Search Results (4)

The large aspect ratio micro end mill is a critical tool for microstructure machining, and its performance directly determines processing quality and efficiency. Diamond coatings are commonly applied to cutting edges to enhance wear resistance and extend tool life. However, existing coating techniques often suffer from poor uniformity and inadequate consistency, limiting batch production and process stability. Aerosol jet printing (AJP) offers a cost-effective and highly controllable alternative for the efficient, large-scale deposition of diamond coatings on micro end mills, where precise control of line spacing is essential to achieving coating uniformity. In this study, a transient numerical model of droplet deposition in AJP is developed using computational fluid dynamics (CFD). The volume of fluid (VOF) method and the discrete phase model (DPM) are coupled to track liquid–gas interface deformation and diamond particle motion, enabling the dynamic evolution of droplet deposition to be captured. The effects of inter-droplet distance on deposition, spreading, coalescence, and line uniformity are systematically investigated. Droplet deposition mechanisms are analyzed under low-speed jetting conditions, while high-speed jetting simulations are conducted to reflect industrial processing scenarios. The results show that under low-speed jetting, droplets undergo spreading, contraction, and rebound, eventually forming a uniform cap-like structure. Under high-speed jetting, droplets exhibit a dispersed ring-shaped spreading pattern; although uniformity is slightly reduced, the spreading area and deposition efficiency are significantly increased. These findings provide a theoretical basis for optimizing AJP process parameters to achieve high-quality diamond coatings on micro end mills. Full article

Diamond films deposited on stainless steel using a Cr/CrSiN interlayer exhibit excellent adhesion under static conditions but poor adhesion under scratch conditions. We developed a new interlayer Cr/CrSiVN and investigated the influence of different vanadium (V) contents on the adhesion. The adhesion of diamond films under scratch conditions is significantly improved with V content increasing from 0 to 4.1 at.%. Specifically, the critical load increases from 2.2 ± 0.8 N (0% V) to 21.2 ± 0.8 N (4.1% V), corresponding to a roughly 864% enhancement. High adhesion is ascribed to a certain thickness of carbide, the reduction in pores at the diamond/interlayer interface, and the enhanced hardness of the CrSiVN interlayer by solid solution strengthening. The formation rate of carbide is reduced due to a low carbon diffusion by the substitution of Cr atoms by V atoms in the interlayer, leading to a low carbonization rate of the interlayer and small pores at the interface. This work is of great significance to the promotion and practical application of diamond films in medical and food-processing equipment. Full article

This study comparatively evaluated Raydent (here interpreted as a standard black chrome-type industrial condition in the present specimen context), DLC, and SiO₂ coatings for high-precision LM-guide applications as an application-oriented initial screening study. The emphasis was placed on dimensional preservation, surface integrity, and mechanical surface response rather than on complete coating-mechanism validation. Cross-sectional FE-SEM, EDS, Vickers hardness testing, surface profilometry, AFM, and SEM analyses were conducted to compare coating thickness, composite surface hardness, roughness, and morphology, and the influence of plasma pretreatment on the SiO₂ system was additionally investigated. Among the investigated coatings, SiO₂ exhibited the smallest thickness (1.03 μm), highest composite surface hardness (719.8 HV), and lowest average roughness (213.5 nm), suggesting favorable dimensional compatibility and surface integrity under the tested conditions. Plasma pretreatment increased the EDS-detected Si signal from 0.77 to 2.81 wt% and improved the composite surface hardness from 580 to 720 HV, suggesting an altered near-surface response and improvement in coating formation during pretreatment-assisted processing. AFM and SEM observations further indicated that the SiO₂ coating provided a more uniform and flatter surface morphology on the coupon specimens, whereas the DLC specimen prepared under the present commercial condition showed localized protrusions that may be associated with initial local contact disturbance. The comparative results suggest that SiO₂ coatings provide a favorable balance of thickness control, surface uniformity, composite surface hardness, and roughness for precision LM-guide applications. Although additional rolling-contact durability, adhesion, wear, friction-coefficient, and rolling-contact-fatigue studies are still required, the present findings should be interpreted as an initial screening result indicating that SiO₂ is a candidate coating condition for further engineering consideration in precision motion-guide systems, rather than as a direct validation of full tribological or long-term durability performance. Full article

Hot-filament chemical vapor deposition (HFCVD) facilitates the realization of industrial mass production owing to its simple synthesis device, facile control of process conditions, and low preparation cost. Reactive pressure is one of the deposition parameters that exert a profound influence on the growth of HFCVD diamond films on polycrystalline diamond (PCD) substrates, primarily affecting the growth rate and grain size of the deposited diamond coating. A univariate experimental approach was employed to investigate the effects of reactive pressure (2 kPa, 3 kPa, 4 kPa, 5 kPa) on the properties of as-deposited diamond films. The results show that with the increase in reactive pressure, the growth rate increased first and then decreased, peaking at 5.366 μm/h at 3 kPa. The fractal dimension and grain size follow a similar variation trend, both decreasing first and then increasing. The grain size drops to 15.8 nm when the reactive pressure is 3 kPa, at which point the adhesive strength of the film is maximized. This phenomenon can be attributed to the fact that excessively low reactive pressure extends the mean free path of particles and active species, endowing them with higher kinetic energy and reducing collision-induced energy loss. This in turn significantly promotes diamond nucleation, secondary nucleation and grain refinement, thus facilitating the growth of nanocrystalline diamond. In contrast, an excessively high pressure yields the opposite effect, inhibiting nucleation and promoting grain coarsening. Full article