Grain flash temperatures in diamond wire sawing of silicon
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-06-11 |
| Journal | The International Journal of Advanced Manufacturing Technology |
| Authors | Uygar Pala, Stefan SĂŒssmaier, Konrad Wegener |
| Institutions | Inspire, ETH Zurich |
| Citations | 9 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Diamond Wire Sawing Thermal Dynamics
Section titled âTechnical Documentation & Analysis: Diamond Wire Sawing Thermal DynamicsâExecutive Summary
Section titled âExecutive SummaryâThis analysis focuses on the thermal characterization of diamond-silicon contact during high-speed scratching, directly relevant to diamond wire sawing (DWS) wear and efficiency. The findings underscore the critical role of diamond material properties and precise geometry control in managing extreme flash temperatures.
- Extreme Thermal Environment: Flash temperatures ($T_f$) exceeding 1500 K (and predicted up to 2000 K at low penetration depths) were measured at the diamond grain tip during dry cutting of single-crystal silicon (sc-Si).
- Wear Mechanism Driver: The study confirms that thermal energy dissipation is the primary factor influencing grain wear and workpiece quality in DWS.
- Material Removal Correlation: A strong correlation was established between the material removal mode and temperature: ductile cutting results in significantly higher flash temperatures than brittle fracture.
- Modeling Requirement: Accurate thermal modeling requires high-purity diamond material properties (specifically, high thermal conductivity, $k$) and precise control over the grain-workpiece contact area ($A_L$).
- 6CCVD Value Proposition: 6CCVD provides the necessary high-purity Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) materials, coupled with ultra-precise polishing and custom metalization, essential for replicating or extending this advanced thermal wear research.
- Customization Need: The model required an empirical correction factor (4.5) largely due to geometric simplifications; 6CCVDâs ability to provide custom, highly polished diamond segments minimizes geometric uncertainty for future validation.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results and material property tables, highlighting the extreme conditions encountered at the grain-workpiece interface.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Measured Flash Temperature ($T_f$) | > 1500 | K | Observed during dry cutting (40 mm contact length) |
| Predicted Max Flash Temperature ($T_f$) | > 2000 | K | Predicted at very low penetration depths (< 500 ”m) |
| Cutting Speed ($v_c$) | 10 | m/s | Experimental scratch test velocity |
| Contact Length (Single Pass) | 40 | mm | Emulating long contact lengths in DWS |
| Diamond Thermal Conductivity ($k$) | 2000 - 2100 | Wm-1K-1 | Property of Type IIa Single Crystal Diamond (SCD) |
| Silicon Thermal Conductivity ($k_w$) | 156 | Wm-1K-1 | Property of sc-Si at 300 K |
| Silicon Density ($\rho_w$) | 2329 | kgm-3 | Property of sc-Si at 300 K |
| Workpiece Surface Roughness ($R_z$) | 0.49 - 0.52 | ”m | Mirror-like finish prior to scratching |
| Empirical Correction Factor | 4.5 | - | Required to compensate for model simplifications |
Key Methodologies
Section titled âKey MethodologiesâThe research employed a novel, high-speed single-grain scratch test setup to simulate the thermal conditions of diamond wire sawing.
- Workpiece Preparation: Solar-grade monocrystalline silicon (sc-Si) was prepared with multiple lapping and polishing steps to achieve a mirror-like surface finish ($R_z$ approx. 0.5 ”m).
- Tool Isolation: A commercial diamond wire was fixed to an aluminum pin, and a single abrasive grain (tip radius 0.5 mm) was isolated for testing.
- Kinematics & Environment: Experiments were conducted dry (no coolant) on a 5-axis milling machine, simulating high-speed DWS conditions ($v_c = 10$ m/s) over a long contact length (40 mm per scratch).
- Force and Temperature Measurement: A 3-component force dynamometer measured cutting forces ($F_c$). Flash temperatures ($T_f$) were measured dynamically at the grain tip using a Fire-3 two-color fiber optic pyrometer.
- Geometric Analysis: Optical measurement (Alicona IFM) was used to analyze grain protrusion ($h_g$), penetration depth ($h_{cu}$), and the actual grain-workpiece contact area ($A_{cu}$).
- Thermal Modeling: A steady-state heat flow model was derived based on Archard, Carslaw, and Jaeger principles, incorporating the Peclet number ($Pe$) and heat flux distribution between the diamond grain and the silicon workpiece.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research highlights the critical need for high-quality, thermally stable diamond materials and precise geometric controlâcore competencies of 6CCVD. We offer tailored solutions to advance thermal and wear modeling in high-speed machining applications like DWS.
Applicable Materials for Replication and Extension
Section titled âApplicable Materials for Replication and ExtensionâTo accurately model and validate the thermal behavior observed in this study, researchers require diamond materials with certified, high-purity thermal properties, equivalent to the Type IIa SCD referenced in the paper.
| Research Requirement | 6CCVD Material Solution | Technical Advantage |
|---|---|---|
| High Thermal Conductivity | Optical Grade SCD (Type IIa Equivalent) | Thermal conductivity (k) up to 2100 Wm-1K-1 ensures maximum heat dissipation, crucial for accurate $T_f$ modeling and minimizing grain degradation. |
| Large Abrasive Segments | High-Purity PCD Plates (up to 125mm) | Available in thicknesses from 0.1 ”m to 500 ”m, ideal for creating large, stable abrasive segments for advanced scratch testing rigs or simulating fixed-abrasive tools. |
| Wear-Resistant Substrates | SCD Substrates (up to 10mm thickness) | Provides robust, thermally stable platforms for brazing or mounting custom abrasive geometries, ensuring experimental stability at high speeds and temperatures. |
Customization Potential for Enhanced Model Accuracy
Section titled âCustomization Potential for Enhanced Model AccuracyâThe paper noted that geometric simplifications (specifically, overestimating the contact area $A_L$) necessitated a large empirical correction factor (4.5). 6CCVDâs precision engineering capabilities directly address this limitation.
- Ultra-Precision Polishing: We offer SCD polishing to Ra < 1 nm and inch-size PCD polishing to Ra < 5 nm. Providing grains or segments with highly controlled, known geometries (e.g., specific tip radii or defined cutting edges) minimizes the geometric uncertainty ($A_{cu}$ vs. $A_L$) that plagued the current model validation.
- Custom Dimensions and Thickness: We supply plates and wafers up to 125 mm (PCD) and SCD up to 500 ”m thick, allowing researchers to design custom abrasive tools optimized for specific penetration depths ($h_{cu}$) and contact lengths.
- Advanced Metalization Services: For researchers developing brazed diamond tools (as opposed to electroplated wire), 6CCVD offers in-house metalization capabilities (Au, Pt, Pd, Ti, W, Cu). This ensures strong, thermally conductive bonding to the pin or substrate, improving the accuracy of the heat flow assumption to the bonding material ($T_b$).
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists specializes in the thermal, mechanical, and electronic properties of CVD diamond. We can assist researchers in:
- Material Selection: Optimizing diamond grade (SCD vs. PCD) and doping (BDD) based on specific thermal load, cutting speed, and workpiece material requirements.
- Thermal Modeling Consultation: Providing certified material property data (density, specific heat, thermal conductivity) necessary for refining the flash temperature model (Eq. 11) and reducing reliance on empirical factors.
- Custom Tool Design: Engineering diamond segments with precise geometries and metal layers for next-generation, high-fidelity scratch testing setups aimed at wear and thermal analysis in DWS projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Diamond wire sawing has obtained 90% of the single-crystal silicon-based photovoltaic market, mainly for its high production efficiency, high wafer quality, and low tool wear. The diamond wire wear is strongly influenced by the temperatures in the grain-workpiece contact zone; and yet, research studies on experimental investigations and modeling are currently lacking. In this direction, a temperature model is developed for the evaluation of the flash temperatures at the grain tip with respect to the grain penetration depth. An experimental single-grain scratch test setup is designed to validate the model that can emulate the long contact lengths as in the wire sawing process, at high speeds. Furthermore, the influence of brittle and ductile material removal modes on cutting zone temperatures is evaluated.