Abstract
Objective: Aluminium and its alloys components are used in aero and space industries where in many cases trioboloading prevails. In space application, in addition to triboloading, the components should also perform in the absence of atmosphere. In the present investigation, attempted has been made to simulate the field conditions in the laboratory by sliding Al6061 alloy pin of different diameters in a vacuum at different temperatures using a vertically configured pin-on-disc test rig. Method: The pin diameters were 2, 4, and 6mm and the testing temperatures were 373, 473, and 573K. The normal contact pressure was 0.625MPa and the sliding speed was 0.5ms-1 and both were constant throughout the experiment. The coefficient of friction was monitored using a PC and the worn pin surface was studied in scanning-electronmicroscope. Findings: The result showed that the coefficient of friction at sliding temperatures 373 and 473K was found to be dependent on apparent contact area i.e., pin diameters 2, 4, and 6mm. The coefficient of friction was found to be 3.27 and 2.69 for pin diameter 2mm at temperature 373 and 473K whereas the coefficient of friction was of the range 1.36 to 0.33 for the pin of diameter 4 and 6mm. The scanning-electron-microscopic study revealed uniform plastic deformation for pin diameter of 2mm and non-uniform plastic deformation accompanied with abrasion extrusion phenomenon for the pin of diameters 4 and 6mm. The coefficient of friction at sliding temperature 573K was found to be insensitive to the apparent contact area. The coefficient of friction was in the range of 1.24 to 2.30. The SEM study revealed a large scale of non-uniform plastic deformation accompanied by abrasion, tearing of ridges, extrusion of both ridges, and entrapped wear debris. Novelty: It is a generic study for understanding the response of aluminium for tribo loading which. Keywords: Pin on Disc (POD); Scanning Electron Microscope (SEM); High Temperature; Vacuum; Coefficient of Friction; Al6061 Aluminium Alloy 1
Highlights
Aluminium and its alloys are used in industries, aerospace, and space applications
The results showed that above 473 K testing temperature, the DLC coating exhibited higher Coefficient of friction and wear
The worn-out surface of the pin was studied in SEM for understanding wear mechanism and to correlate observed dependency of coefficient of friction with experimental variables like testing temperature, apparent contact area, and vacuum
Summary
Aluminium and its alloys are used in industries, aerospace, and space applications. The engineering components of aluminium and its alloys used in the above application are subjected to relative motions resulting in friction and wear of components. Gharam et al (7) conducted experiments at elevated temperatures using a pin-on-disc test rig for evaluating tribo response of cast 319 grade aluminium and carbon-based coating pair. Zhu et al (13) conducted experiments at elevated temperatures for evaluating tribo response of aluminium and ZrO2-C composite using a pin-on-disc test rig. The bimetal composite results in improved wear performance and was attributed to the phases θ -Fe4Al13, η-Fe3Al5, and Al2O3 Zhu et al (15) conducted experiments at elevated temperatures using a pin-on-disc test rig for characterizing tribo response of aluminium matrix composites reinforced with Al3Zr + α-Al2O3. The literature shows the research work of different author aimed in evaluating tribo response of a system where parameters like normal load, sliding speed, different coating material, testing temperature and vacuum were considered. The study is of a generic in nature and finds utility in tackling tribo problem encountered in elevated temperature and vacuum environment
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