Đang chuẩn bị liên kết để tải về tài liệu:
The Materials Science of Coatings and Substrates Part 2

Tham khảo tài liệu 'the materials science of coatings and substrates part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 26 Electrodeposition Since many practitioners believe that a delay between plating and baking could be important another experiment was run with just two variables baking time and delay before baking. Bright cadmium plated specimens were baked for 3 and 72 hours with delays before baking of 1 4 and 24 hours 20 . Data in Table 5 show diffusable hydrogen concentfation as a function of baking time and delay before baking. Results clearly reveal that there was no effect on the hydrogen concentration whether or not the baking was done as soon as possible after plating. In spite of these results it is possible that elapsed time between plating and baking can be sufficiently long enough that die migrating hydrogen reaches the critical concentfation for crack initiation. No amount of baking will ever repair these cracks the substrate will have a permanent reduction in yield strength 21 . Table 5 Two Variable Two-Level Experimental Design and Results for Bright Cadmium Plated 4340 Steel a Trial Baking Time h Time h Hydrogen Concentration pA cm2 Avg. 1 3 1 4 0.88 1.26 1.07 2 3 24 1.08 1.02 1.05 3 72 1 4 0.26 0.31 0.28 4 72 24 0.28 0.31 0.30 a. From reference 20. Background level was 0.22 pA cm2 Cd-Ti Plating Cd-Ti plating an approach to inhibit hydrogen embrittlement was introduced in the 196O s 22 . This technique utilizes a standard cadmium cyanide solution with a sparsely soluble titanium compound plus hydrogen peroxide. When properly operated the deposit contains from 0.1 to 0.5 Ti. This process has been used for coating high strength landing gear Hydrogen Embrittlement 27 actuation cylinders linkage shafts and threaded rods subjected to high stress 23 . A noncyanide elecưolyte prepared by adding a predissolved Ti compound to a neutral ammoniacal cadmium solution is also available 24 . With this elecưolyte fine-grained Cd-Ti deposits containing 0.1 to 0.7 Ti have been obtained. It is reported that with respect to throwing power corrosion protection and hydrogen .