How It’s Done:
Crystal Casting
The techniques used in the casting of single crystal investment parts are well-guarded secrets. We look behind the curtain of the secretive niche. SHEA GIBBS, MANAGING EDITOR
T
urbine blade producers leave nothing to chance. A tour of Alcoa How- met’s Whitehall, Mich.,
plant will leave the visitor wanting for a view of the pouring area. Another industry leader, Precision Castparts Corp., Portland, Ore., typically won’t let outsiders even that close—the company has repeatedly turned down requests for comments and tours. And a turbine parts OEM that recently expanded its in-house casting capabilities, Chro- malloy, Palm Beach Gardens, Fla., curtained off multiple areas of its plant during its grand opening ceremonies on Dec. 2, 2010. “We’re just a little careful, let’s say,”
said Andrew Farrant, Chromalloy’s vice president of marketing and corpo- rate communications.
32 | MODERN CASTING August 2011 Te three companies make parts
for aerospace and power generation turbines. Te castings used in the applications generally are produced in nickel-based superalloys and can take on one of three microstructural orientations—equiaxed, directionally solidified or single crystal. Single crystal castings are the
Cadillacs of the group. Because of their boundary free grain orienta- tion, the parts are stronger and more heat resistant than castings with more conventional microstructures. “Single crystal castings are uniquely difficult to manufacture,” said Paul Mikkola, PPM Consulting & Design LLC, Bedford, N.H., who spent a decade working in the investment casting industry before starting a consulting firm. “Te typical [metal-
caster] doesn’t have the knowledge of the solidification and grain growth. It is limited to a small niche that has a strong technical staff, and that has limited the process’ growth.” Te segment of metalcasters making
single crystal parts has reason to protect its intellectual property. Te high-perfor- mance parts the manufacturers produce go to customers that understand the value of paying for improved properties (commercial airlines, the U.S. Air Force, power generator manufacturers, the U.S. Navy and cruise lines), and to preserve those relationships, single crystal cast- ers are heavily invested in limiting the growth of competition.
Secrets Don’t Make Friends What is known is that blade
producers are focused on the “hot Single
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