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Bahramian, Nasim

University of British Columbia

Next-generation internal combustion engines demand new materials to meet efficiency mandates regarding energy conservation and emission reduction. Replacing heavy ferrous metals with lightweight aluminum (Al) alloys considerably reduces the engine weight, improving its efficiency. However, most Al alloys suffer from poor tribological characteristics, the deriving factor for emerging technologies protecting Al components. In automotive engine blocks, a traditional method is to embed cast-iron liners within the cylinder bores to protect them from combustion harsh condition. However, this method poses challenges like generation of residual stress during casting which demands costly heat treatment processes. Linerless engine blocks equipped with advanced thin coatings have attracted original equipment manufacturers for a few decades. These coatings offer advantages such as light weighing and the flexibility in using optimized material for specific application. Among them is the plasma transferred wire arc (PTWA) coating mass produced in Ford Mustang GT500 engines. Despite its relatively high tribological properties, the coating’s mechanical bonding to the substrate is a concern in terms of durability and engine lifetime. Recently, a cost-effective and environmentally friendly coating technology called Electrolytic Jet Plasma Oxidation (EJPO) has been under development with the ability to produce strong chemical bonding to the Al substrate. This study aims at characterizing the new EJPO and existing PTWA coatings applied to two V8 engine blocks, from microstructural and surface topography aspects. The results distinguished each coating’s characteristic to resist scuffing in engine’s oil starving condition. While the PTWA coating showed the evidence of anti-friction solid lubricant phase (FeO) in its microstructure, EJPO one was featured by its superior surface topography. The comparison of the coatings’ bearing area curves revealed higher valley depth (4.5 times) and core roughness (1.9 times) for the EJPO coating compared to the PTWA one. Further, the EJPO coating oil retention capability is estimated to be 9 times higher than its counterpart. In the next study phase, a custom- tribometer was designed and manufactured for the future tribology study at UBC_HPPM lab. The machine was successfully run at a wide range of velocity, up to 1800 RPM, and normal load (up to 450N) with negligible vibration.

Text

2022-10-28

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/83080

Mechanical Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/