Improvement of Mechanical Properties of WC-Cermet Coatings Prepared by High Velocity Air Fuel Spraying (Influence of Spray Gun Nozzle Geometry and Combustion Chamber on the Mechanical Properties of Coatings)

摘要

In high velocity air fuel (HVAF) spraying process, spraying particle temperature and velocity are one of the most important parameters. The spraying gun nozzle and the combustion chamber shape may influence on combustion gas and spraying particle behavior. Longer nozzle may accelerate particles effectively, and convergent-divergent nozzle makes supersonic flow. On the other hand, longer combustion chamber may provide higher particle temperature. In this paper, three convergent-barrel-divergent nozzles (CD-nozzle) and a convergent-barrel nozzle (C-nozzle) with two combustion chambers have been investigated. WC-10mass%Co-4mass%Cr cermet coatings are produced by each combination of the nozzle and the combustion chamber. These coatings were studied by micro hardness, abrasive wear resistance, and porosity. As a result, the spraying gun nozzle and the combustion chamber shape were critically influence on the HVAF cermet coating properties, and a CD-nozzle or a long combustion chamber can produce more wear resistance and dense cermet coating. It is required for further improvement and control coating properties to analyze combustion gas or particle behavior.