Damage critical transformation mechanisms in milling nickel-based superalloy honeycomb composites using different tool structures

Abstract

Nickel-based superalloy honeycomb composite (NBSHC) has been developed into an indispensable material for aerospace and defense industries due to light weight, high temperature resistance and extremely high specific strength. Nevertheless, NBSHC is particularly difficult to machine, combing superalloy with thin-walled structure properties, and is prone to damage such as burr, tearing and core deformation. To realize the efficient and low-damage processing of NBSHC, the different tool structures were used during the milling NBSHC experiments under ice-freeing conditions. The material removal mechanisms of different cutters were revealed based on the micro and macro view, and verified by the experiment results. Then, the cutting force and damage behavior of different tools under different parameters during milling NBSHC process were analyzed. For the first time, the damages critical transformation mechanisms during milling NBSHC process were summarized based on above investigations. Results showed that: Since the contact area between saw blade or disc cutters and NBSHC workpiece was a surface, and the in-plane force was small. The qualities of NBSHC machined by saw blade and disc cutters were excellent. Due to the large in-plane force, discontinuity cutting and tearing from removed material, the quality of NBSHC machined by end-milling cutter was extremely terrible. Large cutting force, large contact volume, frequent impacts induced by discontinuity cutting and tearing from the removed material sharply increased the plastic deformation, thus deteriorating the quality of NBSHC and contributing to the transformation of slight damages into severe damages. This work provided significant theories and guidelines for efficient and low-damage machining of NBSHC in aerospace and defense fields.