The characteristics of interfacial intermetallic compounds (IMCs) can have serious impact on the reliability of solder joints. In this study, Ni nanoparticles (NPs) were added to SAC305 solder/Cu substrate interface by flux mixing. The effects of Ni NP addition on electromigration (EM) under high current density were investigated. EM tests with a maximum duration of 1128 h were conducted under a current density of 1 9 10 4 A/cm 2 , at 80 ± 3°C on the solders prepared using 0 and 2 wt% Ni NPs-doped flux. At 2 wt% Ni NPs addition to flux, the growth rate of interfacial IMC at the anode side decreased by more than five times. No significant change in electrical resistance was observed in 2 wt% samples for up to 1128 h. Ni NP addition at the solder/substrate through flux mixing is, therefore, expected to lead to more reliable solder joints.
Laser composite surfacing (LCS) is a photon driven manufacturing technology that can be utilized for depositing hybrid metal matrix composite coatings (HMMC) on softer Ti/Al/Mg alloys to enhance their tribo-mechanical properties. LCS offers the advantages of higher directionality, localized microstructural refinement and higher metallurgical bonding between coating and substrate. The current research presents the tribo-mechanical evaluation and characterization of solid lubricant based Ni-WC coatings deposited by LCS on Al-Si piston alloy by varying the concentration of graphite between 5-to-15-weight percentage. The tribological behavior of LCS samples was investigated using a ball-on-plate tribometer.Results indicate that the surface hardness, wear rate and friction coefficient of the Al-Si hypereutectic piston alloy were improved after LCS of graphite based HMMC coatings. The maximum surface hardness of 781H v was acquired for the Ni-WC coating containing 5 wt% graphite. The friction coefficient of Al-Si under dry sliding conditions was reduced from 0.47 to 0.21. The reduction in the friction coefficient was attributed to the formation of a shearable transfer layer, which prevented delamination and reduced adhesion, abrasion and fatigue cracking.
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