Fabrication and assessment of mechanical properties of open cell porous regular interconnected metallic structure through rapid manufacturing route

Abstract

Purpose

The requirements of open cell porous regular interconnected metallic structure (OCPRIMS) in applications such as heat exchangers, sound absorption, fluid flow control, spark arresters and biocompatible inserts have been increased. As per available technology in the present scenario, only the metallic-based rapid prototyping (RP) machines can guarantee fabrication of OCPRIMS. Metal-based RP machines are capital-intensive. So, this study aims to develop a technique for fabrication of OCPRIMS economically using three-dimensional printing (3 DP) and pressureless sintering.

Design/methodology/approach

Three computer-aided design (CAD) models of varying designed interconnected porosity 73, 70 and 60 per cent were modeled to target metallic porosity 27, 30 and 40 per cent. The same were fabricated with ceramic-based powder using 3 DP. Thereafter, spherical bronze powder with average size of 200 µm was filled and sintered in pressureless manner under inert atmosphere of argon. After sintering, the specimens were cleaned with the help of pricking needles and high-pressure water. It flushed the burnt ceramic powder and allowed metallic portion to remain intact. The obtained specimens were inverse of CAD/3 DP models. The dimensional measurement at different stages of fabrication was carried out to find shrinkage. Sintered density and interconnected porosity were measured using Archimedes’ principle. The characterization of the fabricated specimens was done with the help of microstructure analysis, scanning electron microscopy and energy dispersive x-ray analysis. Mechanical properties were assessed using compressive, tensile and Charpy tests.

Findings

The feasibility has been explored successfully to fabricate OCPRIMS of phosphor bronze using 3 DP and pressureless sintering process. Interconnected porosity of 51.45, 56.45, 64.09 per cent of final metallic specimens has been observed against the targeted 27, 30 and 40 per cent. The increase in pore dimensions up to 19.13 per cent and shrinkage up to 5.44 per cent of outer dimensions were found to be the main causes of increase in interconnected porosity level. The characterization results exhibit the behavior of pressureless sintering process and stability of the fabricated specimens. Mechanical properties of fabricated structures are found to be dependent on porosity and strut diameter. Compressive and tensile strength decrease with the increase in porosity for strut diameter less than 1 mm, whereas they increase with the increase in strut diameter of 1 mm or more. A similar trend has been observed for impact strength also.

Originality/value

This paper explores the feasibility to fabricate OCPRIMS economically using 3 DP and pressureless sintering process.

Citation

Singh, J.P. and Pandey, P.M. (2018), "Fabrication and assessment of mechanical properties of open cell porous regular interconnected metallic structure through rapid manufacturing route", Rapid Prototyping Journal, Vol. 24 No. 1, pp. 138-149. https://doi.org/10.1108/RPJ-04-2015-0043