Influence of the atmosphere and temperature on the properties of the oxygen-affine bonding system titanium-diamond during sintering

At a Glance

Metadata	Details
Publication Date	2022-04-21
Journal	The International Journal of Advanced Manufacturing Technology
Authors	Berend Denkena, Benjamin Bergmann, Andreas Fromm, Christian Klose, Nils Hansen
Institutions	Leibniz University Hannover
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-Performance Titanium-Diamond Bonding

Reference: Influence of the atmosphere and temperature on the properties of the oxygen-affine bonding system titanium-diamond during sintering (The International Journal of Advanced Manufacturing Technology, 2022)

Executive Summary

This research validates the critical role of controlled atmosphere and temperature in achieving superior mechanical and thermal properties in titanium-diamond abrasive layers, directly impacting tool longevity and performance.

Active Bonding Mechanism: The study confirms the formation of Titanium Carbide (TiC) at the interface between Ti bond material and diamond grains, establishing a strong adhesive bond superior to conventional mechanical bronze bonds.
Atmosphere is Critical: A higher vacuum (lower oxygen partial pressure, $P_{atm,1} \approx 50 \text{ mbar}$) is the most significant factor influencing performance, minimizing Ti oxidation and promoting TiC formation.
Performance Gains: Optimal sintering conditions resulted in a +38% increase in critical bond stress ($\sigma^*$) and a +3.4% increase in thermal conductivity ($\lambda$) compared to high-oxygen conditions.
Thermal Resilience: Diamond grains showed minimal graphitization damage even at high sintering temperatures (up to $1100^\circ\text{C}$) due to the short holding time (300 s).
Material System: The Ti-Diamond composite system offers significantly higher critical bond stresses than traditional copper-tin bonds, leading to improved grain retention and wear resistance in grinding tools.
6CCVD Relevance: The findings underscore the necessity of high-purity, controlled environments—a core capability of 6CCVD’s MPCVD diamond manufacturing—for producing high-performance diamond composites and substrates.

Technical Specifications

The following hard data points were extracted from the mechanical and thermal characterization of the titanium-diamond composite samples:

Parameter	Value	Unit	Context
Optimal Sintering Temperature ($T_s$)	900	°C	Achieved maximum critical bond stress ($\sigma^*$)
High Vacuum Atmosphere ($P_{atm,1}$)	$\approx 50$	mbar	Lowest oxygen content, highest performance
Low Vacuum Atmosphere ($P_{atm,2}$)	$\approx 125$	mbar	Higher oxygen content, reduced performance
Max Critical Bond Stress Improvement	+38	%	Observed at $T_s=900^\circ\text{C}$ under $P_{atm,1}$ (no grain)
Max Thermal Conductivity Improvement	+3.4	%	Observed at $T_s=1000^\circ\text{C}$, $T_a=25^\circ\text{C}$ under $P_{atm,1}$
Sintering Pressure ($P_s$)	3,500	N/cm²	Constant pressure applied during FAST sintering
Sintering Holding Time ($t_s$)	300	s	Duration at peak temperature
Diamond Concentration	25	vol.-%	Used in Ti-Diamond composite samples
Thermal Conductivity ($\lambda$) (Max)	18.8	W/(m·K)	Pure Ti sample, $T_s=1000^\circ\text{C}$, $P_{atm,1}$, $T_a=25^\circ\text{C}$
Porosity ($\Phi$) (Min)	$\le 2.5$	%	Achieved in sintered grinding layers

Key Methodologies

The experimental procedure focused on Field Assisting Sintering Technology (FAST) combined with rigorous mechanical, crystallographic, and thermal characterization to quantify the effects of atmosphere and temperature.

Sample Preparation: Ti powder (75 vol.-%) and blocky diamond grains (D252, 25 vol.-%) were mixed and weighed into HDPE containers.
Sintering Process: Samples were manufactured in graphite molds using a Dr. Fritsch DSP 510 FAST press.
Atmosphere Control: Experiments were conducted in two distinct low-vacuum atmospheres ($P_{atm,1} \approx 50 \text{ mbar}$ and $P_{atm,2} \approx 125 \text{ mbar}$) across three temperatures ($900^\circ\text{C}$, $1000^\circ\text{C}$, $1100^\circ\text{C}$).
Mechanical Testing: A three-point flexural test was performed to determine the maximum force ($F_z$) and calculate the adjusted critical bond stress ($\sigma^*$), accounting for porosity.
Crystallographic Analysis (XRD): X-ray Diffraction (XRD) was used on cross-sections to confirm the formation of Titanium Carbide (TiC) and monitor for potential diamond graphitization (C reflections).
Thermal Characterization (LFA): Laser Flash Analysis (LFA 447) was used to measure thermal diffusivity ($\alpha$), which was then combined with density ($\rho$) and specific heat capacity ($c_p$) to calculate thermal conductivity ($\lambda$).
Microstructural Analysis (SEM/EDS): Scanning Electron Microscopy (SEM) with Energy-Dispersive X-ray Spectroscopy (EDS) mapping was employed to visualize elemental distribution (Ti, C, O) and assess grain retention and oxidation effects.

6CCVD Solutions & Capabilities

The research demonstrates that achieving high-performance diamond abrasive tools relies heavily on precise material composition, high-purity processing, and controlled interfaces—all areas where 6CCVD excels. We are uniquely positioned to supply the materials and customization required to replicate and advance this research into commercial applications.

Applicable Materials

To replicate or extend the high-performance Ti-Diamond composite system, 6CCVD recommends the following materials:

Polycrystalline Diamond (PCD) Plates: Ideal for high-volume abrasive applications like grinding tools. 6CCVD offers PCD plates up to 125mm in diameter and thicknesses up to 500µm, providing large-area substrates for testing active bond layers.
Single Crystal Diamond (SCD) Substrates: For fundamental research requiring ultra-high purity and precise orientation control, 6CCVD can supply SCD wafers (0.1µm to 500µm thick) to study the TiC interface formation without the complexity of grain boundaries.
Custom Diamond Grain Supply: While the paper used D252 blocky grains, 6CCVD can supply diamond materials with specific morphologies and surface treatments optimized for active bonding systems like Ti.

Customization Potential

The success of this research hinges on precise geometry and interface control. 6CCVD offers comprehensive customization services to meet these exacting requirements:

Requirement in Paper	6CCVD Customization Capability	Benefit to Customer
Specific Sample Dimensions (22mm dia, 5mm height)	Custom Dimensions & Laser Cutting: Plates/wafers up to 125mm; substrates up to 10mm thick.	Enables rapid prototyping and scaling of abrasive layer geometries.
Need for Ti-Diamond Interface	Custom Metalization: We offer in-house deposition of Ti, Pt, Au, Pd, W, and Cu.	Allows researchers to test the TiC bonding mechanism directly on high-purity SCD or PCD surfaces.
Low Porosity (Ra < 5nm)	Advanced Polishing: Polishing services achieve Ra < 1nm (SCD) and Ra < 5nm (PCD).	Ensures optimal surface preparation for subsequent bonding or metalization steps, minimizing defects that lead to porosity.
High Purity Processing	MPCVD Expertise: Our growth process inherently operates under highly controlled, high-purity conditions.	Analogous to the high-vacuum requirement ($P_{atm,1}$), ensuring minimal oxygen contamination during material preparation.

Engineering Support

6CCVD’s in-house team of PhD material scientists specializes in the growth and characterization of diamond interfaces. We can assist engineers and scientists with:

Active Bonding System Optimization: Providing consultation on material selection and surface preparation to maximize TiC formation and critical bond stress for superabrasive tool projects.
Thermal Management: Assisting in designing diamond composites that leverage diamond’s superior thermal properties, crucial for high-speed grinding applications where heat dissipation is key.
Material Scaling: Supporting the transition of successful lab-scale Ti-Diamond composite recipes to inch-size PCD plates for commercial manufacturing.

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

View Original Abstract

Abstract Grinding tools can be manufactured from metal, vitrified, and resin bond materials. In combination with superabrasives like diamond grains, metal-bonded tools are used in a wide range of applications. The main advantages of metal over vitrified and resin bonds are high grain retention forces and high thermal conductivity. This paper investigates the influence of the atmosphere and manufacturing parameters such as sintering temperature on the properties of titanium-bonded grinding layers. Titanium is an active bond material, which can increase the retention of diamond grains in metal-bonded grinding layers. This can lead to higher bond stress and, consequently, decreased wear of grinding tools in use when compared to other commonly used bond materials like bronze. The reason for this is the adhesive bond between titanium and diamond due to the formation of carbides in the interface, whereas bronze can only form a mechanical cohesion with diamond grains. However, when using oxygen-affine metals such as titanium, oxidizing effects could limit the strength of the bond due to insufficient adhesion between Ti-powder particles and the prevention of carbide formation. The purpose of this paper is to show the influence of the sintering atmosphere and temperature on the properties of titanium-bonded diamond grinding layers using the mechanical and thermal characterization of specimens. A higher vacuum ( Δp atm = − 75 mbar) reduces the oxidation of titanium particles during sintering, which leads to higher critical bond stress (+ 38% @ T s = 900 °C) and higher thermal conductivity (+ 3.4% @ T s = 1000 °C, T a = 25 °C). X-ray diffraction measurements could show the formation of carbides in the cross-section of specimens, which also has a positive effect on the critical bond stress due to an adhesive bond between titanium and diamond.