High speed cutting of Inconel 718 with coated carbide and ceramic inserts

doi:10.1016/S0924-0136(02)00590-3

Journal of Materials Processing Technology

Volume 129, Issues 1–3, 11 October 2002, Pages 127-130

https://doi.org/10.1016/S0924-0136(02)00590-3 Get rights and content

Abstract

The cutting speed as a important factor influences the tool wear and the tool life when cutting nickel-based alloys with carbides and ceramics. For optimizing the cutting speed in the turning of Inconel 718, a series of tool life experiments has been carried out using various coated carbides and ceramics by means of rapid face-turning without coolant. At lower speeds (120 m/min), the tools are prone to depth-of-cut (DOC) notching, with minimal damage to the tool nose. A transition is observed at about 240 m/min, increasing the speed to 300 m/min leading to a reduction in DOC notching and an increase in nose and flank wear. The experiment results show that PVD-coated carbides KC7310 are more suitable for cutting Inconel 718 than CVD-coated carbides KC935, and ceramic inserts of KY2000 with negative rake angle and KY2100 of round type are the best choice for the high speed turning of Inconel 718. Based on the Taylor equation and the minimum production time, the optimum cutting speed was optimized in the cylindrical turning of Inconel 718 for each tested insert.

Introduction

High speed machining (HSM) technology is one of important aspects of advanced manufacturing technology. For a long time, the machining of difficult-to-machine materials has caused urgent problems in aviation and other manufacturing industries. Nickel-based superalloys have been used widely in the aircraft and nuclear industry due to their exceptional thermal resistance and the ability to retain their mechanical properties at elevated temperatures of service environments of over 700 °C [1]. However, they are classified as difficult-to-cut materials due to their high shear strength, work-hardening tendency, highly abrasive carbide particles in the microstructure, strong tendency to weld and form a built-up edge, and low thermal conductivity [2], [3]. They have a tendency to maintain their strength at the high temperature that is generated during machining [4].

The main factors that affect the performance of a cutting tool whilst machining superalloys are [5]: (i) high hardness, (ii) wear resistance, (iii) chemical inertness and (iv) fracture toughness.

Nickel-based superalloys are normally machined with WC–Co grades with cutting speeds in the order of 50 m/min. With the introduction of sialon materials, it is possible to increase the cutting speed by a factor of 5, and more recently silicon carbide whisker-reinforced alumina tools have made it possible to machine at cutting speeds of up to 10 times those used with cemented carbide. Ceramic tools are suitable with regard to the first three properties even at high cutting speeds. However, their fracture toughness is much lower than that of the other widely used tool materials such as high speed steel and carbides [6], [7].

In this paper, the authors have experimented with many inserts such as PVD- and CVD-coated carbide grades and Sialon ceramics of various geometrical shapes. For evaluating the inserts machinability in the high speed cutting of Inconel 718, employing the Taylor equation within certain cutting speeds, high speed cutting experiments of tool life were carried out to establish the models of tool life by means of rapid face-turning test [8].

Section snippets

Experimental

The Inconel 718 workpiece materials used in the experiments were in the hot-forged and annealed condition. The chemical composition of the workpiece material confirms to the following specification (wt.%): 0.08 C, 0.35 Mn, 0.35 Si, 0.60 Ti, 0.80 Al, 1.00 Co, 3.00 Mo, 5.00 Nb, 17.00 Fe, 19.00 Cr, 52.82 Ni. The hardness of the workpiece material was measured and found to be 41 HRC. The material worked was a cylinder with an outer diameter of 290 mm, an inner diameter of 240 mm and a length of

Tool wear mechanisms

In the present experiments, the typical tool wear pattern is shown in Fig. 1. The major tool wear mechanisms were interactions of abrasive wear, adhesion wear, micro-breakout and chipping when cutting Inconel 718. The notch wear is a key wear type of ceramics inserts when machining Inconel 718 at high cutting speed.

The tool wear mechanisms of coated carbide inserts were adhesive, coating peeling and fracturing, but the notching wear of coated carbide was not severe during the experiments. Rapid

Conclusions

The conclusions drawn from the turning of Inconel 718 with silicon nitride-based ceramic; PVD- and CVD-coated carbide inserts are as follows:

1.
Studies on tool wear in HSM. Thorough investigations and studies were made on the tool wear form, wear process and wear mechanism in the high speed cutting of difficult-to-machine materials with ceramic tools and with coated carbides. The major wear mechanisms of nickel-based alloys are interactions of abrasive wear, adhesion wear, micro-breakout and

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High speed cutting of Inconel 718 with coated carbide and ceramic inserts

Abstract

Introduction

Section snippets

Experimental

Tool wear mechanisms

Conclusions

Ann. CIRP

J. Eur. Ceram. Soc.

J. Mater. Process. Technol.

High speed machining of Inconel 718 with ceramic tools

Ann. CIRP

End milling machinability of Inconel 718

J. Eng. Manuf.