The effect of plasma sprayed under layer coating (Ni-A195-5) thickness variation on both adhesion strength and tribological behavior of top layer ceramic coating (A1203 TiO3) was studied. Series of microscopic investigation were carried out on both under layer and top layer coatings of test specimens, which were manufactured from base metal alloy steel 15Cr Ni 6, to measure the porosity, unbounded particles, interfacing and oxide particles content percentages which were found within the permissible limits of ASTM specification. Also, a series of coating tensile adhesion strength tests and wear experiments carried out using the specified specimens. The microhardness of layers structure are reported. A relation ships between the adhesion strength, microhardness of the two layers and wear losses against the underlayer thickness variation were predicted. From these curves and measurement, the optimum plasma sprayed under layer coating thickness for the top layer plasma sprayed ceramic coating was determined.