SBIR-STTR Award

This program proposes to develop advanced thermal barrier coatings and an advanced thermal insulating exhaust port runner to reduce high power density diesel engine heat rejection. Analytical Engineering, Inc. along with APS-Materials, Inc. and Ceradyne Thermal Materials will develop and bench test thermal barrier coatings that will address the important issues of thermal insulating effectiveness and durability. In addition, an advanced thermal insulation exhaust port ceramic monolith with compliant layer will be developed to accommodate the severe thermal shock and shrinkage that occurs during the casting process. Thermal barrier coatings will be developed to address the issues of radiation translucence and convective heat exchange between the coating surface porosity and in-cylinder gases. To maximize insulating effectiveness it is proposed that the thermal barrier coating combustion chamber surface porosity be closed off and sealed with materials that will either block or reflect thermal radiation. To maximize coating durability the plasma sprayed coating substrate will be engineered for optimum stress control by means of graded coatings, optimized grain size, controlled variable density distribution, micro-crack control, post-densification etc.

The U. S. Army has a need for reliable and durable in-cylinder thermal barrier coatings to reduce high power density diesel engine component structural temperatures and heat rejection. Phase I program bench testing results identified thermal barrier coating topcoat systems that reduced radiant heat transfer by 40 % and improved durability by more than 100 %. Two types of topcoat systems that were identified included a plasma sprayed system and a post-treatment slurry system. Bench test results demonstrated that radiant heat reflective coatings are desirable while radiant heat absorbing coatings are not desirable. It is proposed that further development of advanced top-coated thermal barrier coating systems will proceed by continuing to optimize the substrate plasma sprayed coating and topcoat processes while using bench test coupons that simulate the actual engine components to determine coating durability performance. Specially designed thermal bench test rigs will be constructed for testing thermal barrier coatings for the piston crown, cylinder head firedeck and the engine valve face. The bench test rigs will provide transient thermal loading to approach the engine component thermal loading conditions. Demonstration of thermal barrier coating durability and insulating performance will be performed on a high powered diesel engine.

Keywords:
Ceramic Coatings, Low Heat Rejection, High Power Density Engines