(06-23-2017, 07:26 AM)sprayloud Wrote: I am asking because i got a drop in hardness of the coating by ~8HRC.
Could this happen if the temperature was >1000C ?
When the temperature of the heat treatment exceeds 1040°C, the layer is partially melted. This melt is an eutectic in the Ni-Cr-B-Si system and contains much boron and silicon which are responsible for the hardness of the layer. Thus, when this eutectic melt flows away from the part, more nickel and fewer boron and silicon remain in the layer as compared with the pre-heat treatment state. Loss of boron and silicon also means loss in the hardness of the layer.