|Budget Amount *help
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 2006: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2005: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2004: ¥900,000 (Direct Cost: ¥900,000)
We evaluated the characteristics of the composite coating formed by thermal spraying of Cn-Ni system alloy powder blended with CaF_2 powder. When the composite coating was subjected to insert treatment with cast iron, a problem of gas detect specific to composite coatings occurred. The results of implementation of various solutions for this problem are given below.
(1) CaF_2 forming a layer structure dispersed uniformly in the composite coating. As the CaF2 blended ratio became higher, the CaF_2 area fraction increased. The hardness was lowest when the CaF2 area fraction was approx. 6%.
(2) As the result of Falex test for the composite coating, it was revealed that the wear loss decreased as the quantity of CaF_2 serving as a solid lubricant in the coating increased and that the coefficient of friction became lower when the temperature near the friction surface was higher than 200℃.
(3) A large quantity of oxide exists in the composite coating. When the coating was inserted directly with
cast iron, the carbon in the cast iron reacted with the oxide to generate CO gas, resulting in gas defect.
(4) Then, we revealed that the composite coating could be bonded when the coating was inserted with cast iron after a bond coat of pure copper was sprayed over the coating and the coating was embedded in charcoal to subject it to deoxidation treatment (1023K, 12hrs).
(5) When the spraying was performed while cooling air was flowing in a copper pipe (20-mm-diam), the layer structure of the composite coating became blurred.
(6) When a thin copper pipe (6-mm-diam) was put in the center of the copper pipe to which coating had adhered during insert treatment, the space between the outer pipe and the thin pipe was filled up with foundry sand (#6) and the inside of the thin pipe was cooled with air, the composite coating melted because the cooling capacity of air is low, and cavities occurred in the interface between the coating and the cast iron. When the pipe was cooled with water in place of air, the bond coat melted, and the final solidification part of the cast iron caused contraction.
(7) When the copper pipe (20-mm-diam) to which the composite coating had adhered was cooled with water directly from the inside, the cast iron was rapidly cooled, and the thin part of the casting showed chilling. Less