Corrosion and wear resistant advanced coatings for typical engineering applications

Editoria

High Temperature Oxidation and Wear Resistant Bi-Layer Coating for Turbocharger Housing

An upsurge in the demand of higher power generation has been observed in the last few decades. Consequently, the mechanical components of power generation are forced to operate in the extreme working conditions for longer duration, which results in the accelerated wear and corrosion of the material. Conventional material such as grey cast iron (GCI) is a preferred material of components used for power generation at high temperature. Grey cast iron exhibits poor wear and corrosion resistance at high temperature. On the other hand, an advanced material such as Alloy-718 is capable to withstand the high-temperature wear and oxidation for prolonged duration of time. In the current research, high temperature corrosion and erosive wear performance of grey cast iron (GCI) components has been enhanced by depositing a bi-layerAlloy-718/NiCrAlY coating by using high velocity oxy-fuel (HVOF) thermal spray process. Furthermore, the high temperature corrosion and erosion behaviour of GCI substrate and the deposited coating has been discussed. The various characterization techniques such as scanning electron microscopy (SEM) X-ray diffraction, and Vickers micro-hardness testing were conducted for the GCI substrate and Alloy-718 coating, respectively. The Alloy-718 coting showed the increased resistance against high-temperature erosion and oxidation, which can be attributed to its good bonding with the substrate, high hardness and formation of protective phases at high-temperature

Surface protection of SS-316L with boron nitride based thin films using radio frequency magnetron sputtering technique

In the present work, the radio frequency (RF) magnetron sputtering process was used to develop boron nitride thin films on 316L stainless steel. The target material used in the experiment was a hexagonal boron nitride (c-BN) target. The deposition was performed in three different Ar and N2 system mixing regimes. The composition and morphology of the coating developed at various N2 and Ar plasma ratios were investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The electrochemical corrosion test was used to investigate the boron nitride coating\u27s corrosion behaviour. The goal was to study the changes in the ratio of N2 and Ar during the process and to understand the structure of cubic boron nitride (c-BN) coatings. Increased microstruc­ture uniformity and further c-BN step creation with different quantities (Q) QAr/QN2 = 2 imply a fundamental strategy for creating improved cubic boron nitride films

Bioactivity and corrosion analysis of thermally sprayed hydroxyapatite based coatings

Metallic biomaterials have been used to repair and replace human body parts because of their excellent biocompatibility, strong corrosion resistance, and high mechanical properties. A ceramic biomaterial that is highly suitable for coating on metallic biomaterials is hydroxyapatite. This is because it is biocompatible with synthetic and natural bone tissue. There has been a growing interest in HAp-based coatings using thermal spray techniques to enhance the crystallinity and adhesion quality and produce a dense coating of metallic biomaterials. Thermally sprayed coating material has been studied and reviewed in detail in the bioactivity analysis and electro-corrosion analysis. Furthermore, the bioactivity of HAp coatings is determined by their ability to promote bone formation and osseointegration and a valuable understanding of the mechanisms and current advancements in bioactivity. Additionally, the corrosion behaviour of thermally sprayed HAp coatings under simulated conditions has been reviewed

Wear Characteristics of Ni-WC Powder Deposited by Using a Microwave Route on Mild Steel

In the present research work, Ni-WC powder was deposited on mild steel using a microwave applicator. Deposited clad has a thickness of 0.5 mm and deposition time taken for coating was 15 minutes for each sample size. The developed layer on the substrate was analysed through several testing techniques include mechanical characterization by the Vickers hardness test and a wear test on the Pin-on disc apparatus according to ASTM-G99 standard. Furthermore, micro structural characterization was done by using scanning electron microscopy technique and it has shown proper bonding between powder and substrate. Coating showed excellent results in terms of hardness and wear resistance as compared to base material mils steel. The pullout, scoring and abrasion were the responsible wear mechanisms in the substrate and clad.</jats:p

Understanding cold spray technology for hydroxyapatite deposition

The standard method for applying hydroxyapatite (HAp) coatings to biomedical implants is plasma spraying. However, due to the high temperature of the plasma, these coatings frequently experience negative effects like evaporation, phase change, de-bonding, gas release, and residual stresses. This paper summarizes a revolutionary technique known as a cold spray (CS), which allows HAp coatings to be applied at temperatures well below their melting point. CS has several advantages over conventional high-temperature technologies, and it seems to be approaching parity with other older methods. When applied using the CS approach, the HAp coatings enhance bioactivity, increase corrosion resistance, and main­tain the characteristics of calcium phosphate ceramics. This study aims to give a concise and comprehensive overview of HAp-based materials, including substituted-HAp and HAp/poly­mer composites, and their applications in bone tissue engineering. To better understand the advantages of CS technology, a comparison of CS, high-velocity oxy-fuel (HVOF), and plasma spray is given at the end. The perspective and difficulties were also highlighted

A REVIEW ON THE INFLUENCE OF PROCESS PARAMETERS AND HEAT TREATMENT ON THE CORROSION PERFORMANCE OF NI-BASED THERMAL SPRAY COATINGS

Various typical engineering components fail from surface under aggressive conditions like oxidation and hot corrosion. This paper is focused on the responsible failure mechanism of oxidation and hot corrosion. The surface properties like corrosion resistance can be enhanced by introducing a layer of Ni-based materials by using thermal coating techniques. The coatings developed by using processes like high velocity oxy-fuel, plasma spray and cold spray exhibits some surface defects like porosity, surface roughness and un-melted particles. Such defects can be further minimized by using optimization of process parameters and various heat treatment processes. The current study is restricted to the analysis of Ni-based coatings developed using high velocity oxy-fuel, plasma spray and cold spray process. In this paper, the optimization of various process parameters along with heat treatments has been discussed in regard to the tailoring of microstructure and the mechanical properties of the developed coatings. </jats:p

Advancements in ceramic-coated metals: Enhancing thermal spray coatings for improved performance in aerospace applications using surface treatments

Ceramic-coated metals which have superior physical and mechanical properties especially chemical and environmental deterioration resistance and high thermal stability were used formerly in many commercial applications. Thermal spray coatings play a significant role in aerospace, especially because when applied they import positive value on wear and thermal barriers in aspects of an engine part hence better performance and durability on the parts used. Knowledge enhancement of some regulatory parameters of the grit blasting on substrate coat is the objective of this work. From the above results it can be concluded that for the overlay deposit of CoNiCrAlY coatings the CFS appears to be an economic solution which also minimizes the hardware. Oxidation of the particles of powder, which are used in flight, leads to the reduction of tensile strength and the performance characteristics with respect to high-temperature stresses. It has good adhesion and the wear resistance, corrosion and high-temperature stresses of the coatings that are made are improved. Described coatings microstructures in the said coatings were investigated using SEM imaging with elemental mapping of details of their compositions which augmented the results of the adhesive bond strength tests coupled with Vickers hardness tests for the qualitative evaluation of their physical–mechanical properties. Therefore, the result gotten from these micrographs can intern be used to optimize the thermal spray process to enhance on the performance as well as the life span of the coated coatings. From the above-described post processing treatments the application of these treatments increases the service capability of the splats and substrate surface; and that the adhesion of the post processing treatments to the splats and substrate surface is also increased. It therefore adds to the ongoing process of improvement of these processes and there uses by identifying areas where more research can be done