An investigation into the use of a simple model for thickness uniformity on horizontal surfaces to describe thickness variations on vertical substrates

2007

Surface Engineering

The present paper presents finite element models to describe machine dynamics, such as electron beam (EB) generation in an EB gun, EB scanning on the surface of an ingot, melting process of the ingot, and vaporisation and deposition on the surface of a substrate during EB-PVD process. Based on physical models, the finite element models relate the input power to the EB gun and the temperature profile of the ingot surface, the temperature profile to the shape of vapour plume, and the vapour distribution to the coating thickness. The two deposition process models have been investigated for predicting the coating thickness and compared to experiments performed for simple shaped substrates. With preliminary studies, it is found that the presented models are suitable for a cost efficient computation and can aid in assessing process parameters.

Section: Ingot Heating/melting Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Finite element model for unified EB–PVD machine dynamics

Baek

2007

Surface Engineering

“…Real-time process control and monitoring of vapor plume composition (Anklam et al, 1995;Berzins et al, 1995) and melt pool condition (Lewis et al, 2000) for EB-PVD applications have also been studied. The cosine law of emission and related models has been used to predict the deposition thickness of simple planar substrates (Glang, 1976;Graper, 1973;Hill, 1986;Fancey and Matthews, 1993;James et al, 1995). Recently, a computational model for controlling thickness for workpieces with complex geometry such as turbine blades using finite-element techniques and a ray tracing algorithm has been developed (Cho et al, 2005).…”

Section: Multilayered Rhenium Coatingmentioning

confidence: 99%

Rapid manufacturing of rhenium components using EB‐PVD

Rapid Prototyping Journal

Fuke

Cho

et al. 2005

Rapid manufacturing of rhenium components using EB-PVD Vittal V. Prabhu Indraneel V. Fuke Sohyung Cho Jogender Singh Article information:To cite this document: Vittal V.If you would like to write for this, or any other Emerald publication, then please use our Emerald for Authors service information about how to choose which publication to write for and submission guidelines are available for all. Please visit www.emeraldinsight.com/authors for more information. About Emerald www.emeraldinsight.comEmerald is a global publisher linking research and practice to the benefit of society. The company manages a portfolio of more than 290 journals and over 2,350 books and book series volumes, as well as providing an extensive range of online products and additional customer resources and services.Emerald is both COUNTER 4 and TRANSFER compliant. The organization is a partner of the Committee on Publication Ethics (COPE) and also works with Portico and the LOCKSS initiative for digital archive preservation. AbstractPurpose -The purpose of this paper is to provide insights for understanding the relationship between rapid manufacturing process for rhenium components in jet nozzle fabrication using electron beam-physical vapor deposition (EB-PVD). Specifically, to develop a methodology to characterize and improve this new process through motion planning for maintaining uniformity in the deposition thickness. Design/methodology/approach -This research first identifies several important objectives for the process, and then develops an optimized heuristic method based on a look-ahead approach to generate motion plans for uniform thickness objective. In this heuristic, the surface of the workpiece is modeled using finite element method and the accumulated thickness of each layer on each element is computed based on its location in the vapor plume using a ray casting algorithm. Findings -Computational experiments show that the proposed algorithm can potentially provide significant improvements in the uniformity of the layers and cost savings in manufacturing compared to prevailing practice, especially for low-volume production such as aerospace applications.Research limitations/implications -In this research, net-shaped jet nozzle has been fabricated using a graphite mandrel. Therefore, the mandrelbased approach can be limited to producing hollow components. Practical implications -The proposed method is very generic and thus can be applied for multi-material manufacturing process identifying the sweet spot of the intersecting vapor plumes. Originality/value -This research can help the EB-PVD process for rapid manufacturing which has been considered as financially expensive to be accepted in real practice by providing a relationship of the process-to-product transformation through the developed motion planning methods.

“…5 The cosine model and its variants have been used in several evaporation applications to model the coating thickness of simple planar substrates. [14][15][16] However, there appears to be no published work on modelling coating thickness for workpieces with complex geometry such as turbine blades.…”

Section: Coating Model For Complex Geometriesmentioning

confidence: 99%

Intelligent automation of electron beam physical vapour deposition

Cho

Lewis²,

et al. 2005

Surface Engineering

The present paper presents an intelligent automation of the electron beam physical vapour deposition (EBPVD) process to achieve high quality and cost efficient coatings for low volume part production, using realtime feedback control. A computational model of EBPVD for predicting coating thickness is used with an optimisation heuristic for reducing coating thickness variance and feedback control approaches for substrate temperature control and melt pool control. The computational model can be readily generated using a standard computer aided design (CAD) model of the workpiece, which makes the method applicable to workpieces with complex threedimensional geometry. Based on this model, an optimisation heuristic for the EBPVD process is developed to control workpiece motion systematically with the objective of reducing coating thickness variance, i.e. providing a uniform coating. These computational developments are illustrated using a simulation of a turbine blade coating in which the coating thickness variance is reduced significantly. Process level intelligence is incorporated using realtime feedback control for substrate temperature and melt pool control using an open architecture control system. Results using thermocouple based temperature control and realtime vision for melt pool control are presented. Video images of the melt pool are analysed on a block by block basis, using a technique to identify critical regions of the melt pool. Simulation results demonstrate the feasibility of automating the electron gun beam steering sequence. The proposed methods offer the prospect of eliminating dedicated tooling/fixtures and improving the cost effectiveness of the process, especially for low volume production.