Fundamental aspects of a plasma sprayed cast iron coating on an aluminum alloy substrate are investigated in the present study: focusing on the effects of preheat substrate temperature (TS) and chamber pressure (PC) on the splat morphology, the adhesive strength of splats, the formation of a reaction layer and graphite. Splash-type splats appear at low TS but disk and star-shaped splats arise at high TS. Deformed substrate ridges, mainly due to the slight surface melting, are formed adjacent to the splat periphery at high TS. At low TS, pores are observed at the splat/substrate interface, which cause a decrease in the adhesion of splats. In contrast, a reaction layer composed of iron, aluminum and oxygen is ready to form at high TS. The amount of graphitized carbon increases in cast iron splats with TS. At a low PC of 26.3 kPa, disk-type splats are in the majority at a constant TS of 473 K. As PC increases, star-shaped splats appear along with disk splats. The flattening ratio of disk splats decreases with the increase of PC, because of a decrease in the kinetic energy and temperature of molten droplets. An interfacial oxide layer composed of iron, aluminum and oxygen is ready to form at high PC. The number of pores intensively increases with PC, which leads to a decrease in the adhesive strength of splats. The amount of formed graphite in cast iron splats slightly increases with PC, however, that of a rapidly solidified phase of Fe-Si-C decreases because of lowering of the solidification rate.