Surmet Engineering Better Material Solutions

Abstract: Performance of an Al–O–N based duplex coating system (DCS) was examined in order to improve the high-temperature oxidation resistance of superalloys and the low-pressure plasma sprayed NiCrAlY coatings. The DCS (;5 mm thick) was deposited using pulsed DC reactive magnetron sputtering as an external coating on Rene'N5 superalloy with and without NiCrAlY coating. DCS coatings were characterized using photo-stimulated luminescence spectroscopy, optical microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy before and after high-temperature oxidation.
© 2003 Elsevier B.V. All rights reserved.
Keywords: Oxidation; Thermally grown oxide; Coatings; Residual stress; Photostimulate luminescence

Abstract: Performance of an Al–O–N based duplex coating system (DCS) was examined in order to improve the high-temperature oxidation resistance of superalloys and the low-pressure plasma sprayed NiCrAlY coatings. The DCS (;5 mm thick) was deposited using pulsed DC reactive magnetron sputtering as an external coating on Rene'N5 superalloy with and without NiCrAlY coating. DCS coatings were characterized using photo-stimulated luminescence spectroscopy, optical microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy before and after high-temperature oxidation.
© 2003 Elsevier B.V. All rights reserved.
Keywords: Oxidation; Thermally grown oxide; Coatings; Residual stress; Photostimulate luminescence

Abstract: ALON® Optical Ceramic is a durable window material for UV, Visible and Mid IR window and dome applications. The mechanical, thermal, and optical properties of ALON products produced commercially by Surmet Corporation have been measured and this new data will be presented. Comparisons to previously measured data will be made. Optical quality, low scatter ALON having high strength that is nearly double previously reported has been made. Average strength values of 700 MPa at 21°C and 631 MPa at 500°C have been measured for ALON specimens prepared by precision surface finishing techniques. Polished optical domes tested have survived severe thermal shock tests. These strength levels are comparable to those for single crystal sapphire. Strength, thermal conductivity, thermal expansion, refractive index, emissivity and absorption coefficient will be presented. The possible mechanisms for the increased strength will be discussed.
Keywords: ALON, aluminum oxynitride, properties, strength, domes, transparent armor

Abstract: Durable coatings of silicon-carbon-oxy-nitride (a.k.a. SiCON) are being developed to protect high-speed missile windows from the environmental loads during flight. Originally developed at Rockwell Scientific Corporation (RSC) these coatings exhibited substantial promise, but were difficult to deposit. Under a DoD DARPA SBIR Phase I program, Surmet Corporation, working closely with RSC, is depositing these coatings using an innovative vacuum vapor deposition process. High rate of coating deposition and the ease of manipulating the process variables, make Surmet's process suitable for the deposition of substantially thick films (up to 30 μm) with precisely controlled chemistry. Initial work has shown encouraging results, and the refinement of the coating and coating process is still underway. Coupons of SiN and SiCON coatings with varying thickness on a variety of substrates such as Si-wafer, ZnS and ALON were fabricated and used for the study. This paper will present and discuss the results of SiN and SiCON coatings deposition and characterization (physical, mechanical and optical properties) as a basis for evaluating their suitability for high speed missile windows application. Keywords: Silicon-carbon-oxy-nitride (SiCON) Coatings, High speed missile windows, Plasma-enhanced CVD,

Abstract: Aluminum Oxynitride (ALON® Optical Ceramic) is a transparent ceramic material which combines transparency from the UV to the MWIR with excellent mechanical properties. ALON's optical and mechanical properties are isotropic by virtue of its cubic crystalline structure. Consequently, ALON is transparent in its polycrystalline form and can be made by conventional powder processing techniques. This combination of properties and manufacturability make ALON suitable for a range of applications from IR windows, domes and lenses to transparent armor. The technology for producing transparent ALON was developed at Raytheon and has been transferred to Surmet Corporation where it is currently in production. Surmet is currently selling ALON into a number of military (e.g., windows and domes) and commercial (e.g., supermarket scanner windows) applications.

hecapabilitytomanufacturelargeALONwindowsforbothsensorwindowandarmorapplicationsisinplace. ALON windows up to 20x30 inches have been fabricated. In addition, the capability to shape and polish these large and curved windows is being developed and demonstrated at Surmet. Complex shapes, both hyper-hemispherical and conformal, are also under development and will be described.
Key Words: Aluminum Oxynitride, ALON, MWIR windows, domes, ballistic armor

Abstract: New military requirements have reinvigorated the need for transparent magnesium aluminate (MgAl2O4) spinel. Surmet has developed a process that yields high quality transparent spinel at production scale. Several issues related to the extreme requirements of processing ultrafine spinel powders are described. Transmission data is presented for a significant dataset of parts made by this process.

More recently, the process has been expanded to include a capability for producing domes for the Joint Common Missile program. Domes at nominal 6” and 7” diameter have been successfully fabricated. Despite early challenges related to the forming portion of the process, a repeatable capability for these domes has been demonstrated.

Several challenges remain in spinel processing in order to support additional military requirements. In particular, the strength of the material needs further improvement. Also, improvements in optical quality with regard to inclusions are needed.

Keywords: spinel, MWIR windows, lenses, domes