This study investigates the development of fatigue failure in steel specimens coated by various spraying methods with and without grit blasting. Commercial titanium powder was deposited on structural steel substrates by low-pressure and portable cold spray as well as plasma and warm spray. Coating samples were subjected to strain-controlled cyclic bending, while monitoring resonant frequency as a measure of accumulated damage. A change in frequency of 4 Hz was chosen as the test-stop with the corresponding cycle count serving as the main indicator of fatigue life. Test results are presented in the paper along with explanations of fatigue mechanisms and process-related factors.

Hydroxyapatite (HA) is preferred for its ability to interact with living bone, resulting in improvements of implant fixation and faster bone healing. In this study, a small amount of silicon dioxide (~ 2wt%) was introduced into HA slurry which was subsequently spray-dried into powder. A silicon modified HA coating was then deposited onto Ti-6Al-4V alloy substrates by atmospheric plasma spraying technology. Scanning electron microscopy (SEM), X-ray diffraction and X-ray photoelectron spectrometry, and Raman spectrometry were employed to investigate the surface chemistry that would directly influence bone forming cell proliferation. Additionally, the adhesive bonding strength of the as-sprayed coatings were specified measured using a universal testing system. The fracture surfaces after tensile test were also investigated by SEM.

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.