Nov_Dec_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | N O V E M B E R / D E C E M B E R 2 0 2 0 5 0 iTSSe TSS iTSSe TSS OBSERVATION OF RESIDUAL STRESS AND FATIGUE BEHAVIOR OF STRUCTURALLY INTEGRATED THERMALLY SPRAYED NICKEL COATINGS Gregory M. Smith, John Saputo, Vladimir Luzin, and Sanjay Sampath Fatigue behavior is strongly correlated with the residual stress statewithin thermal spray coatings, with neutral or com- pressive residual stresses being favorable for fatigue-sensitive applications. However, determination of the coating’s residual stress state is predominately made prior to subjection of the coating to cyclic loading and does not give insight into possi- ble changes to the residual stress state once in service. In this work, high-velocity, oxy-fuel nickel coatings were subjected to a partial fatigue loading regime, via both rotating bend fa- tigue and cantilever fatigue, targeting 99% of the total system fatigue life. Neutron diffraction was used to measure changes between the initial compressive residual stresses and after partial fatigue loading and was compared with the residual stress measurements made via beam curvature techniques during deposition. (Fig. 3) Understanding these effects is mandatory for damage tolerant coating design and wear performance. (Fig. 4) Fig. 4 — Through thickness residual stress profiles of the coatings by Tsui-Clyne analytical model. Substrate is on the left side. COLD SPRAY MCrAlY COATINGS ON SINGLE- CRYSTAL SUPERALLOY USING NITROGEN: PROPERTIES AND ECONOMICS Deliang Leon Guo, Daniel MacDonald, Linruo Zhao, and Bertrand Jodoin Cold spray (CS) has been proven a promising manu- facturing process for the MCrAlY coatings deposition. In this study, NiCoCrAlTaY coatings were deposited on single-crystal nickel-based superalloy (CMSX-4) substrates using the CS tech- nique. Nitrogen and moderate spray parameters were used, and the resulting MCrAlY coatings were compared to coatings sprayed using helium under similar spray conditions. It was found that, contrary to general expectation, favorable coating characteristics were achieved when nitrogen was used. This is attributed to lowdeposition efficiency under the studied spray conditions, resulting in significant particle impingement that promotes overall particle deformation in the coatings sprayed using nitrogen. (Fig. 5) Fig. 5 — Relative cost of CS MCrAlY coatings using helium and nitrogen. Shows benefits of powder recycling for CS using nitrogen. JTST HIGHLIGHTS 14 Fig. 3 — Sample geometry and loading direction for the two different fatigue measurement techniques performed, including RBF (a) and cantilever bending (b). EVALUATION OF RESIDUAL STRESSES AND THEIR INFLUENCE ON CAVITATION EROSION RESISTANCE OF HIGH KINETIC HVOF AND HVAF-SPRAYED WC-CoCr COATINGS Tommi Varis, Tomi Suhonen, Jarmo Laakso, Mika Jokipii, and Petri Vuoristo Thermal spray processes have been developing toward lower particle temperature and higher velocity. Latest genera- tion high-velocity oxygen-fuel (HVOF) and high-velocity air-fu- el (HVAF) can produce very dense coating structures due to the higher kinetic energy typical for these thermal spray process- es. Thermally sprayed coatings usually contain residual stress- es, which are formed by a superposition of thermal mismatch, quenching and, in case of high kinetic energy technologies, peening stresses. These stressesmay have a significant role on the mechanical response and fatigue behavior of the coating.