Laser cladding is a promising photon-based surface engineering technique broadly utilized for fabricating harder and wear resistant composite coatings. In spite of excellent properties, the practical applications of l...Laser cladding is a promising photon-based surface engineering technique broadly utilized for fabricating harder and wear resistant composite coatings. In spite of excellent properties, the practical applications of laser claddings are relatively restricted when compared with well-established coating techniques because of their inherent defects identified as cracks, pores and inclusions. Substantial evidence suggests that the incorporation of an appropriate amount of rare earth in laser claddings can remarkably prevent these defects. Additionally, the presence of rare earth in laser claddings can notably enhance tribo-mechanical properties such as surface hardness, modulus of elasticity, fracture toughness, friction coefficient and wear rate. In this literature review, the effect of rare earth in reducing dilution and cracks susceptibility of laser claddings in addition to microstructural refinement attained was examined. Mechanical and tribological properties of these claddings along with their underlying mechanism were discussed in detail. Finally, this article summarizes current applications of laser claddings based on rare earth and was concluded with future research directions.展开更多
Rapid Cu diffusion is one of the main causes of electromigration（EM） failure in lead-free solder joints.In this study, an effort has been made to investigate the detrimental effects of EM on microstructure and mecha...Rapid Cu diffusion is one of the main causes of electromigration（EM） failure in lead-free solder joints.In this study, an effort has been made to investigate the detrimental effects of EM on microstructure and mechanical performance of solder joint by introducing Co nanoparticles（NP） doped flux at the interface between SAC305 solder and copper substrate. EM tests were conducted on un-doped SAC305 and Co-doped SAC305 solder joints for different time intervals, with the maximum duration of 1128 h. A DC current was applied to the both types of solder joints to achieve a current density of 1 × 104A/cm2. EM tests were performed in an oil bath maintained at a constant temperature of 80 °C. It is found that Codoped flux significantly reduced the formation of cracks and voids at the cathode interface. Co atoms entered into the lattice of Cu6Sn5 leading to the formation of（Cu, Co）6Sn5. This thermodynamically stabilized the interfacial intermetallic（IMC） layers both at the anode and cathode sides and suppressed the change in their thickness. The average anodic growth rate of（Cu, Co）6Sn5 interfacial IMC in the doped sample was about one order of magnitude lower compared with that of Cu6Sn5 in the un-doped samples.Co-NP also improved the tensile strength considerably before and after EM. The report suggests that the reliability of solder joint during EM can be improved by using Co-NP doped flux.展开更多
基金Project supported by the University of Malaya Research Grant(UMRG,RP013A-13AET)University of Malaya Research Grant(UMRG,RP035A-15AET)
文摘Laser cladding is a promising photon-based surface engineering technique broadly utilized for fabricating harder and wear resistant composite coatings. In spite of excellent properties, the practical applications of laser claddings are relatively restricted when compared with well-established coating techniques because of their inherent defects identified as cracks, pores and inclusions. Substantial evidence suggests that the incorporation of an appropriate amount of rare earth in laser claddings can remarkably prevent these defects. Additionally, the presence of rare earth in laser claddings can notably enhance tribo-mechanical properties such as surface hardness, modulus of elasticity, fracture toughness, friction coefficient and wear rate. In this literature review, the effect of rare earth in reducing dilution and cracks susceptibility of laser claddings in addition to microstructural refinement attained was examined. Mechanical and tribological properties of these claddings along with their underlying mechanism were discussed in detail. Finally, this article summarizes current applications of laser claddings based on rare earth and was concluded with future research directions.
基金Financial support was provided by High Impact Research grant(UM.C/HIR/MOHE/ENG/26,Grant No.D000026-16001)from Ministry of Higher Education,Malaysia
文摘Rapid Cu diffusion is one of the main causes of electromigration（EM） failure in lead-free solder joints.In this study, an effort has been made to investigate the detrimental effects of EM on microstructure and mechanical performance of solder joint by introducing Co nanoparticles（NP） doped flux at the interface between SAC305 solder and copper substrate. EM tests were conducted on un-doped SAC305 and Co-doped SAC305 solder joints for different time intervals, with the maximum duration of 1128 h. A DC current was applied to the both types of solder joints to achieve a current density of 1 × 104A/cm2. EM tests were performed in an oil bath maintained at a constant temperature of 80 °C. It is found that Codoped flux significantly reduced the formation of cracks and voids at the cathode interface. Co atoms entered into the lattice of Cu6Sn5 leading to the formation of（Cu, Co）6Sn5. This thermodynamically stabilized the interfacial intermetallic（IMC） layers both at the anode and cathode sides and suppressed the change in their thickness. The average anodic growth rate of（Cu, Co）6Sn5 interfacial IMC in the doped sample was about one order of magnitude lower compared with that of Cu6Sn5 in the un-doped samples.Co-NP also improved the tensile strength considerably before and after EM. The report suggests that the reliability of solder joint during EM can be improved by using Co-NP doped flux.
