Microwave sintering and mechanical properties of PM copper steel

Microwave processing has gained worldwide acceptance as a novel method for heating and sintering a variety of materials from food to rubber to specialty ceramics, as it offers specific advantages in terms of speed, energy efficiency, process simplicity, novel and improved properties, finer microstructures, and lower environmental hazards. In the present paper, microwave sintering of modulus of rupture (MOR) bar samples of PM copper steel (MPIF FC-0208 composition) and the comparative evaluation of the mechanical properties using both microwave and conventional sintering techniques has been reported. The starting powder characteristics and the processing details of copper steel bar samples sintered in a conventional furnace and in an in house modified commercial microwave oven has been covered at length. In this study, the sintering temperature used typically ranged between 1100 and 1300degreesC, soaking time ranged from 5 to 20 min, and the atmosphere was controlled using flowing forming gas (mixture of 95% N-2 + 5% H-2). Microwave sintering resulted in higher sintered density, higher Rockwell hardness (HRB), and higher flexural strength as compared with conventional sintering. The improved mechanical properties of microwave sintered samples can be mainly attributed to the evolution of distinct porosity distribution, primarily consisting of small, rounded, and uniformly distributed pores as against large, angular and non-uniformly distributed pores observed in the case of conventional sintering.