# Electrochemical Broaching of Inconel 718 Turbine Mortises

## TL;DR

This paper introduces electrochemical broaching as a cost-effective method for manufacturing turbine mortises in Inconel 718, avoiding tool wear and achieving high precision.

## Contribution

The study presents a material dissolution mechanism model and optimal parameters for electrochemical broaching of Inconel 718 turbine mortises.

## Key findings

- Five distinct dissolution states were identified during the electrochemical broaching process.
- Fir-tree turbine mortises were fabricated with dimensional deviations of (+16 to −21) μm and surface roughness of Ra 0.275 μm.
- The tool cathode showed no wear after repeated use, demonstrating the method's efficiency.

## Abstract

The turbine mortise is a critical structural feature of turbine disks, and its manufacturing quality directly determines the performance and service life of aircraft engines. With the increasing application of advanced nickel-based superalloys, severe tool wear in conventional mechanical broaching of turbine mortises has emerged as a key limitation, substantially elevating production costs. Electrochemical broaching (ECB), which removes material through anodic dissolution reactions, eliminates tool wear and thus offers low cost and efficiency advantages, making it a promising method for turbine mortise fabrication. In this study, COMSOL Multiphysics 6.2 was employed to simulate the multiphysics field comprising the electric field, flow field, temperature field, bubble ratio, and dynamic mesh and elucidate the evolution of the electric field during the ECB process. ECB experiments of specimens on Inconel 718 were conducted under different feed speeds. On this basis, optimal processing parameters were identified. The results of the mid-position ECB experiments revealed five distinct dissolution states: pre-processing, pre-transition, stable dissolution, post-transition, and post-processing stages. A material dissolution mechanism model for the ECB process was established. Finally, fir-tree turbine mortises were successfully manufactured on Inconel 718 using a self-developed specialized electrochemical machining system at a feed speed of 70 mm/min. The mortise profile demonstrated dimensional deviations of (+16 to −21) μm, with working surface variations maintained within ±5 μm. The machined surfaces exhibited uniform and dense morphology with a surface roughness of Ra 0.275 μm. Three sets of mortise specimens processed under identical parameters showed excellent consistency, presenting a maximum deviation in profile removal thickness of +4.1 μm. The tool cathode was repeatedly reused without any detectable wear.