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

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

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.</jats:p

High temperature erosion behavior of plasma sprayed Al₂O₃ coating on AISI-304 stainless steel

Purpose In the present study, Al2O3 coatings were deposited on stainless steel AISI-304 material by using atmospheric plasma spraying technique to combat high temperature solid particle erosion. The present aims at the performance analysis of Al2O3 coatings at high temperature conditions. Design/methodology/approach The erosion studies were carried out at a temperature of 400°C by using a hot air-jet erosion tester for 30° and 90° impingement angles. The possible erosion mechanisms were analyzed from scanning electron microscope (SEM) micrographs. Surface characterization of the powder and coatings were conducted by using an X-ray diffractometer, SEM, equipped with an energy dispersive X-ray analyzer. The porosity, surface roughness and micro-hardness of the as-sprayed coating were measured. This paper discusses outcomes of the commonly used thermal spray technology, namely, the plasma spray method to provide protection against erosion. Findings The plasma spraying method was used to successfully deposit Al2O3 coating onto the AISI 304 substrate material. Detailed microstructural and mechanical investigations were carried out to understand the structure-property correlations. Major findings were summarized as under: the erosive wear test results indicate that the plasma sprayed coating could protect the substrate at both 30° and 90° impact angles. The coating shows better resistance at an impact angle of 30° compared with 90°, which is related to the pinning and shielding effect of the alumina particle. The major erosion wear mechanisms of Al2O3 coating were micro-cutting, micro-ploughing, splat removal and detachment of Al2O3 hard particles. Originality/value In the current study, the authors have followed the standard testing method of hot air jet erosion test as per American society for testing of materials G76-02 standard and reported the erosion behavior of the eroded samples. The coating was not removed at all even after the erosion test duration i.e. 10 min. The erosion test was continued till 3 h to understand the evolution of coatings and the same has been explained in the erosion mechanism. The outcome of the present study may be used to minimize the high temperature erosion of AISI-304 substrate. </jats:sec

A review on the processing of various coating materials using surface modification techniques for high-temperature solid particle erosion applications

In 21st century with the advent of industrial revolution 4.0, the future manufacturing and power generation industries will scale new heights. The focus of researchers and engineers is on higher operating plant/gas turbine temperatures and more efficient plants with minimal breakdowns. This is possible practically due to the development of new heat/corrosion/erosion resistant materials using different surface engineering approaches. The main focus of this article is to review the solid particle erosion behavior of conventional, nano materials and high entropy alloys under elevated temperatures and the summarized analysis helps the researchers in selecting the appropriate composition, coating methods and erosion resistant materials to combat the erosion at elevated temperatures, so that life of components can be improved. In addition to this future perspective is also discussed

HIGH-TEMPERATURE OXIDATION AND EROSION RESISTANCE OF NI-BASED THERMALLY-SPRAYED COATINGS USED IN POWER GENERATION MACHINERY: A REVIEW

The life of the components operating under various high-temperature environments decreases due to the activation of different failure mechanisms. High-temperature oxidation and erosion are the two prominent mechanisms that lead to the degradation of materials, resulting in the premature failure of the components. This paper has emphasized the failure and performance analysis of nickel-based coatings formulated by using different thermal spraying techniques. Nickel-based coatings like Ni–Cr, Ni3Al, Alloy-718, NiCrAlY, NiCrBSi and Ni-based composite coatings showed excellent resistance against the high-temperature conditions. This study helps to select specific thermal spray techniques and coating composition against high-temperature erosion and oxidation conditions. </jats:p

Influence of heat treatment on surface properties of HVOF deposited WC and Ni-based powder coatings: a review

Abstract Post-spray treatments have recently been popular as a means of improving the overall quality of thermally sprayed coatings, particularly those done using the HVOF technique. Thermally assisted surface treatment of deposited coatings is an effective way to improve the characteristics of coated components for specific applications. The tribomechanical properties of post-treated WC and Ni-based coatings deposited with high-velocity oxy-fuel (HVOF) technique have been addressed. The structure-property correlations concerning the as-sprayed and post-treated coatings have been considered to understand the various mechanisms responsible for improved performance in terms of wear and corrosion resistance. The recent advancement in the post-treatments such as post-processing using microwave hybrid heating, laser-assisted processing and Stationary friction processing have been incorporated in the current review. Comparative studies have been presented to understand the structure-property relationship and performance of WC and Ni-based HVOF sprayed coatings with the help of various characterization techniques in this review article.</jats:p