In this paper, it is shown that mixing metal powders can lead to improvements in cold sprayability (i.e. increases in the deposition efficiency and decreases in the porosity) of the ‘matrix’ powder. This finding is illustrated with the following ‘binary’ mixtures: Ti – 6Al-4 V and commercial purity Ti; stainless steel and iron; spherical tantalum with irregular tantalum and two types of spherical tantalum with different characteristics. It is shown that a critical addition can significantly influence cold sprayability, but above this, there is little change in cold sprayability. Hardness differences are considered to be the first order influence, but differences in particle sizes and morphology may also be contributing factors.

Two kinds of thermal barrier coatings with NiCoCrAlY bond coatings (BCs) deposited by electron beam-physical vapor deposition (EB-PVD) and high velocity oxy-fuel thermal spraying (HVOF), respectively, as well as their top 8wt.%Y 2 O 3 -ZrO 2 (YSZ) ceramic layers deposited in one batch by EB-PVD were prepared on near-α titanium alloys. The field emission scanning electronic microscopy and microhardness indentation are used in comparatively study of microstructures, microhardness of samples. Cracking modes and crack characteristics in TBCs are investigated after thermal cycling in atmosphere, along with the discussion of roles of residual stresses, bonding strengths and mechanical properties of bond coatings in different failure extents. It is found that morphologies of BCs deposited by different methods (EB-PVD and HVOF) result in the different microstructures and microhardness of their upper YSZ. The denser and more homogeneous BC prepared by EB-PVD leads to the YSZ with finer and denser columnar clusters and higher microhardness, and the inhomogeneous and porous latter results in the upper YSZ with coarser and loosely bonded columnar grains and lower microhardness, and the TBC with BC deposited by EB-PVD is more protective, which is synthetically induced by residual stresses, bonding strengths and mechanical properties of bond coatings.

This paper investigates the influence of spraying current and gun transverse speed on the characteristics of the hydroxyapatite (HA) and Ti-6A1-4V composite coatings. Two different kinds of feedstock are being used; HA and Ti-6A1-4V in the ratio of 80 v/t. %: 20 wt. % and 50 wt. %: 50 wt. % respectively. The paper investigates the influence of the plasma spray currents at 600 A, 800 A, and 1000 A and the influence of the feed speeds of the spray gun at 250 mm/s, 500 mm/s, and 750 mm/s. It examines the powders or coatings using an Instron machine, XRD, and scanning electron microscopy. It is found that a spraying current of l000 A, relative to 600 A and 800 A, gives a coating that is less porous and composed of a well-splayed structure. It also yields the highest bond strength among the coatings. Paper includes a German-language abstract.