In Situ Temperature Measurement Using Embedded Micro-Thermocouples in Vacuum Plasma Sprayed Multi-Layered Structures

1998 ◽  
Author(s):  
C. Verdy ◽  
B. Serio ◽  
C. Coddet
Keyword(s):  
Thermal Spray ◽  
Thermal Spray Coatings ◽  
Spray Coatings ◽  
Spray Process ◽  
Vacuum Plasma ◽  
Copper Coatings ◽  
Plasma Sprayed ◽  
Spraying Process ◽  
Infrared Pyrometer

Abstract The integration of thermocouples into thermal spray deposits and especially into vacuum thermal spray coatings could provide temperature monitoring between the substrate and the coating or between two different coatings during the spray process and later during post treatments and service life. Thermocouples of 251µm in diameter were made using Chromel® and Alumel® wires. Electrical insulation was obtained using a ceramic cement. Astroloy and Copper coatings were successfully sprayed over these sensors and the temperature given by an embedded thermocouple was compared to the response of an infrared pyrometer during the spraying process.

The Ultimate Spray Booth

1997 ◽  
Author(s):  
L. Pejryd ◽  
J. Wigren ◽  
N. Hanner
Keyword(s):  
Thermal Spray ◽  
Thermal Spraying ◽  
Thermal Spray Coatings ◽  
Design Element ◽  
Production Flow ◽  
Statistical Process ◽  
Spray Coatings ◽  
Spray Process ◽  
Spray Booth ◽  
On Line

Abstract Reproducibility is a current challenge for the thermal spray industry. Reproducibility associated problems represent a large cost every year not only in terms of rejections and rework, but also in costs for destructive testing and decreased production flow. Thermal spray coatings are moving in the direction of being considered only as a "band aid" to becoming a design element. One of the prerequisites for such a development is an increase in reproducibility for thermal spray coatings. The purpose of this paper is to outline a vision aiming in the direction of a future "ultimate spray booth", where thermal spraying is as reproducible and reliable as machining, grinding or other production processes. A way to increase reproducibility and reliability in the future spray shop involves utilising major parts of IT - technology. This also includes active co-operation design-production in the pre-spray process. This paper will deal with areas such as: operation drawings and lists through multimedia techniques, education programs for operators and designers through multimedia techniques, CAD/CAM, Off-line programming and simulation, On-line diagnostics of flame (particle diagnostics) and coating (temperature & Acoustic emission measurements), on-line Statistical Process Control and Knowledge Based System techniques.

An ASM Recommended Practice for Evaluation of Young’s Modulus and Poisson’s Ratio of Thermal Spray Coatings Bonded to a Substrate

2000 ◽  
Author(s):  
J.R. Shadley ◽  
E.F. Rybicki ◽  
Y. Xiong ◽  
R.T.R. McGrann ◽  
A.C. Savarimuthu
Keyword(s):  
Young’S Modulus ◽  
Thermal Spray ◽  
Poisson’S Ratio ◽  
Young's Modulus ◽  
Thermal Spray Coatings ◽  
Poisson's Ratio ◽  
Spray Coatings ◽  
Recommended Practices ◽  
International Thermal Spray

Abstract In situ values of Young's modulus and Poisson's ratio for thermal spray coatings are needed to evaluate properties and characteristics of thermal spray coatings such as residual stresses, in-service stresses, bond strength, fracture toughness, and fatigue crack growth rates. It is important to have methods documented in detail so that people can follow the document and use the methods. Such a document requires more pages than are allowed in conference proceeding and journal papers. Thus, Recommended Practices and Standards describing these methods are needed. Currently, there is not a recommended practice or standard for evaluating Young's modulus and Poisson's ratio for thermal spray coatings. The ASM International Thermal Spray Society has recognized this need and formed a committee on Recommended Practices for Thermal Spray Coatings. This paper describes one of the recommended practices being written by the Mechanical Properties Evaluation Subcommittee of the Recommended Practices Committee. The specimen is a coated substrate in the form of a cantilever beam. The method is easy to use and inexpensive. The equipment needed is a vise or clamping fixture, strain gages, a strain indicator, a micrometer, a ruler, a hanger, and a set of weights. The specimen is easy to machine and spray. The loading is easy to apply and remains constant during readings. The method can be used to evaluate Young's modulus and Poisson's ratio in tension or compression. A description of the method, a verification, and a sensitivity analysis was done and published in Reference [1]. Some of the details of implementing the method and the data sheet are presented here.

Characterization of Thermal Spray Coatings Used for Dimensional Restoration

2000 ◽  
Author(s):  
R.T.R. McGrann ◽  
J. Kim ◽  
J.R. Shadley ◽  
E.F. Rybicki ◽  
N.-G. Ingesten
Keyword(s):  
Residual Stress ◽  
Bond Strength ◽  
Thermal Spray ◽  
Thermal Spray Coatings ◽  
Tensile Bond Strength ◽  
Spray Angle ◽  
Metallographic Examination ◽  
Substrate Interface ◽  
Spray Coatings ◽  
Spray Process

Abstract Thick thermal spray coatings are used to repair worn parts during aircraft overhaul. The thermal spray coating is used to restore a part to its original dimensions. Characteristics of the as-applied coating that affect the performance of thermal sprayed parts are the residual stress in the coating, the tensile bond strength, the amount of porosity, oxides and impurities near the coating/substrate interface, and the hardness of the coating. An understanding of the relation of these coating characteristics to process variables such as the material used for the coating, spray process, spray angle, and thickness of the applied material is needed. In this paper, four thermal spray coatings, Ni5Al, Ni5Al-atomized, (NiCr)6Al, and Inco 718, on a substrate of Hastelloy X are investigated. These materials are applied using two different thermal spray application processes: plasma spray and High Velocity Oxy-Fuel (HVOF). Spray angles of 90° and 45° are used during spraying. The nominal thickness of the applied coatings ranges from 0.4 mm to 1.8 mm. The thermal spray coatings are evaluated in four types of tests. Residual stresses in the coatings and substrate are evaluated using the modified layer removal method. A tensile bond strength test is performed. Metallographic examination is used to determine the porosity and content of oxides and bond zone impurities (percent) of the applied materials. In addition, the hardness of the coating is measured. For the materials and conditions investigated, it is found that residual stress varies with each of the four process parameters. The bond strength for plasma sprayed coatings is related to the type of material and possibly to the coating thickness. The percent porosity varies with coating material, but, for Ni5Al, it does not depend on application process. Oxide content, as a percentage, varies with material and process, but not with spray angle and thickness. The percentage of impurities near the coating/substrate interface varies with process and, for the specimens that were coated using the HVOF process, with thickness. The hardness of the coating was found to vary with material and spray process. For three of the four coatings, hardness increases with thickness but, for Inco 718, hardness decreases as thickness increases.

Prediction of Residual Stress and Damage in Thermal Spray Coatings Using Hybrid Computational Approach

2018 ◽  
Author(s):  
Abba A. Abubakar ◽  
Abul Fazal M. Arif ◽  
Khaled S. Al-Athel ◽  
S. Sohail Akhtar
Keyword(s):  
Residual Stress ◽  
Thermal Spray ◽  
Point Cloud ◽  
Hybrid Approach ◽  
Computational Approach ◽  
Thermal Spray Coatings ◽  
Element Analysis ◽  
Influence Of Process Parameters ◽  
Spray Coatings ◽  
Spray Process

Due to the multilayered pattern of coating deposition, numerical prediction of residual stress and damage in thermal spray coatings (TSCs) has been challenging. Several numerical approaches previously used failed to capture essential aspects such as deposition stress build-up, presence of heterogeneities, and influence of process parameters. In the present study, a hybrid computational approach which combines “point cloud” (PC) and finite elements (FE) has been used to model the spray process as well as the evolution of residual stress and damage. Smooth particle hydrodynamics (SPH) is used to model multiple droplets deposition and associated deformation on PC. Then, several recent algorithms (for point cloud processing) are used to convert the deformed droplets (in form of PC) into FE domains (i.e. splats). The FE mesh of deposited splats is used for thermo-mechanical finite element analysis where the evolution of temperature, residual stress and damage is predicted on simulated coating microstructure. By comparing our numerical results with that of previous works, the hybrid approach has been found to be a viable tool for quantitative assessment of residual stresses and failure in TSCs.

Evaluation of Failure Micromechanisms of Advanced Thermal Spray Coatings by In Situ Experiment

2014 ◽  
Vol 606 ◽  
pp. 187-190 ◽  
Author(s):  
Radek Mušálek ◽  
Catalina Taltavull ◽  
Antonio Julio Lopez Galisteo ◽  
Nicholas Curry
Keyword(s):  
Thermal Spray ◽  
Thermal Spray Coatings ◽  
Three Point Bending ◽  
Spray Coatings ◽  
Barrier Coating ◽  
Failure Evolution ◽  
Inhomogeneous Character ◽  
Coating Microstructure ◽  
Service Conditions

Identification of failure mechanisms of thermal spray coatings by means of traditional fractography of failed parts is often troublesome. Reason for this is a highly inhomogeneous character of the coating microstructure and harsh in-service conditions which may hinder evidentiary fractographic marks. In this study, failure evolution of advanced thermal barrier coating (TBC) prepared by plasma spraying was studied in-situ at high magnification in a scanning electron microscope under well-defined laboratory conditions of three-point bending (3PB).

In-Situ Observation and Ae Analysis of Microscopic Fracture Process of Thermal Spray Coatings

1998 ◽  
Author(s):  
K. Akita ◽  
G. Zhang ◽  
S. Takahashi ◽  
H. Misawa ◽  
S. Tobe
Keyword(s):  
Thermal Spray ◽  
Bonding Strength ◽  
Thermal Spray Coatings ◽  
Fracture Mechanisms ◽  
In Situ Observation ◽  
Spray Coatings ◽  
Thermally Sprayed Coatings ◽  
Thermally Sprayed ◽  
Sprayed Coatings

Abstract Microscopic fracture mechanisms of thermal spray coatings under bending stress are investigated. Samples of thermally sprayed coatings were made using three distances. The sprayed powder was pure molybdenum. Vertical microcracks occur in lamellae and subsequently, these cracks join together and form vertical macrocracks in the samples sprayed with a short spraying distance. On the other hand, horizontal microcracks occur at the lamellae interfaces, and these cracks link together in the samples sprayed with a long spraying distance. These tendencies can be explained in terms of the hardness of the lamella and the bonding strength between each lamella. It is clarified that the bonding strength between each lamella corresponds to the applied strain at the point of rapid increase of the AE event count. The amplitude and rate of AE beyond the point of rapid increase are high in the coatings which formed macrocracks. It is concluded that the coating which has high resistance to crack formation has a high point of AE increase, low AE amplitude and low AE increasing rate.

Using In Situ Atomic Force Microscopy to Investigate the Kinetics of Corrosion of WC–Co–Cr Cermet Coatings Applied by High-Velocity Oxy-Fuel

2006 ◽  
Vol 129 (1) ◽  
pp. 55-68 ◽  
Author(s):  
V. A. D. Souza ◽  
A. Neville
Keyword(s):  
Atomic Force Microscopy ◽  
Thermal Spray ◽  
High Velocity ◽  
Thermal Spray Coatings ◽  
Aqueous Corrosion ◽  
Cermet Coatings ◽  
Force Microscopy ◽  
Spray Coatings ◽  
Atomic Force

Most of the early applications of thermal spray coatings were focused toward providing a remedy to excessive wear degradation. However, as the introduction of such coatings into wider industrial sections increases there is also exposure to other potential degradation processes—aqueous corrosion is one such process. The complex microstructures in cermet coatings have been shown to translate to complex modes of corrosion attack. In this paper an electrochemical test methodology to probe the local/microaspects of corrosion initiation and propagation will be described. A new electrochemical cell has been devised in which the corrosion can be followed “live” and in “real-time.” The surface is subjected to in situ imaging by atomic force microscopy which shows that not only the binder (Co, Cr) corrodes in high-velocity oxy-fuel thermal spray coatings but also the hard phase, with oxidation and dissolution of WC∕W2C taking place. Also potentiostatic tests indicated that the corrosion of WC-based coatings follows an Arrhenius relationship enabling the determination of activation energy (Ea) for the corrosion of WC and demonstrating that the oxidation and dissolution of WC are temperature, particle size, potential, and pH related

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