Nadig, DS and Jacob, S and Karunanithi, R and Manjunatha, R and Subramanian, D and Prasad, MVN and Sen, Geetha and Jha, Abhay K (2010) Studies of cryotreatment on the performance of integral diaphragm pressure transducers for space application. In: 23rd Space Cryogenics Workshop (SCW), JUN 23-25, 2009, Arcadia, pp. 561-565.
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The integral diaphragm pressure transducers machined out of precipitation hardened martensite stainless steel (APX4) are widely used for propellant pressure measurements in space applications. These transducers are expected to exhibit dimensional stability and linearity for their entire useful life. These vital factors are very critical for the reliable performance and dependability of the pressure transducers. However, these transducers invariably develop internal stresses during various stages of machining. These stresses have an adverse effect on the performance of the transducers causing deviation from linearity. In order to eliminate these possibilities, it was planned to cryotreat the machined transducers to improve both the long-term linearity and dimensional stability. To study these effects, an experimental cryotreatment unit was designed and developed based on the concept of indirect cooling using the concept of cold nitrogen gas forced closed loop convection currents. The system has the capability of cryotreating large number of samples for varied rates of cooling, soaking and warm-up. After obtaining the initial levels of residual stress and retained austenite using X-ray diffraction techniques, the pressure transducers were cryotreated at 98 K for 36 h. Immediately after cryotreatment, the transducers were tempered at 510 degrees C for 3 h in vacuum furnace. Results after cryo treatment clearly indicated significant reduction in residual stress levels and conversion of retained austenite to martensite. These changes have brought in improvements in long term zero drift and dimensional stability. The cryotreated pressure transducers have been incorporated for actual space applications. (c) 2010 Published by Elsevier Ltd.
|Item Type:||Conference Paper|
|Additional Information:||Copyright of this article belongs to Elsevier Science.|
|Keywords:||Martensite; Residual stress; Retained austenite; Cryotreatment; Tempering.|
|Department/Centre:||Division of Physical & Mathematical Sciences > Centre for Cryogenic Technology|
|Date Deposited:||26 Oct 2010 07:29|
|Last Modified:||26 Oct 2010 07:29|
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