Mechanical and tribological behavior of TiB2/ Al2O3 coating on high-speed steel using electron beam deposition

Abstract

At 600 °C, a TiB2-Al2O3-Ti(20 %) coating was deposited by electron beam deposition (EBD) on high-speed steel (HSS) substrates. X-ray diffraction and field emission scanning electron microscope and energy-dispersive X-ray spectroscopy were used to investigate the structural analysis and surface morphology of TiB2-Al2O3-Ti(20 %) coating. The effect of load on Young’s modulus and hardness was studied using mechanical experiments on TiB2-Al2O3-Ti(20 %) coatings at modest loads ranging from 2000 to 10000 µN. Nanoscratch was done on TiB2-Al2O3-Ti(20 %) coated on HSS and uncoated HSS sample at a low load of 0–10000µN, and the coated sample had a COF of 0.08–0.21, whereas the uncoated sample had a COF of 0.2–0.46. To investigate the deformation and failure behavior of the coating/substrate combination and their nanotribological properties, nano wear experiments were done on TiB2-Al2O3-Ti(20 %) coatings at loads ranging from 0.5 N to 2 N. The results demonstrate that Young’s modulus and hardness of the TiB2-Al2O3-Ti(20 %) coating decreases when the load increases. The TiB2-Al2O3-Ti(20 %) coating has a coefficient of friction(COF) ranging from 0.08 to 0.17, indicating that it is self-lubricating, whereas the COF of uncoated HSS is 0.1–0.58. With increasing stress, the wear rate of TiB2-Al2O3-Ti(20 %) coating grows from 2.6808 × 10−3 to 4.461 × 10−3 mm3/m, while uncoated HSS wears from 6.4367 × 10−3 to 21.2 × 10−3. The TiB2-Al2O3-Ti(20 %) coating had smooth wear scars having no cracks/debris on the sample surface, indicating that the coated material flowed near the wear scar in a plastic manner.