Session BB8.4

2:15 PM BB8.4
PROCESSING EFFECTS ON RESIDUAL STRESS IN PLASMA SPRAYED MOLYBDENUM DEPOSITS. Jiri Matejicek, Sanjay Sampath, Center for Thermal Spray Research, State University of New York, Stony Brook, NY; Paul C. Brand, Henry J. Prask, National Institute of Standards and Technology, Gaithersburg, MD.

Plasma sprayed molybdenum coatings find many applications in automotive industry. Their performance and lifetime can be significantly affected by residual stresses, originating from the manufacturing process. This process involves numerous variables that affect the deposit formation dynamics, microstructure and properties, including residual stress. This study is mainly concerned with the deposition temperature, which has a significant effect on the splat formation, coating build-up, oxidation, strength and stress. Residual stress is particularly influenced by the temperature drop during the particle impact, its adhesion to the substrate and the difference in contraction during the cooling of the coating/substrate couple from deposition to ambient temperature. In this investigation, molybdenum powder was sprayed onto steel, aluminum and copper substrates at three different temperatures, all other parameters being kept constant. Microstructure of the coatings was examined and a complex characterization of their properties was conducted. Residual stresses in thin and thick coatings were measured using x-ray and neutron diffraction, respectively. Based on the experimental results, the relative magnitude of quenching and thermal mismatch stress can be assessed and correlation to processing and microstructure can be drawn.