# Tribological Behavior and Material Removal Mechanisms in Sapphire Lapping Using HFCVD Diamond-Coated Tools

## TL;DR

This study examines how different diamond coatings affect sapphire lapping, finding that specific textures improve surface finish and material removal rates.

## Contribution

The novel use of HFCVD diamond-coated tools with distinct surface textures for sapphire lapping and the establishment of material removal models based on morphology.

## Key findings

- Spherical diamond coatings produce the best surface finish (Ra 0.22 μm) due to continuous multi-point contact.
- Sample 3 achieved the highest removal rate of 24.3 μm/min due to its morphology and two-body contact mechanism.

## Abstract

Diamond coatings with three distinct surface textures, namely spherical, pyramidal, and prismatic morphologies, were fabricated using the hot-filament chemical-vapor deposition (HFCVD) method. Scanning electron microscopy (SEM) was employed to analyze the surface morphological characteristics and differences among the coatings. Raman spectroscopic analysis further confirmed that all three diamond films exhibited excellent deposition uniformity and high crystalline quality. A three-dimensional optical microscopy system was used to measure the surface roughness values, which were determined to be Ra 0.423 μm, Ra 0.515 μm, and Ra 0.809 μm, respectively. An HFCVD diamond-coated tool was innovatively employed for the lapping of sapphire wafers, enabling a systematic investigation of the tribological behavior during the lapping process. Based on the experimental results, three morphological material removal models were established. The study demonstrates that the spherical diamond coating achieves a superior surface finish (Ra 0.22 μm) due to its continuous multi-point contact geometry, governed by the agglomerated nanocrystalline structure. Sample 3 had the highest removal rate of 24.3 μm/min. This is related to its surface morphology characteristics and is also due to the two-body contact between the diamond-coated tool and sapphire, offering a high-efficiency alternative for precision machining.