Date of Award

10-30-2020

Publication Type

Master Thesis

Degree Name

M.A.Sc.

Department

Mechanical, Automotive, and Materials Engineering

First Advisor

Ahmet T. Alpas

Keywords

Mechanical, Automotive & Materials Engineering

Rights

info:eu-repo/semantics/embargoedAccess

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Abstract

The purpose of this work is to develop a bainitic heat treatment procedure for wear reduction in a medium carbon steel and compare the efficiency of this heat treatment with gas nitriding or electrochemical boriding surface treatments. Heat treatments were conducted on AISI 1045 steel blocks taken from an automotive component, namely an overrunning alternator decoupler (OAD) pulley bore using an induction heater. The samples were quenched in different quenching media of oil, melt salt and water. The hardness and microstructural transformation results were represented with cooling curves superimposed on the Continuous Cooling Transformation (CCT) diagram of the 1045 steel. The heat treated results indicate 820 °C induction heating for 2 minutes followed by 160 °C oil quenching for 15 seconds resulted in the lower bainitic and martensitic structures and the highest bainite percentage (~19.5 %). The sliding wear test was conducted with block-on-ring tribometer under dry, lubricated and humidity conditions. Volumetric wear loss was measured and calculated at different sliding distances. The relationship between the volumetric loss and working conditions showed that induction hardened steel followed by 160 °C oil quenching resulted in the lowest wear rate in both dry and lubricated condition due to the higher hardness and toughness of bainitic and martensitic structures compared to the untreated, nitrided and borided 1045 steel. In addition, it was found that the gas nitriding process produced the lowest surface roughness (0.35 - 0.37 μm) and the electrochemical boriding process produced the highest surface microhardness (1100 - 1300HV). The boric acid film was formed on the surface of borided steel after the SAP process (annealing at 750 °C followed by cooling in 40 % RH environment). It can be considered as a self-lubricated film to make the surface withstand sliding wear damage.

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