Best Materials for CNC Parts: Aerospace Grade

1 Introduction

1.1 Background
High-performance CNC parts in aerospace applications require materials that combine low weight, high strength, and thermal stability. Aluminum, titanium, and nickel-based superalloys are predominant due to their favorable mechanical and chemical properties. Previous studies have compared individual alloys under specific conditions; however, systematic cross-material evaluation under standardized CNC protocols remains limited.

1.2 Objective
This study aims to provide an empirical comparison of aerospace-grade materials based on machinability, mechanical performance, and surface integrity to support informed material selection for CNC-fabricated aerospace components.

2 Methodology

2.1 Material Selection
Three widely used aerospace-grade materials were selected:

• Aluminum 7075-T6

• Titanium Ti-6Al-4V

• Inconel 718

2.2 Experimental Design
CNC milling trials were conducted on a 5-axis machine (DMG Mori DMU 50). Cutting parameters were optimized according to each material’s recommended feed rate and spindle speed. Tool wear was monitored using optical microscopy at 50-hour intervals.

2.3 Mechanical Testing

• Tensile strength measured according to ASTM E8/E8M

• Fatigue life assessed using a rotating bending test

• Hardness measured via Vickers hardness test (HV10)
  Surface roughness (Ra) was measured using a contact profilometer.

2.4 Data Analysis
Comparative analysis included statistical evaluation of mechanical property means, standard deviations, and correlation between machinability indicators and surface integrity.

3 Results and Analysis

3.1 Machinability
Table 1 summarizes tool wear rates and surface roughness. Aluminum 7075 showed minimal tool wear and Ra < 0.8 μm. Ti-6Al-4V required coated carbide tools and demonstrated higher wear (20% increase) with Ra ≈ 1.2 μm. Inconel 718 exhibited the highest wear rates and thermal tool degradation.

Table 1. Machining Performance Metrics

3.2 Mechanical Properties
Figure 1 shows tensile strength versus material type. Ti-6Al-4V reached 950 MPa, exceeding aluminum (570 MPa) but lower than Inconel (1,100 MPa). Fatigue life followed similar trends, with aluminum demonstrating highest cycle counts under low-load conditions, while Inconel excelled under high-load regimes.

Figure 1. Tensile Strength Comparison of Aerospace Materials

3.3 Comparative Insights

• Aluminum: Optimal for weight-sensitive, moderate-strength applications

• Titanium: Best for high-temperature, high-strength environments

• Inconel: Preferred for extreme-load, high-corrosion applications

4 Discussion

4.1 Interpretation of Results
The results confirm that material selection entails a trade-off between machinability and mechanical performance. Aluminum alloys provide efficient machining but limited high-temperature capability. Titanium alloys require specialized tooling, increasing manufacturing complexity. Nickel-based superalloys demonstrate superior endurance but at the cost of higher machining time and tool wear.

4.2 Limitations
This study focuses on standardized CNC milling conditions. Additive manufacturing or alternative cutting strategies may alter comparative performance. Environmental factors such as thermal cycling were not included.

4.3 Practical Implications
Design engineers can apply these findings to optimize material choice based on component function, machining resources, and lifecycle requirements.

5 Conclusion

The study presents a systematic evaluation of aerospace-grade materials for CNC machining. Aluminum 7075 provides high machinability and weight efficiency. Titanium Ti-6Al-4V ensures strength and temperature stability. Inconel 718 delivers corrosion resistance and high-load endurance. These insights support informed material selection for precision aerospace components and guide future research in hybrid manufacturing and advanced tooling strategies.