PSI - Issue 14

Vikas Verma et al. / Procedia Structural Integrity 14 (2019) 68–77 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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Fig. 5. Wear results varying (a) load, (b) time, (c) speed

3.4 SEM observations of worn surfaces

Detailed analysis of worn surfaces of processed composites is done to identify the dominant mechanisms of material removal at the given sliding conditions. Representative SEM images of worn surfaces of investigated composites are shown in Fig. 6, Fig. 7 and Fig. 8. Figure 6 (a – f) represented the SEM images of the composites subjected at varying sliding loads. SEM image of pure Al alloy wear at 15 N (Fig. 6 a) reveals severe wear with characteristic grain pull-out and fracture. There is generation of cracks at high load of 25 N and grains pulled out as clusters as visible in Figure 6 (b). The critical wear is mainly due to the large surface damage and large amount aluminium transfer to the face accompanied through the generation of debris particles. At high load delamination of material is also observed. With addition of Fly ash and Al 2 O 3 , composite surface restricted the severe wear due to the increased hardness. Figure 6 (c) and (d) shows the SEM images of Al alloy +5%Fly ash +6%Al 2 O 3 and Al Alloy+5%Fly ash+9%Al 2 O 3 composites worn at 25 N. There is formation of oxide layer visible in the SEM micrographs which formed during continuous sliding. Material removes with some scratches as observed at low load and at high load grains are being pulled out because of the repeated sliding and adhere on the composite surface. Pulled-out grains are further compacted with continuous sliding and formed an oxide layer on the surface (Figure 6 f). Figure 7 (a, b) represented the SEM images of pure Al alloy and Al Alloy+5%Fly ash+12%Al 2 O 3 composite worn at 900 rpm. Figure 7 b SEM micrograph shows the formation of oxide layer in Al composite which is formed at high speed due to oxidation. Figure 8 (a, b) represented the SEM images of pure Al alloy and Al Alloy+5%Fly ash+12%Al 2 O 3 composite worn for 5 min. There is fracture and grain pull out observed in SEM micrograph of worn pure Al alloy whereas there is absence of cracks in the SEM image of Al composite having 5%Fly ash+12%Al 2 O 3 addition. Summarizing, Al Alloy+5%Fly ash+12%Al 2 O 3 composite is most preferred to survive at high load, at high speed and under longer duration of time.