Study on Properties of Electroforming Hard Gold

In order to have a clearer idea about the properties of electroforming hard gold，the authors select three samples of electroforming hard gold from three companies and test them by using ICP－MS，ICP－AES，micro－hardness tester，metallurgical microscope and scanning electron microscope.The results indicate that the content of Au is greater than 99.9%in each sample，their main trace elements are Ag and Cu.Vickers hardness of the three samples are 68.74，71.16and 74.97respectively and all of them are lower than 145.In terms of structure，crystalline grains of the samples are so fine that they can not be distinguished even by SEM and the tiny grains are the structural basis for high Vickers hardness.Meanwhile，the surfaces of smaples are uneven with many holes，and their structures are rather loose.There are some inclusions in each sample，the size of the inclusions is between 0.2μm and 3.5μm.The inclusions in sample 1are mainly composed of CaO and Na₂O.The inclusions in sample 2and sample 3are mainly composed of SiO₂and Na₂O.These results probably are due to the liquid solution where the samples are produced.The Vickers hardness of sample 1 is 68.74and it is reduced to 25.94after heat treatment，which is caused by the“growing”of the crystalline grains after being heated.