Mechanical,corrosion and tribological behavior of friction stir processed AZ31B/egg shell /WS 2 hybrid surface composite

Abstract

In the present work, egg shell and Tungsten disulphide particles are reinforced in AZ31B alloy using friction stir process. Initially, the ES and WS₂ particles are mixed at different weight ratios (25/75, 50/50 and 75/25) then are reinforced in AZ31B plates using a taper threaded FSP tool at rotation speed of 1000 rpm, axial load of 6 kN and traverse speed of 10 mm/min in hole method. The post macroscopic analysis showed that defect free hybrid surface composite is obtained with 75wt %ES and 25wt % WS₂ particles reinforced in AZ31B alloy. The grain size is reduced from 15 µm to 5 µm due to the addition of 75wt% ES and 25wt% WS₂ particles through FSP. The mechanical, corrosion and tribological responses of AZ31B/75ES/25WS₂ hybrid surface composite are observed and are compared with FSPed AZ31B alloy without reinforcements and AZ31B base alloy. The microhardness is improved by 66% and 83% in FSPed AZ31B alloy and AZ31B/75ES/25WS₂ hybrid surface composite respectively compared to the AZ31B base alloy. Similarly, the ultimate tensile strength is improved by 16% and 31% in FSPed AZ31B alloy and AZ31B/75ES/25WS₂ hybrid surface composite respectively compared to the AZ31B base alloy but the % of elongation is decreased by 70% and 78% in FSPed AZ31B alloy and AZ31B/75ES/25WS₂ hybrid surface composite respectively compared to the AZ31B base alloy. The corrosion rates of FSPed AZ31B alloy and AZ31B/75ES/25WS₂ hybrid surface composite are decreased by 22% and 48% respectively compared to AZ31B base alloy. The dry sliding friction and wear responses are observed for AZ31B base alloy and AZ31B/75ES/25WS₂ hybrid surface composite by varying the applied load (10 N, 20 N and 30 N) and sliding velocity (1.5 m/s, 2.6 m/s and 3.6 m/s) with constant sliding distance of 2000 m. In AZ31B base alloy, the wear mechanism is initially dominated by delamination and ploughing phenomena but at high sliding condition, the delaminated and worn out debris based tribolayer reduced the wear rate. In AZ31B/75ES/25WS₂ hybrid surface composite, the wear mechanism is dominated by adhesive and delamination phenomena and the formed tribolayer decreased the wear rate at high sliding condition.