Material Removal Mechanisms of Polycrystalline Silicon Carbide Ceramic Cut by a Diamond Wire Saw

At a Glance

Metadata	Details
Publication Date	2024-08-27
Journal	Materials
Authors	Huyi Yang, Ming Fu, Xin Zhang, Kailin Zhu, Lei Cao
Institutions	Southwest Jiaotong University, China General Nuclear Power Corporation (China)
Citations	3
Analysis	Full AI Review Included

Executive Summary

This research investigates the material removal mechanisms of polycrystalline Silicon Carbide (SiC) ceramic during high-speed diamond wire sawing (DWS), focusing on optimizing efficiency and surface quality.

High-Efficiency Parameters: Experiments utilized high wire speeds (30 m/s) and high feed rates (up to 2.0 mm/min), significantly exceeding typical literature values, to push the limits of SiC processing efficiency.
Composite Removal Mechanism: The material removal is a composite process involving both plastic deformation and brittle fracture. Plastic mechanisms include dislocation generation, amorphization, and stacking fault formation within the grains, confirmed via FIB-TEM analysis.
Abrasive Wear Impact: The morphology of the fixed-plated diamond abrasives changes significantly during grinding, transitioning from sharp protrusions to flattened grits. This wear dynamically alters the removal ratio, reducing plastic deformation and increasing the dominance of brittle fracture.
Feed Rate vs. Quality Trade-off: Surface roughness (R_a) remains stable at low feed rates (up to 0.5 mm/min) but increases rapidly at higher rates (up to 3.8 µm at 2.0 mm/min). This threshold indicates where brittle fracture becomes the overwhelmingly dominant removal mode, degrading surface quality.
Material Structure: The SiC ceramic tested was highly pure, consisting primarily of the 6H-SiC polytype (approx. 94.23%), which governs the material’s mechanical response during grinding.
Internal Damage Confirmation: TEM analysis revealed internal stress distribution (alternating light/dark stripes) extending across grain boundaries and confirmed the presence of microcracks, dislocation lines, and amorphous regions originating from the grinding surface.

Technical Specifications

Parameter	Value	Unit	Context
SiC Composition	94.23	%	Main phase is 6H-SiC
Vickers Hardness (H_v)	23	GPa	Mechanical property of SiC ceramic
Young’s Modulus (E)	405	GPa	Mechanical property of SiC ceramic
Fracture Toughness (K_Ic)	2.9	MPa·m^1/2	Mechanical property of SiC ceramic
Density	3.1	g/cm³	Material property
Sintering Temperature	1850	°C	Hot press sintering condition
Sintering Pressure	30	MPa	Hot press sintering condition (in Argon)
Diamond Wire Speed	30	m/s	Fixed reciprocating grinding condition
Feed Rate Range (Tested)	0.25 to 2.0	mm/min	Variable grinding condition
Diamond Wire Diameter	0.38	mm	Iron-based alloy core, fixed-plated diamond
Surface Roughness (R_a) Range	2.8 to 3.8	µm	Measured roughness corresponding to feed rate increase
TEM Sample Thickness	30	nm	Prepared using Focused Ion Beam (FIB)

Key Methodologies

The polycrystalline SiC ceramic was synthesized and then subjected to high-speed diamond wire sawing (DWS) followed by multi-scale characterization.

SiC Synthesis:
- SiC powders were dry-milled for 10 hours using agate balls to ensure uniform particle distribution.
- The powder was hot-pressed (ZT-40-21YT) at 1850 °C under 30 MPa pressure for 2 hours in an argon atmosphere.
Diamond Wire Sawing (DWS):
- A diamond wire-cutting machine (SH280YX) was used with a reciprocating grinding method.
- The abrasive tool was a fixed-plated diamond wire (0.38 mm diameter, iron-based alloy core).
- Process Parameters: Wire speed was fixed at 30 m/s. Feed rates were varied at 0.25, 0.5, 1.0, and 2.0 mm/min.
- Cooling: A water-based coolant was continuously sprayed onto the grinding area.
Surface and Abrasive Characterization:
- Phase Analysis: X-ray diffraction (XRD) confirmed the material composition (predominantly 6H-SiC).
- Morphology and Wear: Field Emission Scanning Electron Microscopy (FE-SEM) was used to observe the wear of the diamond wire (new vs. used) and the surface characteristics (plow marks, fracture).
- Roughness Measurement: Laser Confocal Microscopy (VK-9700) provided 3D topography and quantitative roughness data (R_a and R_z).
Subsurface Mechanism Analysis (FIB-TEM):
- Sample Preparation: Focused Ion Beam (FIB) technology was used to prepare ultra-thin cross-section lamellae (30 nm thickness) perpendicular to the grinding trace.
- Microstructure Analysis: Transmission Electron Microscopy (TEM) and High-Resolution TEM (HRTEM) were employed to analyze internal defects, including:
  - Dislocation lines and internal stress distribution.
  - Microcrack formation and propagation.
  - Amorphization (confirmed by Fast Fourier Transform (FFT) analysis of non-periodic regions).
  - Stacking faults (confirmed by reciprocal rods in SAED patterns).

Commercial Applications

The findings directly support the optimization of manufacturing processes for high-performance SiC components, particularly in industries requiring high material removal rates and stringent surface integrity.

Semiconductor and Electronics: High-efficiency slicing of SiC wafers for power electronics (e.g., MOSFETs, diodes) and high-frequency devices, where minimizing subsurface damage is critical for device performance.
Aerospace and Defense: Manufacturing of SiC components requiring high strength, low thermal expansion, and superior tribological properties, such as structural parts and high-temperature sensors.
Automotive Industry: Production of SiC components for electric vehicle (EV) power systems and high-wear parts due to SiC’s excellent corrosion and wear resistance.
Advanced Materials Processing: General application of diamond wire sawing for efficient cutting of other brittle materials, crystals, and structural ceramics (e.g., Si₃N₄, Al₂O₃).
Precision Engineering: Improving grinding techniques to achieve a better balance between material removal rate and surface quality for high-precision optical and mechanical components.

View Original Abstract

Polycrystalline silicon carbide (SiC) is a highly valuable material with crucial applications across various industries. Despite its benefits, processing this brittle material efficiently and with high quality presents significant challenges. A thorough understanding of the mechanisms involved in processing and removing SiC is essential for optimizing its production. In this study, we investigated the sawing characteristics and material removal mechanisms of polycrystalline silicon carbide (SiC) ceramic using a diamond wire saw. Experiments were conducted with high wire speeds of 30 m/s and a maximum feed rate of 2.0 mm/min. The coarseness value (Ra) increased slightly with the feed rate. Changes in the diamond wire during the grinding process and their effects on the grinding surface were analyzed using scanning electron microscopy (SEM), laser confocal microscopy, and focused ion beam (FIB)-transmission electron microscopy (TEM). The findings provide insights into the grinding mechanisms. The presence of ductile grinding zones and brittle fracture areas on the ground surface reveals that external forces induce dislocation and amorphization within the grain structure, which are key factors in material removal during grinding.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma17174238

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