Enhanced tribological properties of aluminium using laser-assisted tungsten coating

摘要

Aluminium (Al) suffers from poor wear and scratch resistance and also low surface hardness. To overcome this, the authors fabricated a ~200 pm coating of fine tungsten (W) powder on Al using laser surface alloying (LSA) with laser power and scanning speed varying from 400-800 W and 800-1,200 mm/min respectively. Material characterisation in the form of SEM and XRD, undertaken on the LSA samples, revealed novel microstructures including formation of intermetallic phases A14W. A1,2W that exhibit substantially higher hardness. Scratch hardness measurements further consolidated that surface hardness of coated samples was more than three times as compared to bulk aluminium. Scratch testing at normal loads of 50-150 N, scratch speed of 30 mm/min, demonstrated a stable friction coefficient of 0.6 and higher coating adhesive strength. When applied to automobile components and aerospace products, the micro-coated LSA samples can provide far better alternatives to the current industrial grade of aluminium from the tribology point of view.