Abstract
Using PM technologies, new antifriction materials based on iron powder with different addition elements were developed in order to obtain self-lubricated bearings with improved tribological features. The elemental powder mixtures were blended for 2 hours in a 3D homogenization device, were compacted at a pressure of 500 MPa, and then sintered in dry hydrogen atmosphere at different temperatures for different maintaining times. The effect of technological parameters on physical properties (density and dimensional changes) was presented in this study. The mechanical and tribological properties (tensile strength, hardness, impact energy, friction coefficient, and wear rate) related to addition elements were evaluated. The tribological behaviour of the selected iron-based alloys was analysed by pin on disc tests without lubrication. Also, the wear surface scars and the microstructure of the wear surfaces were investigated.
Highlights
Self-lubricating bearings represent the oldest industrial application of the porous materials obtained by PM technique as metallic filters and sparking plugs cannot be produced by other technology
(ii) Generally, as the sintering temperature increases the smaller values of the density are obtained due to volumetric dimensional growth during liquid-phase sintering at higher temperatures
(v) Tensile strength of 205 MPa, hardness of 139 VH5, and toughness of 12.5 J/cm2 were obtained for alloys sintered at 900◦C for 50 minutes and containing 2.5% Sn due to the presence of strengthening phases which form at higher temperatures and longer sintering times
Summary
Self-lubricating bearings represent the oldest industrial application of the porous materials obtained by PM technique as metallic filters and sparking plugs cannot be produced by other technology. As the quality of the material powders and the manufacturing processes were improved, powder metallurgy parts had in many cases taken the place of cast and forged products It is very important, in order to avoid subsequent operations such as sizing and machining, to improve the final dimensional tolerances obtained after sintering. The density of the sintered parts was investigated and, the effect of the sintering temperature and time on the density of the iron-based materials for self-lubricating bearings was studied. These influences of the sintering parameters on the density and dimensional changes are presented as 3D surface plots using Statistica software
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