Application of the Impact Test to Predict Coated Tools' Cutting Performance in Milling Inconel 718

Abstract

Aerospace alloys possess a low machinability and the application of convenient machining conditions, tool and coating materials are of crucial importance for achieving a satisfactory tool life. [1][2][3] Specifically, Inconel 718 has high strength, work hardening and dynamic shear strength at room and elevated temperatures. On the other hand, this important alloy is characterized by low thermal diffusivity in combination with high reaction with tool materials, leading to increased tool cutting loads and temperatures, as well as to extreme abrasion. [4] Traditional material cutting experimentation is usually applied for the evaluation of the coated tool performance. In this paper, a novel methodology is proposed based on innovative analytical and experimental test methods for predicting cutting coated tool efficiency. The PVD films' fatigue strength properties at room and elevated temperatures were detected through impact test investigations. [5a] These results, along with FEM-based calculations of the cutting wedge thermal and mechanical loads during the material removal process, facilitated the explanation of the coated inserts' cutting performance in milling Inconel 718 at various feed rates and cutting speeds and a good correlation was revealed between the impact resistance and the cutting performance at comparable impact or cutting temperature respectively. Coatings and Substrate CharacterizationDetermination of Mechanical Properties Figure 1 illustrates the main elastoplastic specifications of the applied coatings as well as the corresponding substrate data. The TINALOX film is a TiAlN coating deposited by the High Ionization Sputtering (H.I.S.) technique with an Al/Ti content of 54/46 %. [5b] The supernitride SN 2 coating is a TiAlN film too, manufactured by an enhanced plasmaboosted H.I.S. procedure, leading to a nanostructure lattice with almost the same Al/Ti ratio of 53/47 %. [5b] The TiN/ TiAlN film consists of a nanostructured SN 2 coating, covered by a superficial thin (ca. 1 lm) TiN layer. The mechanical properties of the applied coating and substrate materials were detected by nanoindentations and a FEM-based algorithm, facilitating the determination of related stress-strain curves. [7] The SN 2 film possesses superior yield (S Y ) and rupture (S M ) stresses to the rest coatings, whereas as representative mechanical strength properties of the TiN/TiAlN film were considered the corresponding ones of the SN 2 coating, due to the premature failure of the superficial TiN layer during the cutting investigations or the impact tests. Impact Resistance at Room and Elevated TemperaturesThe fatigue strength of the applied coatings was investigated by the impact test at operational temperatures up to COMMUNICATIONS 634 [**] The presented results were conducted in the frame of the European CRAFT project, entitled: "Innovative PVD nanocoatings on tools for machining titanium and nickel alloys (MATINA)", 2005-2007.Fig. 1. Elastoplastic properties of the applied coatings and substrate.

New Methods for Characterizing Coating Properties at Ambient and Elevated Temperatures

“…Additionally, the film yield stress and the rupture stress course versus the temperature were calculated and are presented in Fig. 2c [5]. According to these results, the film elasticity modulus amounts to 580GPa and remains unaffected by the temperature.…”

Materials, properties, manufacturing methods and cutting performance of innovative ceramic cutting tools − a review

“…Working conditions are affected directly by the temperature; thus Bouzakis et al [134] proposed a methodology based on theoretical and experimental tests to predict the performance of a coated cutting tool. The properties of PVD film, like fatigue strength and impact resistance at room and elevated temperatures with different cutting conditions such as cutting forces and feed were examined.…”

Study on Wear Phenomena in Cases of Cyclic Impact With Micro-Slip

“…This has led to the choice that for many practical impact problems, the conditions are such that the size of the impacted structure (target) in the direction of impact is much larger than the size of the projectile. Applications are in the field of adhesion of the coating layers testing [13][14][15][16]. In terms of the behaviour of the target material in the contact zone, several impact wear mechanisms have been highlighted [17,18].…”