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Surface Coating for Superplastic Forming Dies Disclosure Number: IPCOM000129004D
Publication Date: 2005-Sep-26
Document File: 1 page(s) / 27K

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Surface Coating for Superplastic Forming Dies

SPF of many parts is accomplished by blow-forming where a sheet blank is clamped in a steel die at elevated temperature (400C - 500C) and gas pressure is applied to one side.  It is critical in this process that the formed part release cleanly from the die.  Part sticking to the die can cause surface distortions and jeopardize the dimensional accuracy of the part.  This is especially true in the forming of class A outer body panels.  In most SPF applications, a parting agent such as graphite or boron nitride is included in the lubricating agent to help foster part release from the die.  However, these solid particles are expensive and pose several manufacturing issues.  Build-up of these particles on the die surface requires die cleaning which can be difficult at high temperature.  Additionally, these particles can embed themselves into the part and mar the part surface.  The application of a die coating that prevents part sticking can help reduce or possibly eliminate the need to use solid particles and has the potential to save significant cost.  

Another issue in SPF tooling is oxidation and in particular oxidation of the forming surface.  Oxidation of dies can damage the forming surfaces of SPF tools which in turn can lead to forming of parts with imperfections.  While cleaning dies after each run can remove some of the oxidation, the buildup is hard to control.  In some industries, dies made of ceramics or stainless steel are used to prevent oxidation.  While these approaches work, ceramic dies have very poor tool life and typically need to be replaced after just a few hundred formings.  Dies made of stainless steel are quite expensi...