A new high thermal shock resistant onelayer glass–ceramic coating for industrial and engineering applications

Purpose: A new high thermal stability single layer glass–ceramic coating system designing for applied on various grade of steel alloy has been developed in this work. Design/methodology/approach: The thermal shock resistance, thermal conductivity and thermal expansion of the coating system were evaluated by using suitable standard tests. Some crystalline agents (Lithium oxide Li2O, Titanium oxide TiO2, Zircon ZrSiO4 and Feldspar CaO∙Al2O3∙2SiO2) were add at constant ratio 6% to coating system to evaluate their effects on the resultant coatings. Findings: The results indicate the suitability of these coatings for protection of metal substrate. Also the results show that the properties of resultant coating were hardly affected by composition and concentration of crystalline agent. Research limitations/implications: Coating with lithium oxide has the lowest thermal expansion, which means the highest thermal shock resistance. While, values of thermal conductivity were too close for all types of coating. Originality/value: Generally, the resultant coating properties have been enhanced in all cases; this is associated with the introduce the crystalline agent which lead to the formation of a complex network of crystalline phases.

Surface Modification of Al Components Using Spark Plasma Sintering

A strong push has been observed in the automotive industry to replace current components with high-performance and lightweight materials such as aluminum alloys. Novel monolithic materials such as bulk nanostructured materials, cannot always offer the best performance in hostile environments and often have high manufacturing costs. This has required the development and engineering of processes to allow nanostructured surface functionalization of conventional materials. This processing strategy, similar to the metal-ceramic joining approach, exploits the advantages of both materials while reducing overall manufacturing costs. Spark Plasma Sintering (SPS) will be evaluated as potential a method for manufacturing a nanostructured Al-Si cladding. This novel coating method has a significant advantage over traditional processes in that it forms metallurgical bonds at both the interface and throughout the deposited layer to produce a coating with isotropic properties. The objective of this work is to create a nanostructured eutectic Al-Si feedstock powder and simultaneously consolidate and clad the powder onto a forged aluminum substrate using Spark Plasma Sintering. Results show that after mechanical milling, the aluminum grain size was refined to 47nm. The results also show that SPS is capable of sintering the powder in extremely short sintering times while maintaining nanostructure, and that the heating rate has a large effect on increasing densification rates. Mechanical properties of the resultant coating were also investigated.

Protein hydrophobic dressing on seeds aiming at the delay of undesirable germination

Polymer seed-coatings have been largely tested as an alternative method for preventing diseases and have the potential to be used to control undesirable germination and thereby increasing seed storage. Amongst these, the protein-based coatings can be applied with advantage of forming stable biodegradable and hydrophobic films. Due to their chemical structure, protein dressings act as efficient barriers for water uptake, even when seeds are unavoidable exposed to a moist environment. In this work, the effect of hydrophobic dressings was tested on the germination rate of sugar beet (Beta vulgaris L.) and broccolis (Brassica oleraceae var italic L.) seeds under laboratorial condition. Zein, natural maize (Zea mays L.) proteins extracted from gluten meal, was used as precursor polymers to form the coatings. Seeds were dressed by direct submersion into a zein/ethanol formulation of zein concentration of 3.0 g L-1, followed by natural air drying. The resultant coating has elevated the hydrophobic feature due to the high content amino acids present in the structure of the zein. For both types of seeds an overall delay in sprouting and germination was observed, with a more accentuated reduction on sugar beet germination percentage after eleven days of measurements. The effect on germination rates is understood as the efficiency of the zein coating to form a physical barrier preventing water permeation into the seeds.

Studies of the Flame Spraying of Polymers

Experimental studies of the subsonic combustion process have been conducted in order to determine the quality and economics of polyester, epoxy, urethane, and hybrid polyester-epoxy coatings. Thermally sprayed polymer coatings are of interest to several industries for anti-corrosion applications, including the infrastructural, chemical, automotive, and aircraft industries. Classical experiments were conducted, from which a substantial range of thermal processing conditions and their effect on the resultant coating were obtained. The coatings were characterized and evaluated by a number of techniques, including Knoop microhardness tests, optical metallography, image analysis, and bond strength. Characterization of the coatings yielded thickness, bond strength, hardness, and porosity.

On-Line Diagnostics of Traditional Flame Spraying as a Tool to Increase Reproducibility

Although very frequently used, traditional (low velocity) flame spraying is a much forgotten process. No major research has been performed during the last decade. This paper focuses on the problem of reproducibility of a typical flame gun used with modern automated process equipment. An on-line diagnostic process control tool measuring the temperature, velocity, size and position of the powder in the flame was applied during spraying of abradable coatings of NiCrAl/Bentonite, coatings which are commonly applied to fan and compressor housings of gas turbines. An automated closed loop flame spray unit with mass flowmeters for the oxygen and acetylene gases was used. Influence of different process parameters on the sprayed particles, such as nozzle design, gas flows, and powder feed rate is discussed. Coating properties, such as erosivity, porosity, microstructure and tensile strength, are evaluated. It is demonstrated that even fairly small process changes influence the flame sprayed particles as well as the properties of the resultant coating.