In the world, automobile rim production is carried out in a repeatable quality with low pressure die casting process. Traditional die coatings used to separate molds on casting mold surfaces cause significant losses in production due to their weak strength. The applicability of an alternative mold coating application with thermal sprayings has been examined in this study. MgO-ZrO 2 based ceramic thermal barrier coatings are deposited on the mold surfaces by flexicord spray method.

Thermally sprayed Al 2 O 3 -TiO 2 coatings were in the area of interest over the last decade because they showed improved wear properties over conventional coatings. In this study, flexicord flame spray gun was used to deposit Al 2 O 3 -TiO 2 coatings at different spray parameters. The microstructural morphology variation and phase transformation of coatings were investigated. In addition, as one of the most important properties for ceramic coatings, hardness, solid particle abrasive wear resistance of coatings were measured before and after heat treated condition. Test results show that the higher mechanical properties and wear resistance by the heat treatment at elevated temperatures.

This study assesses the abrasive wear resistance of Cr 3 C 2 -NiCr coatings produced by HVOF spraying. Abrasion tests were conducted in a three-body solid-particle rubber-wheel test rig using silica and alumina grits under different loads. The results indicate that abrasion performance is controlled by cohesion between splats, which can be further improved. The removal of carbide particles was the main wear mechanism and is controlled by the content and size of the Cr 3 C 2 particles. It is shown that the abrasive wear resistance of carbide-based cermet coatings is significantly higher than that of mild steel.

Plasma sprayed yttria stabilized zirconia (YSZ) coatings are being increasingly used as thermal barrier coatings(TBCs) for gas turbine parts. However oxidation problems are critical for durability of TBC. Al 2 O 3 addition to YSZ is considered as an oxygen barrier microstructure at elevated temperature. Therefore it helps to the growth rate of the thermally grown oxide layer between top coat and bond coat. Spray properties and rapid solidification determine the final characteristics of the coating. Plasma current, plasma gas flow rate and spray distance factors have main effect on occurrence of microstructure. Therefore plasma spray parameter optimisation is required for TBC manufacturing. Statistical designs of experiments have been shown to provide efficient approaches to systematically investigate the process parameters of plasma spray process. In this study Al 2 O 3 -YSZ particle composite TBC deposited with different plasma spray process parameters by using Taguchi method for optimisation.

With the modification of plasma spray parameters, porosity ratio of top coat can control along the cross-section. This improves the thermal cycle resistance and decrease the thermal conductivity. Plasma sprayed ZrO 2 /8 wt.–% Y 2 O 3 –NiCrAlY TBC systems which have different porosity (%8-12) and range of 250-350µm thicknesses of top coats, during thermal cycling tests with different hold times at 1350 °C have been performed. The main failure modes: delamination cracking, TGO growth rate and phase transformation are strongly dependent on the hold temperature and time. The correlation between TBC thermal cycle lifetimes and duration of high temperature hold time per cycle is shown and discussed with depending on thickness and porosity ratio.

Biocompatibility of hydroxyapatite (HAp) coatings have led to its use in a wide range of applications in both dentistry and orthopaedics. The plasma spraying method is the most commonly used method for the production of Hap (Ca 5 (PO 4 ) 3 OH) coatings on Ti alloys. When HAp is injected into the plasma jet, several phases can coexist under the effect of a temperature gradient occurring in the bulk of the particle. The amounts of residual compounds, amorphous and recrystallized phases are related to the conditions of spraying such as gas flow rates, feed rate, spray distance, plasma current and cooling effect. Plasma-sprayed HAp coatings were analyzed by X-ray diffraction and electron microscopy.

WC-CoCr coatings are deposited by HVOF process for improving surface resistance of low alloyed steels. In this study we examined the wear characteristics of WC-CoCr coatings on low alloyed steel substrate under different test conditions, using a sliding wear test unit with abrasive ball. In experimental studies discussed the effects of test load, temperature, work medium and sliding distance on the wear characteristics of coatings. Weight loss, wear track depth and width were observed . It was found that the weight loss of coatings increased in dry medium conditions. Wear weight loss was significantly reduced in lubricated condition due to decreasing friction. The wear track surface profile changed with lubrication and increasing temperature in test conditions. Under the base oil lubricated conditions the WC-CoCr coating performed well.

Ductile iron pipes (DIP) have been used worldwide since 1960s for water transmission and distribution mains. By 1979, ductile iron pipe largely replaced cast iron as the predominant material in water industry. Zn and Zn/Al 85/15 coatings applied by thermal spray technique are used for the protection of the ductile iron pipe against corrosion in heterogeneous soil conditions. In this study, heat treated and non-heat treated ductile iron pipe samples were coated with Zn and Zn/Al 85/15 in optimum spray parameters by twin wire electric arc (TWEA) spraying technique. The coatings were investigated by optical microscopy, scanning electron microscopy (SEM), and analyzed by energy dispersive spectrometer (EDS). Both Zn and Zn/Al 85/15 coatings showed fairly good lamellar structure with acceptable amount of internal porosities and oxides. Annealing oxides available on pipe surface helped the bonding of coatings. The protection performance of the coatings was compared with accelerated corrosion (salt spray) test according to the ASTM B 117 and corrosion products were analyzed by SEM and EDS technique. Salt spray test results showed that Zn/Al 85/15 coatings have better corrosion resistance than Zn coatings and annealing oxide on ductile iron pipe acts as a good corrosion resistant protective layer.

Plasma-sprayed thermal barrier coating (TBC) systems are widely used in gas turbines blades in order to increase turbine entry temperature (TET) with better efficiency. Yttria stabilized zirconia (YSZ) has been usually chosen as the top thermal barrier coating material because of its low thermal conductivity, high thermal expansion coefficient and good corrosion resistance. However as a new candidate commercial TBC material, ceria stabilized zirconia (CSZ) currently looks to be promising. Ceria and ceria based ceramics show an outstanding potential for use at temperatures exceeding 1200 °C. CSZ coatings do not only have high temperature stability, good corrosion resistance and high fracture toughness but also lower thermal conductivity and higher thermal expansion coefficient than YSZ coatings. The sintering and phase transformation characteristics of both ceramic thermal barrier coatings under high temperature conditions are complex phenomena. In this paper, microstructural differences, sintering behaviours (1200 oC, 10h, 25h and 50h) and phase transformations of the plasma sprayed ceria stabilized zirconia (CSZ: ZrO 2 –2.5 wt.%Y 2 O 3 – 25 wt.%CeO 2 ) and conventional yttria stabilized zirconia (YSZ; ZrO 2 –8 wt.%Y 2 O 3 ) coatings and their powder materials have been investigated and compared using thermal analysis techniques, XRD and scanning electron microscope.

Zircon (ZrSiO 4 ) is a technologically important oxide ceramic material known for its high refractoriness and chemical stability. It shows excellent thermal shock resistance as a result of its very low thermal expansion coefficient and a low heat conductivity coefficient. Plasma spraying is a convenient method to produce large area coatings with high growth rates, necessary for many applications. ZrSiO 4 is among the least expensive spraying materials for refractory applications. In this study, a single-step process was used to prepare mullite/zirconia ceramic composites by plasma spraying zircon/alumina mixtures. Mixtures of ZrSiO 4 and Al 2 O 3 powders with Al 2 O 3 to SiO 2 molar ratios of 3:2 were milled for 2 h in a zirconia medium using a ball mill. The as–milled powders were dried in the furnace and sintered at 1300 and 1350 °C for 2h then crushed to a size less than 100 μm. The powders were sprayed by an atmospheric plasma spray gun (Metco 3MB) using C/C+SiC ceramic matrix composite substrates. Scanning electron microscopy (SEM) was used to analyze the microstructures of the powders and plasma coatings. The phase composition analysis of the powder showed the presence of alumina and zircon. After plasma coating, alumina, zircon, and zirconia phases were determined.

Twin wire arc sprayed Zn, Al and Zn/Al 85/15 coatings were investigated for comparison of their corrosion resistance, electrochemical behavior. The Zn, Al and Zn/Al 85/15 coatings possess prominent electrochemical passivation behavior. Oxide formation mainly onto the coating surfaces were identified with energy-dispersive X-ray analysis and were believed to be responsible for the passivation phenomena observed in the electrochemical polarization. Zn and Al are more negative in electrochemical potential than iron. Zn coatings act as a sacrificial anode and providing cathodic protection. Aluminum shows passive corrosion protection according to stable oxide layer occurs on coating surface. Zn/Al 85/15 coating show two corrosion protection mechanisms together. In this study, steel samples were coated with Zn, Al and Zn/Al 85/15 in optimum conditions by wire arc spraying technique. These coatings were investigated behaviors of polarization and corrosion resistance with electrochemical test.

Zn and Zn/Al coatings were manufactured by using twin wire arc spray (TWEA) system under various gas pressure and current. Microstructure, hardness, surface roughness and adhesion strength of the coatings were investigated by using standard characterization methods. Test results show that increasing atomizing gas pressure increased mechanical properties and surface quality. The process current had an important role on microstructural, mechanical properties and surface quality.

Thermal barrier coatings (TBCs) were deposited by an Air Plasma Spraying (APS) technique. The coating comprised of YSZ – 0, 20, 50 and 80 wt % Al 2 O 3 ; NiCrAlY bond coat; and AISI 304L stainless steels substrate. Thermal shock tests were performed over the specimens, at 1000 °C and 1200 °C for 5 min and then forced air quenching. The samples were directly pushed into a tube furnace at 1000 °C and 1200 °C. The results were prominent in forced air quenching tests at 1000 °C , where the lives of the TBCs were observed more than 66 cycles. It was noticed that with increase of Al 2 O 3 content the thermal shock life of the specimens decreased. Further, the coating roughness decreased by Al 2 O 3 addition. It was observed that with decrease in coating roughness, the thermal shock life decreased slightly.