Sponsoring Company: Pratt & Whitney—United Technologies Corp.

Project Title: Improved Sample Holder for Thermal Gradient Testing

Contacts:

Elisa Zaleski, PhD

(860) 557-4232

The Engineering Challenge:

The ability to test current and future high temperature materials, particularly coatings, in an engine relevant, lab-scale environment is critical to the prediction of coating performance and lifing. Degradation by molten siliceous debris is of particular concern, as this degradation mode is especially susceptible to the presence of a thermal gradient.

At UConn, Professor Eric Jordan with the support of Pratt & Whitney, has developed Thermal Gradient Rigs (TGR-1 and TGR-2) that subject coated circular disk specimens to cyclic thermal loading (see figure 1). While these test rigs have produced critical data used in the evaluation of high temperature coatings, the current sample holder design suffers from high cost consumable alumina bolts, severe thermal gradients induced at the bolt heads leading to edge-induced failure, and limitations on the durability of the holder due to the severe environment generated by the flame (see figure 2). An improved sample holder design would reduce or eliminate these critical limitations.

Description of Problem/Project:

The objective of this project is to research, design and fabricate a sample holder for the UConn TGR, with a particular emphasis on TGR-2. The holder must be capable of exposing the sample to the thermal and siliceous environment while eliminating the alumina bolts and minimizing edge stresses and artificial hot spots. The holder should allow for sufficient backside cooling, line of sight access for non-contact temperature measurement, and be compatible with the thermochemical environment (i.e. CMAS). Ideally, temperature measurement via thermocouples would also be possible. Modification of the sample geometry could be incorporated if necessary, with due consideration for the economics of such a change.

Expected Deliverables:

  • Research and benchmarking of potential sample holder designs for other thermal gradient rigs (both flame and laser-based)
  • Analysis of thermal environment of the sample and sample holder and the heat transfer between the two to determine any potential radial thermal gradients or hot spots
  • Selection of a preferred design based on the above analysis
  • Design and fabrication of a prototype holder
  • Design or note the modifications required to use the new holder in both TGR-1 and TGR 2
  • Feasibility test of holder, noting failure location of samples, radial gradients, hot spots, and effect of CMAS (can be done on either TGR-1 or TGR-2 pending the testing requirements of P&W)

Figure 1 Circular disk specimen with high velocity plasma torch

Figure 2.(a) Hot spots arising at the alumina bolts and (b) the concomitant damage arising at the hot edge in the current sample holder configuration.

  • Is there a specific software package required for the projects? Y __ N _X_

Which package (name/version) ______

  • U.S. Citizen/Person (green card) Required? Y_X_ N __
  • Will Export Controlled data be used in project (EAR/ITAR) Y _X_ N__
  • NDA/IP Agreements required? Y _X_ N __
  • Other considerations: Previous Senior Design Teams have worked other aspects of the CMAS problem. Their reports and data can be used to aide in the design of this new sample holder.