This study eva‎luated the effect of thickness on corrosion and wear behavior in both conditions before and after heat treatment. Copper was used as substrate material. To create an alkaline nickel boron bath were used nickel chloride as the source of nickel ion, sodium borohydride as the source of boron ion, ethylenediamine as the complexing agent, thallium acetate as the stabilizing agent, and sodium hydroxide as the buffering agent. The pH and temperature of the electroless nickel boron plating bath were kept in the range of 12-13 and 80-85° C during coating, respectively. The deposition was done in three different thicknesses. The heat treatment was done at 450° C for one hour. The study items included morphology, XRD diagram, roughness, hardness, corrosion, wear, and friction coefficient of coatings, which tests were used of scanning electron microscopy, X-ray diffraction, laser profilometry, Vickers hardness tester, Potentiostat, and pin on disk test. The morphology of the nickel-boron coating showed that the structure of the coating was cauliflower shaped and the thickness of the coating increased with a growth in the size of the cauliflower. Heat treatment of the coatings also increased the size of the cauliflower. According to the obtained results, increasing the thickness of the coating, increased the amount of roughness and consequently, due to the increase in the contact surface, increases the coefficient of friction. The heat treatment of the samples reduced roughness and was observed a lower coefficient of friction so that the sample of heat treatment with the least thickness had the lowest amount of roughness and coefficient of friction. Examination of the corrosion behavior of the coatings showed that increasing the thickness of the coating, has improved the corrosion resistance. The reason for the improvement in corrosion resistance could be that with increasing thickness, increased size of the cauliflower shapes in the coating structure, which fills the pores in the subsequent layers of sediment. However, heat treatment reduces the corrosion properties because it changes the structure from amorphous to crystalline, and the formation of grain boundary and grains, which are prone to corrosion cells. The results of scanning electron microscopy showed the wear path of both abrasive and adhesive wear mechanisms for the coatings, but in as-plated coatings with increasing thickness, the adhesive wear mechanism became more dominant, while in heat-treated coatings with increasing thickness, the abrasive wear mechanism became more dominant.

عبدالمجيد اسلامي، محمدعلي گلعذار

كيوان رئيسي، احمد منشي