Cobalt containing carbide powders such as WC-Co and WC-Co-Cr for thermal spraying exist in numerous modifications varying in chemistry, carbide size, and production method. They are widely used for wear, erosion and corrosion protection in many industrial fields. However, for decades it has been well-known from the hard metal industry that WC and Co containing hard metals in breathable dust form can provoke severe lung diseases if inhaled. Recent examinations have proven that this toxicity can be significantly reduced if the Co is pre-alloyed by Fe. In thermal spraying employees are also dealing with Co containing carbides, for example in powder and coating production. Therefore, in order to reduce the hazards for health and the environment, a new class of agglomerated and sintered carbide powders using Fe based binder materials have been developed and investigated. In the present study the powders were HVOF sprayed in order to examine the influence of their different composition and morphology on the microstructure and the properties of the coatings in comparison to standard materials. The experiments comprise microstructural examinations, wear and corrosion tests.

In a joint development project, TACR GmbH1 and H.C. Starck GmbH 2 took an approach to adjust the properties of an agglomerated and sintered YSZ powder to a process setup optimized for a HOSP type powder. Within the OEM approved process parameters, which could be changed within narrow limits only, the particle size distribution of the agglomerated and sintered powder was adjusted to meet process parameters and spray setup. Key parameters for the comparison of coating properties and spray behavior were coating porosity and deposition efficiency (DE).