Usual techniques such as PVD and CVD are not used for coating heavy industrial dies due to their size, and in order to increase their wear resistance and lifetime, conventional Hard chromium plating is used. The substitution of this technique with safer and more efficient ways has been recently studied and performed considering environmental pollution and restrictions for using Cr(VI) compounds, which are known to be carcinogenic. In this thesis, the lifetime of dies increases up to 200 percent by replacing hard chromium with thermal spraying process. Furthermore, the latter process does not contain biohazards of hard chromium technique. In order to replacement, hardness and adhesive strength were considered as coating specifications. Then HVOF Thermal spraying and 75Cr 3 C 2 -25NiCr cermet were selected as coating process and material respectively. Subsequently, to optimize the process, ine samples were coated by nine different parameters designed by Taguchi experimental program based on three levels of four parameters selected as following: Kerosene Flow Rate (KFR), Feed Rate (FR), Spray Distance (SD) and Substrate Surface Roughness (SSR). Nine microhardness and adhesive strength tests were used on samples. To evaluate adhesive strength, interface indentation test was used. Test results showed that SSR parameter has a significant effect on adhesive strength. By using machining instead of sand blast on the substrate surface, adhesive strength will decrease. Comparing adhesive strength when using machining with adhesive strength of literature, showed that despite the fact that adhesive strength will decrease by using machining of the substrate surface, it is still desirable. Accordingly, the sand blast process can be eliminiated to save time and cost of the thermal sprau process. The S/N ratio analysis approach was used in order to process optimization. Eventually, after optimization, a sample was sprayed under the optimized condition. To calculate the wear rate of the samples, three war tests were performed by using Pin Disc wear tester. Wear rate of the sample which was spraued under the optimized condition, was compared with a hard chromium coated sample and a sample having the least hardness. The results showed that optimized condition will improve wear rate by 26 percent. The results also showed 63 percent decrease of wear rate on the sample sprayed under the optimized condition compared to hard chromium coated sample, which means 200 percent increase in life time of Heavy IndustrialDies. The life time of the Heavy Industrial Dies in Iran isabout 2 milloin parts which can be increased significantly up to more than 6 million parts according to this thesis. Key words: die, hard chromium, HVOF thermal spraying, optimization, microhardness, adhesive strength, wear