Cutting performance of CBN and diamond tools in dry turning of cemented carbide
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2016-01-01 |
| Journal | Mechanical Engineering Journal |
| Authors | A. Kamaruddin, Akira Hosokawa, Takashi UEDA, Tatsuaki FURUMOTO, Tomohiro KOYANO |
| Institutions | Nagoya University, Kanazawa University |
| Citations | 8 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Diamond Tools for Hard Turning of Cemented Carbide
Section titled âTechnical Documentation & Analysis: Diamond Tools for Hard Turning of Cemented CarbideâThis document analyzes the research on the cutting performance of various diamond and CBN tools in the dry turning of cemented carbides (WC). It highlights the critical role of advanced MPCVD diamond materials, specifically Single Crystal Diamond (SCD) and high-density Polycrystalline Diamond (PCD), in achieving superior wear resistance and stable cutting forces in extreme hard turning applications.
Executive Summary
Section titled âExecutive Summaryâ- Core Achievement: Successful dry hard turning of three grades of cemented carbide (WC, 12% to 25% Co binder content) using advanced diamond tools.
- Material Superiority: Binderless Nano-Polycrystalline Diamond (BL-NPD) exhibited the best overall performance, achieving the lowest flank wear and extremely stable principal cutting forces (40 N) when machining medium-hard carbide (WC-d).
- SCD/CVD-SC Necessity: Single Crystal Diamond (SC) and CVD-SC tools were essential for continuous turning of the hardest carbide grade (WC-t, 12% Co), where conventional PCD and CBN tools failed due to low hardness and chipping.
- Wear Mechanism: The primary wear mechanism was attrition, with the ultra-fine grain structure (0.03-0.05 ”m) of BL-NPD providing superior abrasion resistance compared to larger-grained PCD.
- Thermal Management: Despite high-stress hard turning, the high thermal conductivity ($\lambda$) of the diamond tools (up to 2200 W/(m·K)) kept tool flank temperatures relatively low, below 450°C.
- Surface Finish: Stable finished surfaces were achieved, characterized by clear feed marks, confirming the suitability of binderless diamond tools for precision post-processing of molds and dies.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Cutting Style | Dry Internal Turning | N/A | High-stress machining environment |
| Cutting Speed ($v$) | 40 | m/s | Constant operational parameter |
| Depth of Cut ($d$) | 0.05 | mm | Constant operational parameter |
| Feed Rate ($f$) | 0.1 | mm/rev | Constant operational parameter |
| Max Flank Wear Width ($VB_{max}$) | 300 | ”m | Failure criterion for tool life |
| Max Tool Flank Temperature ($T_f$) | < 450 | °C | Measured on SC/CVD-SC tools |
| SC/CVD-SC Thermal Conductivity ($\lambda$) | 1000 - 2200 | W/(m·K) | Highest conductivity materials tested |
| BL-NPD Vickers Hardness (HV) | 120 - 140 | GPa | Highest hardness material tested |
| WC-t (Hardest Carbide) Hardness (HV) | 13.3 | GPa | Workpiece material (12% Co) |
| Stable Cutting Force (BL-NPD on WC-d) | 40 | N | Extremely stable cutting performance |
| Max Cutting Force (BL-NPD on WC-t) | 220 | N | Force limit before tool failure |
| BL-NPD Grain Size | 0.03 - 0.05 | ”m | Nano-polycrystalline structure |
Key Methodologies
Section titled âKey Methodologiesâ- Workpiece Selection: Three grades of straight tungsten cemented carbide (WC-m, WC-d, WC-t) were prepared, varying in Cobalt (Co) binder content (25%, 20%, and 12% by weight) and corresponding Vickers Hardness (8.2 GPa to 13.3 GPa).
- Tool Material Selection: Seven tool types were tested, including Polycrystalline Cubic Boron Nitride (CBN) and five types of diamond: Polycrystalline Diamond (PCD-a, PCD-b), Binderless Nano-Polycrystalline Diamond (BL-NPD), Single Crystal Diamond (SC), and CVD-grown Single Crystal Diamond (CVD-SC).
- Experimental Setup: Internal turning tests were conducted on a vertical machining center under dry cutting conditions (no cutting fluid).
- Fixed Cutting Parameters: Cutting speed was fixed at $v=40$ m/s, depth of cut ($d$) at 0.05 mm, and feed rate ($f$) at 0.1 mm/rev.
- Performance Monitoring:
- Cutting Force: Measured using a 3-axis piezoelectric dynamometer.
- Tool Wear: Monitored via SEM photographs of the flank face.
- Cutting Temperature: Measured using a compact two-color pyrometer (InAs/InSb detectors) inserted into a hole in the workpiece, detecting infrared radiation from the tool flank face (spectral sensitivities 1-3 ”m and 3-5.5 ”m).
- Test Termination: Experiments were halted when the flank wear width ($VB$) reached 300 ”m or when tool failure (major chipping) occurred.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research clearly demonstrates that successful hard turning of cemented carbides requires diamond materials with exceptional hardness, thermal stability, and controlled grain structure (for PCD). 6CCVD specializes in providing the high-specification MPCVD diamond materials necessary to replicate and advance this cutting-edge research.
Applicable Materials for Hard Turning
Section titled âApplicable Materials for Hard Turningâ| Research Requirement | 6CCVD Material Solution | Key Benefit for Application |
|---|---|---|
| SC/CVD-SC Replication | Optical Grade SCD (Single Crystal Diamond) | Highest purity and thermal conductivity (up to 2200 W/(m·K)) for rapid heat dissipation, minimizing thermal wear and maintaining edge integrity during high-stress turning of WC-t. |
| BL-NPD Replication | Fine-Grain PCD (Polycrystalline Diamond) | Engineered grain sizes (down to sub-micron) to replicate the high abrasion resistance and toughness of the binderless nano-polycrystalline structure, crucial for resisting attrition wear. |
| High Hardness/Toughness | Custom SCD/PCD Thickness | We supply SCD and PCD plates up to 500 ”m thick, ensuring robust tool inserts capable of withstanding the high mechanical shocks and forces (up to 220 N) encountered when cutting hard WC grades. |
| Thermal Stability | Boron-Doped Diamond (BDD) | While not the primary focus, BDD substrates offer tailored electrical and thermal properties for integrated sensor applications, potentially enhancing real-time temperature monitoring systems like the two-color pyrometer used in this study. |
Customization Potential for Tool Fabrication
Section titled âCustomization Potential for Tool FabricationâThe success of diamond tools in this study relies heavily on precise insert geometry and material quality. 6CCVD offers comprehensive customization services to meet the exact specifications required for high-performance hard turning:
- Custom Dimensions: We supply SCD and PCD plates/wafers up to 125 mm in diameter, allowing customers to laser cut or fabricate custom inserts with specific nose radii ($r_e = 0.8$ mm used in the study) and rake angles ($\alpha$).
- Ultra-Precision Polishing: 6CCVD provides polishing services achieving surface roughness $R_a$ < 1 nm for SCD and $R_a$ < 5 nm for inch-size PCD. This is critical for minimizing friction, reducing initial wear, and ensuring the stable finished surface quality observed in the research.
- Metalization Services: We offer in-house metalization (Au, Pt, Pd, Ti, W, Cu) for robust brazing and mounting of diamond inserts onto tool holders, ensuring mechanical stability under the high cutting forces experienced.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team are experts in the material science of diamond wear mechanisms. We can assist engineers and researchers in optimizing material selection for similar Hard Turning and Precision Machining projects. Our support includes:
- Consultation on the optimal diamond grade (SCD purity vs. PCD grain size) based on workpiece binder content (e.g., high Co content vs. low Co content WC).
- Analysis of thermal management requirements, leveraging the high thermal conductivity of MPCVD diamond to mitigate temperature-related wear and chemical reactions.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
This research deals with the hard turning of cemented carbide with CBN and diamond tools, and focuses on the tool performance, mainly tool wear with respect to cutting force and cutting temperature. The internal turning tests without cutting fluid are executed with the vertical machining center. Seven types of tool materials: SC, CVD-SC, two PCDs, BL-NPD (Binderless nano-polycrystalline diamond) and CBN: are selected for cutting three grades of cemented carbides WC having the different Co binder content (12%, 20% and 25%). Attrition has been found to be the main tool wear mechanism for all tools with slight adhesion of the workpiece binder on the tool face. In cutting of softest carbide WC-m (25% Co), the polycrystalline CBN tool has the lowest tool wear than any other PCD tools. In turning of harder carbides WC-d (20% Co) and WC-t (12% Co), both polycrystalline CBN and PCD cannot be used continuously due to their low hardness, and BL-NPD, SC and CVD-SC tools are applicable. And the BL-NPD tool has the best cutting performance with less flank wear. As for WC-d, extremely stable cutting can be done with BL-NPD where the principal cutting force is kept almost constant at 40 N. Only BL-NPD tool can continue to turn the hardest WC-t. In spite of turning hard materials, the tool temperatures measured are relatively low below 450°C due to the high thermal conductivities of tool materials. However, cutting temperature is directly related to the tool wear and cutting force rather than thermal conductivity of tool in turning of WC-m and WC-t.