Abstract
One of the features of chromium plate is its extremely high hardness. In the present study, the hardness of chromium plated surface was measured by Vickers hardness tester and scratch hardness tester. It was found that both methods gave the same trend in the hardness of chromium deposit.
The hardness of the chromium deposit is greatly influenced by the plating condition and heat treatment. Investigated here are bath temperature, current density, composition of bath, and temperature of heat treatment.
The conclusions summerized are as follows.
The conditions suitable for the preparation of bright deposit were found to be favorable to obtain hard deposits.
The hardest deposit was produced when the ratio of CrO3/H2SO4 by weight was 70-80 in the solution containing 250g/l CrO3.
Upon heating to about 150-400°C, hardness of the bright chromium deposits decreased slowly. Rapid decrease in hardness was observed at about 400-600°C, and, after that, the decrease became more slowly. On the other hand, in regard to soft milky chromium deposits, rapid decrease in hardness occured at about 550-700°C or 700-850°C.
