Magnesium alloys have been anticipated as an ecologically sound application in industrial fields because of their light weight, recyclability, and high specific strength. Inferior wear resistance of magnesium alloys, however, hinders expansion of their application. The authors have improved tribological characteristics of magnesium alloys through application of diamond like carbon (DLC) coating on their surfaces. Results show that a DLC coating decreases the fatigue strength of rolled magnesium alloys. This paper describes experimental test results of friction and fatigue for DLC coated magnesium alloy (AZ31B) in combination with fine particle bombardment (FPB) surface treatment. The DLC/FPB combined surface treatment enables selection of an optimum friction coefficient and improves the fatigue strength of the rolled magnesium alloy. Microscopic fractography studies of fracture surfaces of tested materials show that microcracks on coating surfaces affect their fatigue strength. Microdimples formed by DLC/FPB surface treatment inhibit crack growth and improve the fatigue strength of DLC-coated magnesium alloys.
Plating on plastics is useful for manufacturing many plated metal products. When using ABS resin, which is often used for plating, etching pretreatment with chromic acid is conducted. This etchant can dissolve butadiene in ABS, forming rough areas on the surface, which are later filled with metals during plating. The consequent anchor effect produces strong adhesion of the metal to the resin. Nevertheless, few reports in the literature describe plating on polystyrene resin, which is widely used for home electrical appliances, amusement products, etc. This report describes an investigation of pretreatment using ozone water for plating on polystyrene resin. Results show high adhesiveness achieved from optimized pretreatment conditions. Furthermore, no anchor effect was necessary, as inferred from SEM observation and FT-IR analysis. Treatment using ozone water is applicable as a beneficial pretreatment for plating on polystyrene resin.
Watt’s nickel bath and nickel sulfamate bath are commonly applied for plating of micro-fabrication parts. In particular, the nickel sulfamate bath produces nickel plating with low residual stress and high tensile strength. Nickel sulfamate baths are therefore used extensively for electroforming and Micro Electro Mechanical Systems (MEMS). Boric acid is usually used as a pH buffering agent in the plating bath. However, boron-containing effluents are increasingly regulated because of environmental concerns. To solve these problems, organic acids such as acetic acid and citric acid were investigated as alternatives to boric acid. The pH buffering action of the organic acid baths was higher than that of the boric acid bath. Furthermore, the mechanical properties of nickel films obtained from a low-concentration nickel plating bath using an organic acid buffer were superior to those obtained from a bath buffered with boric acid. Nickel films with good mechanical properties were obtained from high-concentration nickel baths, which showed good pH stability even without a buffering agent in the formulation. Subsequent SEM and XRD analyses of these plating films revealed a defect free cantilever structure prepared with MEMS.