Additive Manufacturing of Silicon Nitride Ceramic Floatation Spheres with Excellent Mechanical Properties

Hai Qi,Fangquan Guo,Weiyue Han,Miaofeng Du,Fen Wu,Chenggui He,Peizhi Zhang

doi:10.3390/ma12172717

Hai Qi, Fangquan Guo + Show 5 more

Open Access

https://doi.org/10.3390/ma12172717

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Journal: Materials	Publication Date: Aug 24, 2019
Citations: 4	License type: CC BY 4.0

Affiliation: Shanghai Research Institute of Materials

Abstract

Silicon nitride (Si3N4) ceramic materials are increasingly being used in deep-sea pressure-resistant applications because of their high compressive strength-to-weight ratio. In the present study, Si3N4 ceramic floatation spheres with an outer diameter of approximately 101 mm are successfully batch produced and evaluated. The implementation method was to prepare Si3N4 ceramic hemispherical housings and pair them together. In order to improve the safety of the joint, the hemispherical Si3N4 housings were gradually thickened from 1.80 to 2.50 mm at the equator near the joining surface, based on a 3D model with additive manufacturing technology. The weight-to-displacement ratio of the prepared floatation sphere is approximately 0.34 g/cm3. The flexural strength, compressive strength of the material and the collapse strength of a number of Si3N4 floatation spheres were tested to be 1150, 3847, and 205 MPa, respectively, to confirm the reliability of the process. Additional sustained and cyclic hydrostatic pressure tests simulating the full ocean depth working conditions are carried out on several Si3N4 floatation spheres, which perform very well and do not fail.

Highlights

Buoyancy modules and housings utilized in underwater vehicles demand deep-sea pressure-resistant materials with high compressive strengths and low densities to meet the requirements of water pressure resistance and reduce equipment weight
The epoxy resin powder was selectively melted by a laser bond theas ceramic particles together to form parts
This work demonstrates a new and feasible approach to realize batch production of deep-sea pressure-resistant floatation spheres with Si3 N4 ceramic material

Summary

Introduction

Buoyancy modules and housings utilized in underwater vehicles demand deep-sea pressure-resistant materials with high compressive strengths and low densities to meet the requirements of water pressure resistance and reduce equipment weight. Ceramic materials have a great advantage as deep-sea pressure-resistant materials because of their high compressive strength-to-weight ratio relative to high-strength steels and titanium alloys. Alumina (Al2 O3 ) ceramics were first used to produce hollow spheres as buoyancy modules [1,2,3] and external pressure housings for deep-sea vehicles [4]. Compared to silicon nitride (Si3 N4 ) ceramics (see in Table 1), Al2 O3 ceramics are not the best choice in terms of high compressive strength and low density. Si3 N4 ceramics have a high compressive strength-to-weight ratio and are, favored by many researchers.

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