To examine the adequacy of densified Ni-Al intermetallic coatings as a surface modification process, the intermetallic compound by SHS reaction was coated on a spheroidal graphite cast iron substrate. The results obtained are that the void ratio in reaction layer after SHS reaction decreases with increasing pressure at cold pressing in the preparation of powder compact and pressure at hot pressing. Secondly the bondings between reaction layer and substrate are sufficiently achieved at all the conditions without compressing at hot pressing, but the conversion of SHS reaction layer to full densification is incomplete.