Improving Pressure–Velocity Limit of Mechanical Seal with Polycrystalline Diamond Coating

Daidong Guo,Shouhong Tan,Nan Jiang,Guoping Wu,Fangmin Xie,He Li,Ningning Cai

doi:10.3390/app10176090

Daidong Guo, Shouhong Tan + Show 5 more

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https://doi.org/10.3390/app10176090

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Abstract

Polycrystalline diamond (PCD)-coated mechanical seal rings were prepared by hot filament chemical vapor deposition (HFCVD) on graphite-loaded silicon carbide (GSiC) substrates. From the initial deposition process, the diamond first nucleated and then grew into a dense coating with grain size of 4 μm and thickness of 12.3 μm. The well-grown PCD coating, as confirmed by Raman spectroscopy and X-ray diffractometry, significantly improves the pressure–velocity limit of the mechanical seal applied in harsh operating conditions, no matter whether for a hard-to-soft mating combination or a hard-to-hard mating combination. Comparing GSiC against sintered silicon carbide (SSiC) combination (GSiC/SSiC), GSiC against graphite combination (GSiC/graphite) and PCD against graphite combination (PCD/graphite), PCD against SSiC combination (PCD/SSiC) shows the highest pressure velocity (PV) limit of 42.31 MPa·m/s with 4 kN loading at 4500 rpm rotation speed. An extremely low and stable friction coefficient and super mechanical properties under harsh conditions can be approved as the source of the high PV limit of PCD coating. A mechanical seal with PCD coating can be used for more demanding applications.

Highlights

Mechanical seals, which are readily available for sealing liquid and gaseous media, minimize liquid or gas leakage between the rotating shaft and stationary housing by maintaining a very small axial gap [1,2]
Seal ringuniformly was ground uniformly diamond size is about ring was ground with diamondwith grinding pastegrinding (particlepaste size is(particle about 0.1 μm) for 10 0.1 minμm) to for min to improve the nucleation density
Themorphologies morphologiesof of the the graphite-loaded silicon carbide (GSiC) substrate surface before and (SEM)

Summary

Introduction

Mechanical seals, which are readily available for sealing liquid and gaseous media, minimize liquid or gas leakage between the rotating shaft and stationary housing by maintaining a very small axial gap [1,2]. In these devices, the opposing faces of two annular rings, which form a rotating-stationary combination, contact together to obtain a sealing action. In heavy duty industrial applications, for example boiler feedwater, reactor cooling, oil and gas well drilling, mechanical seals require service at high speeds under elevated pressures [1].

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