Reason for use:
Hardness is of interest to engineers because it relates to the tensile strength of wrought or cast metals, or because it gives an indication of resistance to abrasive wear.
With homogenous wrought or cast materials, hardness can be converted from one scale to another with reasonable accuracy by using appropriate conversion charts. Hardness of sprayed deposits cannot be converted into other scale or into tensile strength values.
Sprayed coatings differ in that they consist of many individual particles, are un-homogenous and may contain appreciable levels of porosity and oxides. Hardnesses of sprayed deposits must be treated with considerable caution. Values measured on a single specimen may vary depending on whether the area under the indenter contains porosity, oxide or uncontaminated coating. In general for unfused coating, Brinell hardnesses made with a large diameter ball will give the most consistent results. However, such impressions may penetrate deeply into the coating and particularly with thin deposits, may be influenced by the hardness of the basis material. Coating macrohardness tests are not recommended on deposits less than 3mm (0.125 in) thick.
The hardnesses given below are based on laboratory tests made at Metallisation Limited, certain Customers and Universities. They are for guidance purposes only, except under abrasive wear conditions, they should not be used for design purposes and even where abrasive wear is experienced, they should be treated with caution.
