Sintered Reaction Bonded Silicon Parts by Microwave Nitridation Combined with Gas-Pressure Sintering

The cooperative project was a joint development program between Ceradyne and Oak Ridge National Laboratory through Lockheed Martin Energy Research (LMER). Cooperative work was of benefit to both parties. ORNL was able to assess the effect of the microwave nitridation process coupled with gas-pressure sintering for fabrication of parts for advanced diesel engines. Ceradyne gained access to gelcasting expertise and microwave facilities and experience for the nitridation of SRBSN materials. The broad objective of the CRADA between Ceradyne and OIWL was to (1) examine the applicability of the gelcasting technology to fabricate parts from SRBSN, and (2) to assess the effect of the microwave nitridation of silicon process coupled with gas-pressure sintering for fabrication of parts for advanced diesel engines. The following conclusions can be made from the work performed under the CRADA: (1) Gelcasting is a viable method to fabricate SRBSN parts using Ceradyne Si mixtures. However, the technique requires further development prior to being put into commercial use. (2) Microwave heating can be utilized to nitride multiple SRBSN parts. Scale-up of the process to fabricate several kilograms of material (up to 6 kg) per furnace run was demonstrated

Solid state sintering of silicon nitride ARL-CR-114. Final report

This report describes the development of Si{sub 3}N{sub 4}material compositions in the Si{sub 3}N{sub 4}-Y{sub 2}O{sub 3}-SiO{sub 2}-Mo{sub 2}C system with good high temperature stress rupture properties which could be used in engine components. Two distinct processing routes were examined in the course of the program: SSN and SRBSN. SRBSN was chosen for material property optimization. After characterization of two optimized compositions in the above system, demonstration engine components (exhaust valve blanks) were manufactured using the established processing procedures. Dimensional tolerance capabilities of the process were established and material properties of the components were shown to be comparable to those established during material development

Solid state sintering of silicon nitride ARL-CR-114. Final report

This report describes the development of Si{sub 3}N{sub 4}material compositions in the Si{sub 3}N{sub 4}-Y{sub 2}O{sub 3}-SiO{sub 2}-Mo{sub 2}C system with good high temperature stress rupture properties which could be used in engine components. Two distinct processing routes were examined in the course of the program: SSN and SRBSN. SRBSN was chosen for material property optimization. After characterization of two optimized compositions in the above system, demonstration engine components (exhaust valve blanks) were manufactured using the established processing procedures. Dimensional tolerance capabilities of the process were established and material properties of the components were shown to be comparable to those established during material development

Laser shock peening and mechanical shot peening processes applicable for the surface treatment of technical grade ceramics: a review

Laser shock peening and conventional mechanical shot peening are both comparable processes generally applicable to surface treat various metals and alloys. Commercial advantages offered by the laser systems such as flexibility, deep penetration of laser-induced shocks with precise control of the thermal pulses, shorter process times, high speeds, accuracy and aesthetics are attractive in comparison with the mechanical shot peening technique. Laser shock peening in the recent years has proved to be successful with steels, aluminium and titanium surfaces and metallic alloys in general. Nevertheless, minimal research has been conducted on laser shock peening and mechanical shot peening of technical grade ceramics. This article presents an update of the theory and to-date relevant literature within the two subject areas, as well as a comparison and a contrast between the mechanical and laser shock peening techniques. In addition, various gaps in knowledge are identified to propose further research for the development of both the techniques applicable to the surface treatment of technical grade ceramics