니켈 도금층의 경도와 잔류응력

Study on the Hardness and Internal Stress of Nickel Electrodeposit

Hardness and internal stress are very important in nickel electrofonning. Nickel sulfamate bath has been widely used in electrofonning because of its low intemal stress and moderate hardness. Nickel sulfamate bath without chloride was chosen to investigate the effect of plating variables such as temperature, PH, current density and sodium naphthalene trisulfonate on the hardness and intemaI stress. It was found that hardness increased with increasing temperature and decreasing current density and ranged from 150-310DPH. The hardness was highest at 55 'C and 10-40mA/㎤. The intemal stress increased with increasing current density and decreasing temperature. It was minimum at PH 3.0-3.8. Low intemal stress within ±1,500psi was obtained at both 50'C and 55 'C in 10-20m/㎤. The addition of sodium naphthalene trisulfonate was found to be effective in refine columnar grains thus resulted in decreasing intemal stress, increasing hardness and improving brightness.