In the paper the aluminide layer was deposited by CVD method on the CMSX 4 single crystal nickel base alloy. The aluminizing process was carried out at the 1050 °C during 8 h. The chemical vapor deposition process was performed by means of AlCl3 aluminum chloride. The effects of aluminizing were verified in microscopic examination (microstructure and depth layer) and chemical composition on the surface and cross-section of aluminide layer. The oxidation resistance in the air atmosphere at the 1100 °C during 1000 h was a criterion of efficiency of CVD process. The hardness distribution on the cross-section aluminide layer before and after oxidation test was investigated. The parabolic mass change was observed during oxidation. Under oxidation test during 120 h on the grain size of NiAl phase was observed the phase transformation β NiAl →Ni3Al. The increase of oxidation time causes decreasing of substrate hardness and stabilization of Topologically Closed Packed phases.