed that all the particles had same crystal structure, consequently theκI、κII、κIV phases were classified according to their shapes, sizes and location features. This study states that combined with EBSD microarea crystallography analysis, rapid EDS phase determination has the obvious advantages and application prospects.