Deposition of TiN, TiC, and DLC Coatings by PACVD

In this chapter, the author studied about titanium nitride (TiN), titanium carbide (TiC), diamond like carbon (DLC) single and multilayer coatings that utilize in harsh environments. These hard coatings were usually produced by the plasma assisted chemical vapor deposition (PACVD) method as a modern technique. PACVD is used to deposit thin coatings for different usages such as computer disc drives, automobile and aerospace parts, surgical/medical instruments and the food industry. The author tried to delineate the state of the performance of different coating systems and layer characteristics that suitable either for laboratory -scales or industrial applications. Mechanical features of these coatings contain the hardness, the toughness, the wear resistance and structural properties that were perused. Consequently, this chapter offers a source of information for those who want to familiarize with the knowledge in the area of materials science of functional coatings that was produced by new plasma-based technologies.

Hybrid Sol-Gel Coatings

The properties and wide application range of organic-inorganic hybrid (O-IH) sol-gel materials have attracted significant attention over the past decades. The combination of organic polymers and inorganic materials in a single-phase provides exceptional possibilities to tailor electrical, optical and mechanical properties concerning diverse applications. This unlimited design concept has led to the development of diverse coatings for several applications such as glasses, and metals to mitigate mechanical abrasion, erosion and corrosion. This class of materials could be easily obtained by sol-gel method at mild synthesis conditions. Furthermore, the large variety of available chemical precursors allows producing a diversity of coatings with tuned mechanical and thermal properties. This chapter will introduce the fundamentals of the sol-gel method to produce O-IH protective thin coatings and discuss the methodologies used to apply these materials onto different metallic substrates for erosion and corrosion protection.

Reactive Plasma Spray

Thermal spraying is a well-known coating technology with many variations in spraying techniques, feedstock materials and substrate materials. These unique variations increased its industrial applicability in different fields, including aerospace, automotive, chemical process, corrosion protection, and medical applications. However, one of the main limitations of thermal spray is the difficulty of depositing several nitride ceramics directly using conventional techniques. This is due to the decomposition of nitride particles under high temperature without a stable melting phase. This chapter presents reactive plasma spraying (RPS) technology as a promising solution for the in situ fabrication of several nitride ceramic coatings. The main attractive prospects of RPS for fabricating nitride coatings are specifically highlighted. Successful development of various high-temperature nitride coatings, such as AlN, Fe4N and Si3N4, are presented. Process optimization, the relationship between reaction and process parameters and the influence on coatings formation are comprehensively discussed.

Slurry Sprayed Mullite Coatings and Their Corrosion Performances

Slurry spray technique (SST) is a distinctive variant among the numerous and already established coating techniques. Functionally graded thermal barrier and environmental barrier coating have been the functionalities developed so far for the process. Among the choice of the various ceramic feedstocks available mullite and partially stabilized zircona have been found suitable and investigated for the coating deposition via SST. This chapter reports the findings of the corrosion studies in simulated industrial corrosive environments and characterization results of the six sets of slurry sprayed mulite-nickel based coatings. Decent protection against coating has been found during the immersion test performed on these coatings for evaluating their corrosion performance. The developed coatings are recommended for use in applications to endure the elevated temperature and inflict corrosion. Thermal cycling test was performed to support the acceptable thermal shock resistance and coating compliance of the developed coatings.

Oxidation Behavior of LTA/YSZ Intermixed Layer Coating

This chapter describes how for power generators like gas turbines and aero engines, the economic and environmental challenges are increasing day by day for producing electricity more efficiently. The efficiency of power generators can be increased by changing its operating conditions like inlet temperature and procedure. Currently, the inlet temperature to the industrial gas turbine is reaching up to 1400°C. Also, in aero engines, the ring temperature reaches around 1550°C. Therefore, the coatings used in aero engine applications undergo short duration thermal cycles at very high temperature. The mean metal temperatures reach around 950°C and can increase up to 1100°C. But in industrial gas turbines, it varies from 800 to 950°C. Operating temperature of industrial gas turbines slowly reaches to maximum and ideally remains constant for thousands of hours, unlike aero engines.

Hardness of Duplex Treated Stainless Steel

This chapter describes how the aim of duplex surface engineering includes chronological application of two surface modification technologies for the production of a surface, with collective properties. Duplex treatment of nitriding and carbonitriding of austenitic stainless steel is of high technical importance owing to its capability to increase hardness, corrosion and wear resistance of treated surface. Duplex treatment has been utilized to enhance the surface mechanical properties of austenitic stainless steel (AISI 304). The microstructure of nitrided surface indicates the development of nitride phases, Fe4N, Fe2N, CrN, Cr2N and γN whereas, duplex treated films shows the formation of FeC, Fe3C, Fe7C3, Cr3C2, Cr7C3, along with nitride phases like Fe3N. Both nitrided and duplex treated samples show the formation of cauliflower like grains. Surface micro hardness of treated substrates has been dependent on the variation of crystallite size and increased by 1.26 times the hardness of nitrided sample and 4.60 times the hardness of the untreated substrates.

Oxidation-Protective Coatings for Carbon-Carbon Composites

Carbon-carbon composites have attractive properties for high-temperature applications but unfortunately, oxidized at a temperature over 500 °C in the air. Various methods used for protection of C-C composites oxidation such as surface treatment, adding inhibitors in the matrix, and outer coating. High-temperature outer coatings are the most effective method to the protection of C-C composites oxidation. Protective coatings should have low oxygen permeability, compatibility with C-C composites, and adherent to the substrate. SiC is a suitable coating but limited in temperature over 1700 °C and below 1100 °C due to evaporation of silica layer and high viscosity of silica layer respectively and so, multilayer coating system used to solve these problems. SiC coating usually is as a bond layer in coating systems.

Thin Coating Deposition by Magnetron Sputtering

Advances in thin-film deposition expose new frontiers to structures and phases that are inaccessible by conventional chemical means and have led to innovative modification of existing materials' properties. Thin-film deposition by magnetron sputtering is highly dependent on ion bombardments; coupled with sublimation of solid target unto the substrate through momentum transfer. It is summarily base on phase change of target material under high-energy influence; corresponding controlled condensation of sputtered atoms on substrate material during which process parameters and growth conditions dictate the pace of the atomic scale processes for thin-film formation. Magnetron sputtering is a state-of-the-art thin film deposition technique versatile for several unique applications, especially in the semiconductor industry. Magnetron sputtering is very novel in its use to achieve low-pressure condition that maximizes and conserve stream of electrons for effective knocking of inert atoms into ions. This ensures the high-energy acquired is not dissipated in gas-phase collisions.

Thermal Barrier Coatings on the Base of Samarium Zirconates

The zirconates of rare earth elements, such as Sm2Zr2O7, can be an alternative material for zirconia modified by yttria (8YSZ) usually used as an insulation layer in thermal barrier coatings (TBC) systems. This chapter describes the morphology of feedstock zirconate powder, internal morphology and selected properties of different samarium zirconate TBC systems. These included: composite TBC coatings of Sm2Zr2O7 + 8YSZ type with different ratio of both used to coatings deposition powders (25/75, 50/50 and 75/25) as well as the TBC of double ceramic layer (DCL) type with an 8YSZ internal layer and an outer layer of Sm2Zr2O7 type, and a monolayer TBC based on Sm2Zr2O7. Another presented subject is related to the oxidation resistance of TBC systems during static oxidation test at temperature 1100°C. In this case, the special emphasis was taken on the characterization of thermally grown oxides (TGO) zone thickness where the most important phenomena related with overall live-time of TBC systems usually take place.

Investigation on Improved-Durability Thermal Barrier Coatings

Concurrent with the development of new generation of gas turbines, many attempts have been made to introduce advanced thermal barrier coatings with lower thermal conductivity and higher temperature stability. Most of the research to improve TBCs performance are based on two general approaches: structural modifications and chemical modifications. In most cases, the improvements in some properties are at the expense of loss of some other properties. Changing in the TBCs architecture and the application of multilayer coatings, consisting of layers with engineered properties based on the requirements, is a solution to achieve a combination of desired properties. In all of these development methods it is to be understood that the principle is reducing the possibility of formation of cracks, but, once formed, all such cracks can grow under and thermal cycles and eventually lead to coating delamination and spallation. Self-healing is the most precious phenomenon to overcome this problem.