On the certification and Specification of WC-Co Type Powders

Experience in developing and manufacturing powders and their use as coatings with various spray processes with reference to coating properties has resulted in many manufacturers’ designations but few standards. As coatings become part of the bill-of-material for many high-risk components and as the spray process becomes more industrialized a need is seen to ensure that powders are certified specific for the spray method employed together with the coating application and the specific coating properties.

In the case of HVOF spraying, the issues with WC-Co type material cover their metallurgy, manufacturing characteristics, size of primary carbide, apparent density, phase transformation during spraying and the need to ensure a specific particle size distribution depending on the spray gun and fuel combinations being employed. On the commercial side, questions need to be raised regarding powder deposition efficiency and reclamation of the original powder value through the overspray.

This paper reviews the present situation regarding the WC-Co type materials with HVOF with regard to specifying the materials and the resulting certification.