Search

In the present study, the bi-layer NiCrAlY/Al2O3-40%TiO2 coating was deposited on the three substrates (A-1, T-91, & Superfer800H) by utilizing a plasma spray technique. NiCrAlY was used as a bond coat for ensuring a proper mechanical anchorage of the topcoat (Al2O3-40%TiO2) on to it. The hot corrosion behavior of the coated as well as uncoated substrate was evaluated in an aggressive environment of Na2SO4-60%V2O5 molten salt at 900 °C for 50 cycles (1 h of heating followed by 20 min of cooling at ambient temperature). Thermogravimetric analysis was done to establish the corrosion kinetics of the coated as well as the uncoated substrate. The surface morphology of the as-sprayed and corroded products was analyzed by using a scanning electron microscope (SEM) system, and various phases formed were analyzed by utilizing an x-ray Diffraction (XRD) apparatus. Iron oxide (Fe2O3) is the principal phase formed in the tested uncoated substrate which is non-protective in nature; whereas the presence of Al, and Ti oxides along with some minor oxides of Ni, and Cr were observed in the oxide scale of the tested coated substrate, which are protective and remain stable even at harsh environment condition. The weight gain shown by the coated substrate is less as compared to the uncoated substrate, which indicates the usefulness of the coating.

Erosion is a major problem for the power generation plants for any country. A very high cost induced per annum accounting for the downtime of replacement/repair of boiler components of coal fired power plants due to oxidation and erosion.Thermal spray coating technique is a method used for coating the mechanical components in order to enhance the surface properties of the base material like resistance to corrosion, wearand erosion. In the present study, the cermet powders and coatings (wt% age) are applied on steel substrate with the help of plasma spray gun technique. Techniques like XRD, SEM/EDX and EPMA analysis have been used for characterization of the coatings. These coated materials were subjected to a Pin-on-Disc wear testing.The coated samples have shown almost negligible wear loss as compared to the uncoated samples. Further sliding wear resistance of is almost double of that of coated samples.

The authors propose a method of vibration control based on limiting the maximum axial forces in the active members of an adaptive truss. The actuators simulate linear elastic-perfectly plastic-linear elastic behavior and consume the vibrational energy as work. The method is applicable to both statically determinate as well as indeterminate truss structures. However, for energy efficient control of statically indeterminate trusses, extra actuators may be needed on the redundant bars. An energy formulation relating the various control parameters is derived to get an estimate of the control time. Since the simulation of linear elastic-perfectly plastic-linear elastic behavior requires a piecewise linear control law, a general analytical solution is not possible. Numerical simulation by step-by-step integration is performed to simulate the control of an example truss structure. The problems of application to statically indeterminate trusses and optimal actuator placement are identified for future work.