Dear Jumaa

The  coating process, i.e., organic or ceramic coatings, are normally used as a method to enhancement the shielding, protection, of  metallic materials, substrates, from the surrounding environment.

In stainless steels, when nitriding its surface with Nitrogen which diffuses interstitially several authors have found loss of resistance to the impact, which is due to that this type of coatings are used to improve the resistance to the corrosion, hardness ductility and Elastic limit, however with increasing hardness, also increases brittleness of steel.

Z.H.Jiang; Z. R. Zhang int j. Minem metal mater 17 (2010) 729-739.

 Dear Jumaa

The  coating process,  are normally used used as a method to enhancement the impact properties for metal material. Because if the coating material is nanosize and if it is coatted properly in the grain bounderies it may increases the cohesive energy, which leads to increase the toughness value. Due to coating there is increase in dimension of the specimen, If the dimensions of the specimen are increased, the impact strength also increases.The velocity of impact also affects impact strength to some extent, so it is also increases. Further it is generally expected that coating of nano material increases the overall thermaly propertis of the specimen, so the impact properties enhanced. Because The temperature of the specimen under test gives an indication about the type of fractures like ductile, brittle or ductile to brittle transition.

Yes, if the coatings have an excellent and higher impact property than the metallic substrate then these coatings considered as protective coatings leading to produce impact resistance metallic structure. In this case coating process can be used as a method to enhancement the impact properties of metal material.

Thanks Dr. mohanned for your answer

 Thanks for all answers