The effects of alumina on the hybrid microwave sintered ferum-chromium metal matrix composites

The main problem with conventional sintering is because of the lower heating rate leads to longer processing time, resulted in higher energy consumption. To overcome the problems, sintering with microwave energy has been introduced. However, this research is still new and limited to some pure metals, pure ceramics and a few types of composite materials only. This study involves fabrication of ferum-chromium (Fe-Cr) matrix reinforced by alumina (Al2O3) particles sintered under hybrid microwave energy at four (4) different sintering parameters such as compaction pressure, heating rate, sintering temperature and holding time. The study were focused on determination of the optimum mechanical properties such as bulk density), total porosity and micro hardness and mechanical wear characteristics in-term of volume lost (mm3), wear rate (mm3/s) and wear coefficient (K) by varying the Al2O3 particles content from 5 wt.% to 30 wt.% of fe. Hybrid microwave sintering was performed using microwave furnace Hamilab-V3 at 2.45 GHz at output power of 3kW. This study found the optimum condition for compression pressure, heating rate, sintering temperature and holding time occurred at 700 MPa, 20°C/min, 1400°C and 45 minutes. Total sintering time under hybrid microwave energy at this setting was 130 minutes compare to 340 minutes achieved by conventional sintering. This means hybrid microwave sintering was 62% faster than conventional sintering. Incorporating of 30 wt.% Al2O3 particles to Fe-Cr matrix deteriorated the bulk density from 6.652 g/cm3 to minimum at 4.08 g/cm3 and concurrently, increase in total porosity percentage from 11.24% to 22.60%, microhardness achieved at highest value at 170HV. This study revealed that mild wear occurred for sample with low Al2O3 particles at 5 wt.%, 10 wt.%, 15 wt.% and 20 wt.%. Severe wear mostly by abrasive wear significantly occurred for samples with 25 wt.% and 30 wt.% of Al2O3 content. The wear resistant coefficient (K) was found at highest value 1.2 x 10-1 for the Fe-Cr composite reinforced with 30 wt.% of Al2O3 particles. The high wear rate that contributed aggravated wear resistant occurs at 25 wt.% and 30 wt.%, while the low wear rate that provide highest wear resistant was achieved when between 5 wt.% to 20 wt.% of Al2O3 particles is added to Fe-Cr matrix.