NEURAL NETWORK ANALYSIS FOR DEPOSITION OF NICKEL-ALUMINIDE COATINGS ON STEEL BY PLASMA SPRAYING
Nickel-aluminides are used in thermal spray applications mostly as bond-coat materials, where their function is two-fold: to minimize the thermo-mechanical stresses at the substrate-coating interface arising out of thermal expansion mismatch of the metal substrate and ceramic top layer and secondly to promote coating adhesion. This paper describes the deposition of nickel aluminide coatings on mild steel substrates. A computational technique (ANN analysis) is used to predict the rate of coating deposition under various operational conditions. Prediction of deposition efficiency is significant as it gives an idea about the effectiveness of the spraying technique as well as about the coatability of the material under investigation. This technique involves database training to predict property parameter evolutions in process having large number of interdependent variables such as in the case of plasma spray coating deposition. This paper presents the database construction, implementation protocol and also the set of predicted results related to the deposition efficiency of nickel-aluminide coating. It is seen that the deposition rate depends largely on the plasma arc current, arc voltage etc. The neural network analysis gives an oversight on the parameter inter-dependencies and of the effect of the individual process variable on the efficiency of coating deposition.
Evaluation of NiAl and NiAl-B deposited by vacuum plasma spray
Nickel aluminide, NiAl, has potential for high-temperature structural applications because of its high melting temperature, low density, high elastic modulus, and excellent oxidation resistance. However, inadequate room-temperature ductility and low strength at high temperatures limit the use of NiAl for practical service. An added limitation is the difficulty of forming this intermetallic compound. Plasma spray forming is suggested to produce NiAl in useful shapes and forms. In this study, vacuum plasma spray has been used to produce coatings and free-standing forms of NiAl and NiAl microalloyed with boron (NiAI-B). This research focuses on an investigation of the structures and properties of the as-sprayed deposits. Preliminary analysis reveals that the deposits formed by vacuum plasma spray are very dense and essentially oxide free. The as-received aluminide powders and the sprayed deposits have the same phase structure. Tests also indicate that the mechanical properties achieved by plasma spray are comparable to those achieved by other processing techniques.
Analysis of a coaxial-to-waveguide adaptor including a discended probe and a tuning post
A field matching analysis of a coaxial-to-waveguide adaptor incorporating a disc-ended probe and a tuning post is presented. In this analysis, the tuning post is considered as a short-circuited second probe. A computer algorithm for calculating the input impedance of this structure is developed. This algorithm is used to investigate and improve the operation of a commercially available coaxial-to-waveguide adaptor. >