Experimental Analysis of Milling of Inconel 600 Using Vegetable-Based Cutting Oil with Boric Acid Nano Additives

Abstract

Inconel 600 is a nickel-chromium alloy, which is suitable for high corrosion and heat resistance applications. This nickel-chromium alloy has outstanding mechanical properties and composes the best workability and high strength combination. Usage of super alloys like Inconel 600 has become a trend nowadays due to the high strength attained with the production of low-weight products. At present days, mostly mineral oils are used while machining to reduce the temperature of the work piece-tool interface. Whereas, the usage of mineral oils causes damage to operators as well as the environment. This mineral oil when exited into the environment it does not get decomposed easily. It also causes respiratory problems to the operators. So, vegetable-based cutting oil can be replaced instead of mineral oil. The present paper deals with such vegetable-based cutting oil and is used for milling Inconel 600 superalloy. Milling experiments were carried out with PVD TiAlN coated carbide inserts in a CNC milling machine. The experiments were conducted with varying speed (1200, 1400, 1600 rpm), feed rate (100, 130, 150 mm/min) and depth of cut (0.15, 0.20, 0.25 mm). Three conditions (dry, wet, wet with additives) were employed. So, a total of 27 experiments were performed. Tool wear and surface roughness were compared for the three conditions. For finding the optimum milling condition Taguchi optimization technique was employed. The vegetable-based cutting oil was added with 1 wt. % boric acid nanoparticles. Tool wear was found best optimal for wet with additives along with 1200 rpm, 100 mm/min, 0.15mm condition. Surface roughness was best suited for wet with additives along with 1400 rpm, 130 mm/min, and 0.20 mm conditions. So, adding nano-additives with coconut oil was found useful as a cutting oil for milling Inconel 600.

Introduction

This study investigates the machinability of Inconel 600, a nickel-chromium-based superalloy known for its high strength, corrosion resistance, and thermal stability but also for its poor machinability due to high tool wear, built-up edge (BUE), and heat generation. To address these challenges, the research explores the use of vegetable-based nanofluids—specifically coconut oil with 1% boric acid nanoparticles—as an eco-friendly coolant/lubricant during milling.

Key Highlights:

1. Problem Background:

• Inconel 600 is widely used in high-temperature applications (jet engines, heaters, etc.).

• Its poor machinability leads to high tool wear, heat generation, and BUE.

• Dry milling and even traditional wet methods are often inadequate.

• Vegetable oils, especially with nano-additives, offer a greener alternative to mineral-based cutting fluids.

2. Experimental Methodology:

• Workpiece: Inconel 600 block (75×75×30 mm).

• Tool: TiAlN-coated carbide inserts.

• Coolant Types:
  a. Dry (no coolant)
  b. Wet (coconut oil)
  c. Wet with 1% boric acid nano-additive in coconut oil

• Nanofluid Preparation: Boric acid nanoparticles were ultrasonically mixed with coconut oil.

• Experimental Design:

  • Taguchi L9 orthogonal array (9 test combinations)

  • Parameters varied: spindle speed, feed rate, and depth of cut

  • Measured outputs: Surface Roughness (Ra) and Tool Wear

3. Results:

A. Surface Roughness (Ra):

• Lowest Ra (0.214 µm) was achieved using coconut oil + boric acid in Experiment 5 (1400 rpm, 130 mm/min, 0.20 mm).

• Dry milling consistently resulted in higher Ra, especially at high feed and depth of cut.

• Nano-additive fluid consistently outperformed both dry and pure oil in surface finish.

B. Tool Wear:

• Lowest tool wear (0.0286 mm) occurred under wet with additives in Experiment 1 (lowest cutting parameters).

• Dry milling showed the highest tool wear, especially at higher parameter settings.

• Coconut oil with boric acid reduced wear across all conditions due to improved lubrication.

Conclusion

In this work, Inconel 600 was machined with vegetable-based cutting oil along with nanoparticle (Boric acid) additives. The additives were mixed with the vegetable oil in 1 wt.% concentration. The additive was made to nanoparticle size using Particle Sieve and was mixed using Ultrasonicator and Magnetic Stirrer. The experiments were deliberatively conducted with Taguchi\'s L9 orthogonal array. The machining parameters such as spindle speed, feed, depth of cut, and responses like surface roughness and flank wear were considered. The S/N ratio for the design parameters was obtained from Minitab software and the graph was plotted. All the experiments were conducted at room temperature. From the experimental results, the following conclusions have arrived: 1) The Surface Roughness was influenced by cutting fluid and additives. 2) The Tool Wear was also influenced by the design parameters and cutting fluids. 3) For obtaining the lowest Surface Roughness coconut oil with 1 wt. % boric acid with 1400 rpm, 130 mm/min, and 0.20 mm design parameters can be used. 4) For obtaining the lowest Tool Wear vegetable oil with additives with low design parameters can be used. 5) Using vegetable oil and adding nanoparticle additives was found to be useful and showed better results.

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Copyright © 2025 Raghul Anandh K S, V. Hariharan . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.