Modelling of specific grinding energy for Inconel 718 superalloy

Abstract

The present work is an attempt to model the components of specific grinding energy in a pragmatic manner. This work explores the contribution of specific energy constituents such as shearing, primary rubbing, secondary rubbing, and ploughing energy while grinding Inconel 718 (IN-718) superalloy. Specific shearing energy has been calculated using the dynamic yield strength of IN-718 as obtained by adopting the Johnson–Cook material model. Specific rubbing energy has been estimated using real contact length measured experimentally. Rubbing grit density has been estimated by considering grinding infeed, grit size, wheel structure, and work material hardness unlike the previous models, where it was mostly taken as a constant value. Single grit grinding experiments have been performed with 36 and 20 mesh size single alumina grits to obtain the insight of ductile flow in IN-718 grinding. These experiments have been conducted at grinding speeds of 5, 10, and 15 m/s using vacuum brazed single alumina grit shank fitted into aluminium make dummy grinding wheel. Specific ploughing energy has been estimated after suitably apportioning the tangential forces as obtained from single grit grinding. Two-dimensional study of the scratch profiles has been performed using a compound microscope to investigate plausible ploughing mechanisms of IN-718. The present studies indicate that at lower infeeds, micro-fracturing of alumina grits is more recurrent, whereas wear flattening is more common at higher infeed. The higher pile-up ratio at lower infeed signifies more ploughing resulting into inefficient cutting causing more energy consumption. The micro-fracturing of single alumina grit while scratching has also been observed. The present model for specific grinding energy is an improved version of earlier energy models as it incorporates variables which are much closer to the actual grinding conditions.

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