HVOF spraying of fine feedstock powder allows the deposition of cermet coatings with outstanding properties, but selecting and optimizing process parameters can be difficult. In this study, investigators employ a design of experiments (DOE) approach to identify the most relevant process parameters in the spraying of 2-8 μm Cr 3 C 2 -NiCr powders. In a screening step, all parameters were assessed in a 12-run Plackett-Burman experimental design and linear models were used to estimate their effect on coating properties and deposition efficiency. The five most influential parameters were then analyzed in a 16-run fractional factorial set of experiments in order to determine their effect, along with all possible two-way interactions, on coating quality.

This paper presents a new strategy for improving the quality of HVOF sprayed coatings as well as the deposition efficiency of the process. The highly turbulent expanding gas jet is stabilized and focused with the aid of a helical gas shroud. The effect of the design modification is demonstrated by numerical calculations and through the use of a prototype torch.

The aim of this study is to analyze the shape of splats deposited by detonation spraying and correlate splat morphology with the velocity and temperature of particles as they hit the substrate. The obtained results are in good agreement with numerical calculations for nickel splats and show that the thermo-physical properties of composite particles can be estimated from their splat characteristics as well. An understanding of these relationships for various materials is necessary to calculate particle heating in the detonation barrel.

In this research, a low cost high-velocity air-fuel (HVAF) system was developed and applied for thermal spraying of WC-Co coatings. The resulting coatings were evaluated using optical and scanning electron microscopy (SEM), X-ray diffraction (XRD) and Vickers microhardness measurements. The quality of sprayed WC-Co coatings shows that the developed HVAF system can be an alternative to the existing HVOF with substantial savings on operating costs.

This paper describes an inner diameter HVOF spraying technique and associated tests methods. In the experiments, WC-CoCr was applied to an internal diameter of 150 mm and evaluated using a dedicated pin-on-disk wear test and standard axial fatigue tests. The results are presented and discussed along with the potential for further development of the inner diameter HVOF spraying technique.