CVD diamond (CVDD) films have many excellent characteristics and hold potential as a coating material for use in various fields. Applications in cutting tools are well known, but sufficient utility in practice has not been achieved. One of the largest technical problems is delamination caused by strong impact when cutting work-piece materials. In the case of cemented carbide tools, in particular, removal of Co contained as a binder from the surface of substrate is indispensable, because, in the first stage of CVD, C dissolves into Co and a brittle substrate/CVDD interface is formed. This paper describes a novel surface design technique that optimizes the surface of cemented carbides for improvement of the adhesion strength of CVDD films. With the specific surface treatment of cemented carbide in a plasma atmosphere, extremely favorable surface conditions for the synthesis of CVDD can be obtained in a short period. That is, this reformed surface promotes removal of Co from the uppermost surface and also has roughness formed by recrystallization of WC grains that results in an anchoring effect and increase of the contact area.
The synthesis of diamond or DLC film in the atmosphere was investigated using an improved combustion flame apparatus equipped with a substrate revolution system. The films have been synthesized at conditions involving of substrate revolution at 0 to 900rpm, a gas composition of C2H2 fixed at 3.0SLM, O2 was 2.4 at 2.7SLM, and deposition time of 90 minutes at atmospheric pressure. The substrates used were cemented carbide (WC-6%Co). Using SEM observation of the surface morphology, deposits were covered with Diamond (111) surfaces with a grain size of 10μm in diameter at C2H2:O2=3.0:2.7gas composition without revolution. The deposits at C2H2:O2=3.0:2.4 consisted of fine grains and the surface appeared glass like. The qualities of the deposits have been estimated using Raman spectroscopy. The deposited film was found to be a diamond, because a Raman band was observed at 1333cm-1 at C2H2:O2=3.0:2.7 gas composition. On the other hand, the deposit at C2H2:O2=3.0:2.4 gas composition have bands at 1350cm-1 and 1600cm-1, and were identified as a mixture of amorphous carbon and graphite. The deposits changed from DLC to diamond with an increase in the oxygen content, and the deposit at C2H2:O2=3.0:2.7 was identified as high quality diamond in particular. The effects of substrate rotation were such that diamond was deposited without revolution, and that deposits changed to DLC consisting of small grains at higher revolutions. The deposit at C2H2:O2=3.0:2.5 gas composition and 600rpm substrate revolution were identified as DLC because Raman bands were displayed at a center band of 1550 cm-1 and at a 1400cm-1 shoulder band. Regarding the effects of revolution, diamond was formed at C2H2:O2=3.0:2.7 without revolution, but the deposited surface because finer with an increase in revolutions. Results of Raman spectra confirmed that the deposits changed from diamond to DLC with revolutions. Control of deposits of either diamond or DLC will be possible via selection of conditions such as gas component or substrate revolution.
Widely used for can stocks electrolytically chromium-coated steel (ECCS) laminated with biaxially oriented polyester films is usually subjected to heat treatment in a wet condition such as retort treatment in the filling process. This heat treatment is a factor that decreases the adhesive property for polyester film and ECCS. The effects of heat treatment in a wet condition on the adhesion of a polyethylene terephthalate (PET) film to ECCS were investigated in connection with the structural changes in the PET compared to the changes after annealing in a dry condition. The adhesivity was evaluated with T-peel tests, and the properties of the PET film were appraised using density measurements, X-ray diffraction, an infrared spectroscopic method, and molecular weight measurements. The adhesivity in both wet and dry annealing conditions decreased with the progress of crystallization and degradation at 90°C and 130°C, though it did not change at 50°C. Additionally, the adhesivity in a wet condition was worse than that in a dry condition because the hydrolysis of the PET in a wet condition progressed faster than the thermal degradation in a dry condition.
A colloidal hydroxide solution consisted of nickel sulfate, copper sulfate, and tartaric acid was prepared as a substitute for a palladium catalyst in nickel-phosphorus electroless plating. The colloids were adsorbed on an ABS resin substrate and then reduced chemically to produce activated sites for electroless plating. After nickel-phosphorus electroless plating, the articles were used for the evaluation of the 90°peeling strength and of the initial covering velocity with the nickel-phosphorus film during the electroless plating. Results indicated the following. (1) An ABS resin substrate treated with the colloidal solution yielded an adhesion strength for the plating film as strong as one activated by a conventional coupling of tin (2+) ions as sensitizer and palladium (2+) ions as activator for the electroless plating. The ABS resin substrate, in particulars activated using a colloidal solution of pH 7.8 consisting of 0.08mol/dm3 nickel sulfate, 0.01mol/dm3 copper sulfate and 0.04mol/dm3 tartaric acid, caused cohesive-destruction with the plated nickel-phosphorus film during the 90°peeling strength test. (2) Both copper ions and copper hydroxide in the colloidal solutions served to reduce the time for the ABS resin substrate to be covered uniformly by the nickel-phosphorus film during electroless plating. However, they tended to enhance the surface roughness.