Simulation of thermal and mechanical performance of laser cladded disc brake rotors

Disc brakes wear during braking events and release airborne particulates. These particle emissions are currently one of the highest contributors to non-exhaust particle emissions and introduce health hazards as well as environmental contamination. To reduce this problem, wear and corrosion-resistant disc coatings have been implemented on grey cast iron brake disc rotors by using various deposition techniques such as thermal spraying and overlay welding. High thermal gradients during braking introduce risks of flaking off and cracking of thermally sprayed coatings with adhesive bonding to the substrate. Overlay welding by laser cladding offers metallurgical bonding of the coating to the substrate and other benefits that motivate laser cladding as a candidate for the coating of the grey cast iron brake discs. This study aims to investigate the effect of laser cladding on the thermal and thermo-structural performance of the coated grey cast iron brake discs. Therefore, thermal and thermo-stress analysis with COMSOL Multiphysics 5.6 software is performed on braking events of grey cast iron brake discs as non-coated – reference and laser cladding coated with stainless steel welding consumables. The Results demonstrated that surface temperatures were more localised, overall higher in the laser cladded coating with over three times the stresses attained of reference grey cast iron discs. The output of the simulations has been compared by tests found in the literature. Laser cladding presented higher reliability and braking performance, nonetheless requiring the evaluation of its thermal impact on other system components.

Weld Overlay Technique using Different Filler Rod Size to Overcome Internal Corrosion of Low Carbon Steel Base Metal

Overlay welding is commonly used to repair and replace the affected corroded surface of the base metal of a component. In other words, it is used to restore the original dimensions of the component. Weld overlay usually applies a corrosion resistant or hard facing layer onto the base metal. This experiment is to determine the suitable filler rod size in repairing corroded low carbon steel (LCS) base metal, respectively to the affected area and to identify the type of distortion occurring on the weldment. It is also to examine the microstructure of the joint between the overlay weld and corroded low carbon steel base metal using SEM/EDX. The overlay welding process was conducted on the corroded samples using SMAW process at defined attacked corroded areas. Filler electrode E-7018 with two diameter sizes of 3.2mm and 2.6mm were selected. It was found that the bigger electrode size produced higher degree of distortion angle compared to smaller electrode size. Resulting from the metallographic and SEM/EDX analysis, the joint between weld overlay and corroded LCS were fused well without any sign of oxides or other impurities present. Overlay welding also remove the sign of chloride ions that cause the LCS base metal to corrode. Thus, the repairing technique using overlay welding was found successful in repairing corroded LCS base metal. Therefore, the most suitable electrode size to do overlay welding on corroded low carbon steel base metal is 2.6 mm diameter electrode

Development of welding fluxes for hardfacing based on the mineral raw materials of the far eastern region

This paper presents the results of the research aimed at the creation of the ilmenite-fluorite welding flux using mineral raw materials of the Far Eastern region. The authors have performed thermodynamic calculation based analysis of the possible physical and chemical processes in the slag system. The experimental research we have conducted resulted in the mathematical dependencies that allow selecting flux components that would ensure the desired properties of the hard facing surfaces formed. Experimental overlay welding sessions were performed to determine the welding-technological characteristics and properties of the welded deposit. The results of the research show that the flux, consisting of 50 % of the mineral components extracted in the Far Eastern region and of 50 % of the standard flux АN22 is basic (В = 1.46) and has a low oxygenation capacity (А = 0.22). This facilitates reduction processes in the slag bath and, as a consequence of, results in obtaining high quality weld deposit. High level mechanical and performance properties of the coatings formed is maintained due to the reduction of alloying elements and possible formation of carbides (CrFe)7C3 or (CrFe)23C6, alloyed cementite (CrFe)7C3 and other substances. As an example, overlay welding under AN22PK-DMS flux produces the maximum content of chrome in the welded deposit of 12 – 15 %, and the maximum content of manganese of 6 %.

The Comparison of Cracking Susceptibility of IN52M and IN52MSS Overlay Welds

Overlay-welding of IN52M and IN52MSS onto CF8A stainless steel (SS) was conducted by a gas tungsten arc welding process in multiple passes. An electron probe micro-analyzer (EPMA) was applied to determine the distributions and chemical compositions of the grain boundary microconstituents, and the structures were identified by electron backscatter diffraction (EBSD). The hot cracking of the overlay welds was related to the microconstituents at the interdendritic boundaries. The formation of γ-intermetallic (Ni3(Nb,Mo)) eutectics was responsible predominantly for the hot cracking of the 52M and 52MSS overlays. The greater Nb and Mo contents in the 52MSS overlay enhanced the formation of coarser microconstituents in greater amounts at the interdendritic boundaries. Thus, the hot cracking sensitivity of the 52MSS overlay was higher than that of the 52M overlay. Moreover, migrated grain boundaries were observed in the 52M and 52MSS overlays but did not induce ductility dip cracking (DDC) in this study.