Effect of Grit Blasting Parameters on Surface and Near-Surface Properties of Different Metal Alloys
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Effect of Grit Blasting Parameters on Surface and Near-Surface Properties of Different Metal Alloys Tina Ghara1 • S. Paul1 • P. P. Bandyopadhyay1
Submitted: 5 April 2020 / in revised form: 15 October 2020 / Accepted: 7 November 2020 Ó ASM International 2020
Abstract In thermal spray, grit blasting is the standard method used to prepare the substrate surface before coating deposition. This study examines the effect of the grit blasting parameters on the residual stresses, roughness and hardness of three metal alloys with widely different mechanical properties: low-carbon steel, Ti-6Al-4V and Inconel 718. It also estimates the density of dislocations using the Williamson–Hall method. The dislocation structures of low-carbon steel grit blasted at different grit impingement angles were observed under a transmission electron microscope. The surface dislocation density was found to increase with the blasting time and angle of impact. Moreover, the depth profile of the dislocation density was in good agreement with that of the hardness profile of the blasted specimen. The residual stress depth profiles of each material at different blasting pressure showed an increase in the value and depth of maximum compressive residual stresses. Both surface residual stresses and roughness were found to increase with the grit blasting pressure, angle and, to some extent, with time and stand-off distance. The mechanisms of material erosion were found to be microcutting and indentation at lower and higher angles of abrasive impingement, respectively. The extent of damage of the materials was explained on the basis of the Johnson–Cook flow strength model. Keywords dislocation density grit blasting indentation roughness residual stress thermal spraying
& P. P. Bandyopadhyay [email protected] 1
Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302, India
Introduction Surface preparation is a prerequisite to different processes, such as thermal spraying, welding and cladding (Ref 1, 2). The substrate surface is made suitable for obtaining superior mechanical bonding between the substrate and the deposited material using different methods (Ref 3). Abrasive blasting, also called as grit blasting, is one of the most effective surface preparation techniques in which irregularshaped abrasive particles are propelled at a high velocity toward the surface to be treated. Upon collision with the surface, the sharp edges of the abrasive particles remove a small volume of material by erosion. Repeated erosion of the substrate surface leads to the generation of a rough surface appropriate for coating adhesion. Microcutting, plowing and indentation led damages are the major material removal mechanisms in grit blasting (Ref 4, 5). The examples of frequently used abrasive materials are SiO2, Al2O3, SiC, diamond, ZrO2, steel slag (Ref 6), etc. Abrasive blasting also increases the hardness of the substrate surface through work hardening (Ref 7). Repeated impacts of abras
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