Retificabilidade das ligas de níquel Inconel 625 e Inconel 718

Abstract

Nickel-based superalloys are classified as difficult-to-cut materials. This difficulty becomes worse when these materials are processed by grinding, thus requiring more attention in the selection of proper grinding parameters. Among the nickel-based superalloys, the Inconel 718 is the most used alloy, however, the Inconel 625 alloy is also important because of its peculiar properties such as resistance to aqueous and hot corrosions, high strength and resistance to creep. In this sense and motivated by the lack of information about grinding of Inconel 625 alloy, this work evaluates the grindability of this superalloy and compares to the Inconel 718, in several operational conditions. The tests were divided in two stages. In the first stage, the effect of the main input parameters (depth of cut – ae, workspeed – vw, cutting speed – vs, grinding wheel mesh and grinding direction) was evaluated for the Inconel 625 based on surface roughness (Ra and Rz), grinding forces and specific energy in order to determine the statistically significant parameters and then use them for the tests for the evaluation of the grindability of the Inconel 625 and Inconel 718 (second stage). In this stage the ae, vw, vs and grinding wheel mesh were varied. The output parameters used to assess the grindability were the surface roughness (Ra and Rz), images of the ground surfaces obtained by scanning electron microscopy (SEM), microhardness on the surface and below it, grinding forces, specific energy and temperature in the grinding zone. In general, the results showed that the Inconel 625 is harder to grind than the Inconel 718. The surface roughness (Ra and Rz) obtained for Inconel 625 workpieces were higher than those obtained for Inconel 718 for all analyzed conditions. With the higher cutting speed, SEM images indicated a greater presence of plastic deformations on the Inconel 625 surfaces, which led to its work hardening, increasing the microhardness. Grinding forces and specific energy were slightly higher for Inconel 718, while the temperature in the grinding zone was higher for Inconel 625 when compared to Inconel 718.