Microstructural and morphological evaluation of MCrAlY/YSZ composite produced by mechanical alloying method

This paper investigates CoNiCrAlY/YSZ composite materials produced by mechanical alloying process. Various amounts of YSZ particles (0%, 5%, 10% and 15 wt.%) were mixed with CoNiCrAlY powder and milled for 12, 24 and 36 h. The structural and mechanical evolutions of the mechanically milled powders were executed using X-ray diffractometry, scanning electron microscopy, optical microscopy and micro-hardness test. It was observed that by increasing milling time, the internal lattice strain of γ-phase matrix increased while grain size of this phase decreased. Also, addition of YSZ to CoNiCrAlY decreased the rate of grain size reduction. In comparison with milled CoNiCrAlY powders, CoNiCrAlY/YSZ milled powders exhibited more spherical morphology and narrower particle size range. Moreover, the increase in milling time caused the homogenous distribution of ceramic particles in CoNiCrAlY matrix, while the increase in YSZ percent decreased the homogenous distribution of ceramic particles in CoNiCrAlY matrix. Besides, micro-hardness tests illustrated that the effect of milling on hardness is more significant than that of ceramic particles addition.

► The grain size of CoNiCrAlY decreased as milling time increased. Adding YSZ, delayed decrease of grain size of matrix alloy.
► Increase of milling time and YSZ percent resulted in spherical morphology and homogenous distribution of powders. Adding YSZ also delayed cold welding phenomenon.
► At initial stage of milling, CoNiCrAlY powder showed the greatest hardness but with increases milling time powders contained 15% YSZ showed the maximum hardness.