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The Al/Ni Cu composite coatings were deposited on the surface of a pure Ti substrate by plasma spray technology and arc spray technology,and then the sprayed Al/Ni Cu/Ti specimen was then heated in the furnace at 700 ℃.A Ni-Al intermetallic compound protective coating with oxidation resistance formed through in-situ reaction between Al and Ni Cu composite coatings. The microstructure of the coatings before and after heat modification treatment and the formation mechanism of Ni-Al intermetallic compounds were studied. In addition,the oxidation tests of the Al/Ni Cu/Ti specimen( after heating and polishing treatment) and the uncoated Ti at 800 ℃ for 100 h were conducted. The results show that,by modifying Al/Ni Cu spray coatings on Ti substrate with furnace heating treatment at 700 ℃,Ni Al3,CuAl2,Ni2 Al3 and Ni Al intermetallic compounds with certain Cu elements form through in-situ reaction between Al/Ni Cu composite coatings. However,only the Ni Al intermetallic compound with high melting point can stay stable,and this intermetallic compound can protect Ti substrate under high temperature.