Sulphamate nickel

As already mentioned, electroless coatings are harder than conventional electroplated articles and as a result the wear resistance is increased. This property restricts the ductility of the deposit, with elongation values of 1-3% being found for electroless nickel. The residual stress is far higher than that of a sulphamate nickel electroplate and is generally tensile, which can be a serious hazard in certain industrial situations where crack propagation has to be avoided at all costs. 

One should note that nickel, in comparison to copper, is a less thermal conductive material. Here, it is possible to manufacture molds that consist of 1 to 2 mm sulphamate nickel which will then be reinforced with hard copper. This combination combines the advantage that nickel offers, with the good thermal conductivity of copper. 

Mold shells from sulphamate nickel with a wall thickness of about 3 to 4 mm, which are heated either with hot air or in a sand bed, where cooling is done through spraying with a water-air mixture or though cold air. 

Mold shells from sulphamate nickel with a wall thickness of about 4 to 5 mm, soldered onto the temperature control pipes made from steel, so that heating and cooling can be done using heat transfer oils (Figure 1.187). 

The bath model is prepared (as described above), made electrically conductive, and put into a sulphamate nickel bath for an electroplated deposition. Depending on the size, geometry and required wall thickness, the model stays between three to seven weeks inside the electroplated hath including disruptions (to renew auxiliary anodes and insert covers). When reaching the required wall thickness, the process is ended and the mold shell is ground to the outer contour. If necessary, the flange surfaces have to be milled, and fixed bore holes have to be drilled. After thermal or chemical demolding of the bath models, the inner contour is cleaned, the mold is measured, values are compared to the CAD data, and a defined surface treatment is applied. 

Deposits from Watts-type solutions Most coatings of nickel for engineering applications are electro deposited from a Watts-type bath Typical mechanical properties of deposits from Watts and sulphamate solutions are compared with those of wrought nickel in Table 13.15. 

Deposits from other solutions Nickel can be deposited from solutions based on salts other than the sulphate, chloride and sulphamate. Solutions based on nickel fluoborate, pyrophosphate, citrate, etc. have been extensively studied but none of them is used to any significant extent in Europe for engineering deposits. 

Wearmouth has described the production of nickel-cobalt, nickel-manganese, and nickel-chromium alloy coatings for non-decorative uses. The nickel-cobalt and nickel-manganese are electrodeposited direct from sulphamate-based solutions, the nickel-cobalt alloys offering higher hardness than the nickel-manganese alloys, which are restricted to a relatively... 

The thickness of the foil will depend on the current density and the rotation rate of the drum. A system designed to produce nickel foil, 0.5 mm thick and employing a strongly stirred, concentrated sulphamate electrolyte so that a current density of 0.5 A cm" may be used will produce about 1 m h of the foil. The width may be up to 1 m. 

Deposition of nickel at rates up to 1 mm/h in the concentrated solution is described by Kendrick . If pure nickel anodes are operated at a current density between 0-5 and 1-OA/dm in sulphamate solutions, a substance which behaves as a stress reducer is produced continuously in sufficient quantity that the stress in deposits can be varied at will from compressive to tensile by adjusting cathode current density and solution temperature. This finding is exploited with the concentrated sulphamate solution in the Ni-Speed process , and in a further development cobalt is added to give deposits of... 

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