Machinability and ANN based prediction of surface roughness for TiAlN and PCD coated end mill cutters on AA6061 hybrid composite

At a Glance

Metadata	Details
Publication Date	2025-08-26
Journal	Scientific Reports
Authors	P. Haja Syeddu Masooth, V. Jayakumar, M. Kamatchi Hariharan, M. Satthiyaraju, M. Sathish Kumar
Institutions	SRM Institute of Science and Technology, Amrita Vishwa Vidyapeetham
Analysis	Full AI Review Included

Technical Documentation & Analysis: MPCVD Diamond for High-Performance Milling

Executive Summary

This research validates the superior performance of Polycrystalline Diamond (PCD) coatings in the high-speed milling of challenging AA6061-C-ZrO₂ hybrid composites. The key findings directly support the adoption of high-quality MPCVD diamond materials for advanced manufacturing applications requiring exceptional wear resistance and surface finish.

PCD Superiority: PCD coated end mills delivered the finest surface finish (Rₐ 0.11 to 0.4 µm), significantly outperforming TiAlN-coated (Rₐ 0.3-0.55 µm) and uncoated carbide tools (Rₐ 0.7-7.8 µm).
Stable Machining: The superior thermal conductivity and inherent wear resistance of PCD resulted in minimal tool wear, stable cutting performance, and optimal chip morphology (highest width-to-thickness ratio).
Application Validation: The study confirms that diamond coatings are essential for achieving high surface quality and extended tool lifespan when machining tough, ceramic-reinforced metal matrix composites.
Material Requirement: The experiment utilized PCD coatings (2 µm thickness) on 8 mm carbide end mills, demonstrating the viability of thin diamond layers for extreme conditions.
Predictive Modeling: An Artificial Neural Network (ANN) model successfully predicted surface roughness with high accuracy, achieving a Regression coefficient (R²) of up to 0.9838 for the TiAlN tool and 0.9699 for the PCD tool.
Optimization: Optimal parameters for minimizing surface roughness using PCD were identified as low Spindle Speed (3000 rpm), low Depth of Cut (0.5 mm), and high Feed Rate (300 mm/min).

Technical Specifications

Parameter	Value	Unit	Context
Workpiece Composition	90% AA6061, 5% C, 5% ZrO₂	%	Hybrid composite
Tool Diameter	8	mm	Carbide end mill substrate
PCD Coating Thickness	2	µm	Applied via PVD method
Spindle Speed (SS) Range	3000, 4000, 5000	rpm	Input factor
Depth of Cut (DoC) Range	0.5, 1, 1.5	mm	Input factor
Feed Rate (FR) Range	100, 200, 300	mm/min	Input factor
Best Surface Roughness (PCD)	0.11 to 0.4	µm	Achieved across 9 trials
Worst Surface Roughness (UCC)	7.8487	µm	Uncoated carbide tool (Trial 4)
Optimal PCD Rₐ Setting	3000 SS, 0.5 DoC, 300 FR	rpm, mm, mm/min	Taguchi optimized setting
ANN Prediction Accuracy (R²)	0.9838	N/A	Highest R² value for TiAlN Rₐ prediction
ANN Prediction Accuracy (R²)	0.9603	N/A	Highest R² value for PCD w/t ratio prediction

Key Methodologies

The experiment utilized a systematic approach combining material fabrication, controlled CNC milling, Taguchi optimization, and advanced machine learning modeling.

Workpiece Fabrication: The AA6061/Graphite/ZrO₂ hybrid composite was fabricated using the stir casting method to ensure uniform reinforcement dispersion.
Tool Preparation: Three types of 8 mm carbide end mills were used: Uncoated Carbide (UCC), TiAlN coated, and Polycrystalline Diamond (PCD) coated.
Coating Application: The TiAlN and PCD coatings were applied to the carbide substrates using the Physical Vapor Deposition (PVD) method to a thickness of 2 µm.
Experimental Design: The milling trials were designed using a Taguchi L₉ orthogonal array to efficiently test three input factors (SS, DoC, FR) at three levels each.
Machining Conditions: All milling operations were processed under dry conditions on a CNC milling machine.
Response Measurement: Surface roughness (Rₐ) was measured using a Surfcom 1400G machine. Chip morphology (width-to-thickness ratio) was measured using an Optical Length Measurement (OLM) vision system.
Predictive Modeling: An Artificial Neural Network (ANN) model, featuring a multilayer feed-forward architecture with ReLU activation functions, was developed and trained to predict Rₐ and cylindricity error based on input parameters.

6CCVD Solutions & Capabilities

The research clearly demonstrates that high-quality diamond coatings are essential for the efficient and precise machining of advanced metal matrix composites (MMCs). 6CCVD, as an expert supplier of MPCVD diamond, offers materials and customization capabilities that exceed the requirements of this study, enabling researchers and engineers to replicate and advance this high-performance milling application.

Applicable Materials

The study utilized PVD-coated PCD. 6CCVD specializes in MPCVD Polycrystalline Diamond (PCD), which offers significant advantages over PVD coatings, including superior purity, enhanced thermal stability, and better adhesion, making it the ideal choice for extreme wear applications like ZrO₂-reinforced composite milling.

6CCVD Material Recommendation	Key Benefit for This Application
High-Purity MPCVD PCD Wafers	Superior wear resistance and thermal conductivity, directly addressing the high temperatures and friction encountered when milling MMCs.
Thick PCD Substrates (up to 500 µm)	Allows for the fabrication of robust, brazable diamond inserts with extended tool life compared to thin PVD coatings (2 µm used in the study).
Optical Grade SCD	For ultra-precision finishing applications where Rₐ < 1 nm is required, offering the highest possible material quality and thermal management.

Customization Potential

6CCVD’s in-house capabilities ensure that the material specifications can be perfectly tailored to the demands of high-performance cutting tool fabrication.

Research Requirement	6CCVD Customization Capability
Tool Dimensions	We supply PCD plates/wafers up to 125 mm in diameter, suitable for manufacturing large diamond inserts or complex geometries.
Coating/Insert Thickness	We offer PCD material thicknesses from 0.1 µm up to 500 µm, providing flexibility for thin coatings or thick, self-supporting inserts (the study used 2 µm).
Surface Finish	Our standard polishing achieves Rₐ < 5 nm for inch-size PCD, ensuring the lowest possible friction and optimal chip evacuation—a critical factor identified in the research.
Tool Integration	We offer internal metalization services (Au, Pt, Pd, Ti, W, Cu) necessary for brazing PCD inserts securely onto carbide shanks, ensuring structural integrity during high-speed machining.

Engineering Support

The successful milling of AA6061-C-ZrO₂ composites requires precise material selection to manage the high hardness of the ZrO₂ reinforcement. 6CCVD’s in-house PhD team provides expert consultation to assist engineers and scientists in:

Selecting the optimal diamond grain size and thickness for specific material removal rates (MRR) and surface finish targets.
Designing custom metalization schemes for robust tool bonding and thermal management.
Integrating diamond materials into complex tool geometries for similar high-speed composite milling projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

Tech Support

Original Source

DOI: https://doi.org/10.1038/s41598-025-17489-x