Akademik Veri Yönetim Sistemi
JOURNAL OF POLYTECHNIC-POLITEKNIK DERGISI, cilt.24, sa.2, ss.703-710, 2021 (ESCI)
Lubricants used in the Powder Metallurgy (PM) method significantly affect the compressibility, flowability and apparent density of metal powder and also strength of sinter parts. In this study, sintered powder metal (P/M) materials were produced by hot pressing of pre-mixed Alumix 123 powder with w.t. 1.5% zinc stearate (ZnSt) lubricant. The pre-mixed Alumix 123 powder with lubricant were mixed for 40 minutes in the three-dimensional mixing device and pre-compression was carried out at pressures of 100, 300 and 500 MPa. Then, the die temperature was increased by 50 degrees C and kept for 15 minutes in between 300-450 degrees C. By this way, a total of 1 hour lubricant removal process was performed. Subsequently, hot pressing active sintering was applied for 30 minutes under a pressure of 50 MPa at 540 degrees C. The same processes were applied to the pre-mixed Alumix123 powders without lubricant, except the mixing process. Diffusion annealing (DA) with eutectic temperature change (548 degrees C +/- 10 degrees C) was applied to the produced P/M materials. Density measurements according to Archimedes principle and hardness measurements of P/M materials were made. Metallographic examinations of these produced parts were carried out. At the same time optical microscopy, Scanning Electron Microscopy (SEM/XRF) and also X-Ray Diffraction (XRD) analyzes were performed. Increasing the pre-compression pressure in lubricant-free P/M materials decreased the pore density and increased the relative density. The lubricant removal effect with increasing pre-compression pressure and the relative density of P/M materials reduced. It has been determined that the density, hardness and alloying rate of the samples produced without lubricant are higher than those with lubricant.