Thermal spray coatings have been applied on furnace rolls in continuous annealing lines to improve product quality and prolong roll service life. The most common defects formed on working furnace rolls are oxide pickups. In this study, HVOF sprayed cermet coatings are used to duplicate pickups by reacting with iron and manganese oxides. The reactions are performed in a furnace at 900 °C with inert gas flow. After testing for eight days, large Mn-rich pickups were formed on the coatings while pickups without Mn were very small. Mn was shown to enhance the reaction between the coating and the iron oxide. Pickups from a furnace roll were also investigated and compared with the laboratory samples.

To prepare a dense, defect-free deposit of refractory metals relies not only on the droplets’ state, their temperature and velocity prior to impact on the surface of substrate and/or the precedent deposited layer, but also on the surface temperature of the substrate, whereupon the droplets impact. This paper presents a comprehensive investigation, in which the particles temperature, velocity, and the substrate temperature are studied all-in-one step to understand their influence on the deposit quality. The experimental results make our knowledge of the induction plasma spray of refractory metals process more integrated. Based on our estimation on the effect of all of the three factors, a set of optimized process parameters was established and proved by applying it in producing stationary deposits and coating layers. The results obtained distinguish the induction plasma spray a unique technique, which is ideal to be utilized in refractory metals deposit.

Near-net-shape spray forming reduces the cost and complexity of fabricating certain types of structures. Although such components perform adequately as-sprayed, improvements achieved through alloying, thermal treatments, and additional coating steps are often worth pursuing. In tungsten components, for example, additions of rhenium, nickel, or iron can significantly improve material strength and ductility; thermal treatments such as heat treating and hot isostatic pressing can change and densify microstructures; and coating exposed surfaces can improve environmental compatibility. Such improvements in plasma spray formed refractory metal components are presented in this paper.

Perovskite-type LaMnO 3 powders and coatings have been prepared by a novel technique, the reactive suspension plasma spraying (SPS) using an inductively coupled plasma of about 40 kW plate power and an oxygen plasma sheath gas. Suitable precursor mixtures were found on the basis of solid state reactions, solubility and the phases obtained during the spray process. Best results were achieved by spraying a suspension of fine MnO 2 powder in a saturated ethanol solution of LaCl 3 with a 1:1 molar ratio of La and Mn. Low reactor pressure was helpful in order to diminish the amount of corrosive chlorine compounds in the reactor. As-sprayed coatings and collected powders showed perovskite contents of 70-90%. After a post-treatment with an 80% oxygen plasma an almost pure LaMnO 3 deposit was achieved in the center of the incident plasma jet.