Journal of Engineering Research Issue (5) March 2006 48 ON THE STABILIZATION OF RETAINED AUSTENITE F.B. Abudaia Department of Materials and Metallurgical Engineering, Al-Fateh University B.O. Box 13430, Tripoli, Libya E-mail: fabudaia@yahoo.com ﺍﻝﻤﻠﺨﺹ ﻋﺎﺩﺓ ﻤﺎ ﺘﺤﺘﻭﻯ ﺍﻝﻁﺒﻘﺎﺕ ﺍﻝﻤﺼﻠﺩﺓ ﻓﻲ ﺍﻝﺼﻠﺏ ﻋﻠﻰ ﻨﺴﺏ ﺼﻐﻴﺭﺓ ﻤﻥ ﻁـﻭﺭ ﺍﻻﻭﺴـﺘﻨﻴﺕ ﺍﻝﻤﺘﺒﻘـﻲ) ﻏﻴـﺭ ﺍﻝﻤﺘﺤﻭل.( ﺇﺤﺩﻯ ﺍﻝﻁﺭﻕ ﺍﻝﻤﺘﺒﻌﺔ ﻝﺘﺨﻔﻴﺽ ﻤﺤﺘﻭﻯ ﻁﻭﺭ ﺍﻻﻭﺴﺘﻨﻴﺕ ﻓﻲ ﻤﺜل ﻫﺫﻩ ﺍﻝﺤﺎﻻﺕ ﻫﻭ ﺍﺴـﺘﺨﺩﺍﻡ ﺍﻝﺘﺒﺭﻴـﺩ ﺍﻝﻌﻤﻴﻕ ﻋﻥ ﻁﺭﻴﻕ ﺍﻝﻐﻤﺭ ﻓﻲ ﺍﻝﻨﻴﺘﺭﻭﺠﻴﻥ ﺍﻝﺴﺎﺌل. ﺴﻴﺘﻡ ﻓﻰ ﻫﺫﺍ ﺍﻝﺒﺤﺙ ﺘﻘﻴﻴﻡ ﺯﻴﺎﺩ ﺓ ﺜﺒﺎﺕ ﻁﻭﺭ ﺍﻻﻭﺴﺘﻨﻴﺕ ﻤﻊ ﺍﻝﺘﻘﺎﺩﻡ ﺒﻤﺩﻯ ﺼﻌﻭﺒﺔ ﺘﺤﻭل ﻁﻭﺭ ﺍﻻﻭﺴﺘﻨﻴﺕ ﺍﻝﻤﺘﺒﻘﻲ ﺇﻝﻰ ﻁﻭﺭ ﺍﻝﻤﺎﺭﺘﻨﺴﻴ ﺕ ﺒﺎﺴﺘﺨﺩﺍﻡ ﻋﻤﻠﻴﺎﺕ ﺍﻝﻐﻤﺭ ﺒﻌﺩ ﻭﻗﺒل ﺍﻝﺘﻌﺘﻴﻕ. ﻓﻲ ﻫﺫﺍ ﺍﻝﺒﺤﺙ ﺘﻤﺕ ﺩﺭﺍﺴﺔ ﺘﺄﺜﻴﺭ ﺍﻝﺘﻘﺎﺩﻡ ﻋﻠﻰ ﺜﺒﺎﺕ ﻁﻭﺭ ﺍﻻﻭﺴﺘﻨﻴﺕ ﻤـﻊ ﺍﺴـﺘﺒﻌﺎﺩ ﺘـﺄﺜﻴﺭ ﺍﻹﺠﻬـﺎﺩﺍﺕ ﺍﻝﻤﺘﺨﻠﻔﺔ ﺍﻝﻨﺎﺘﺠﺔ ﻤﻥ ﺠﺴﻡ ﺍﻝﻤﺸﻐﻭﻻﺕ ﺍﻝﻤﻜﺭﺒ ﻨﻪ ﻭﺫﻝﻙ ﺒﺎﺴﺘﺨﺩﺍﻡ ﻋﻴﻨﺎﺕ ﻤﻥ ﺍﻝﺼﻠﺏ ﺍﻝﻜﺭﺒﻭﻨﻲ ﺒﺴﻤﻙ1 ﻤﻡ ﻝﻤﺤﺎﻜﺎﺓ ﺍﻝﻁﺒﻘﺔ ﺍﻝﻤﺼﻠﺩﺓ ﻓﻲ ﻋﻤﻠﻴﺎﺕ ﺍﻝﻜﺭﺒﻨﻪ. ﺘﻡ ﺍﺴﺘﺨﺩﺍﻡ ﺤﻴﻭﺩ ﺍﻷﺸﻌﺔ ﺍﻝﺴﻴﻨﻴﺔ ﻝﺤﺴﺎﺏ ﻨﺴﺏ ﻁﻭﺭ ﺍﻻﻭﺴـﺘﻨﻴﺕ ﺍﻝﻤﺘﺒﻘـﻲ ﻭﻝﻠﻜﺸﻑ ﻋﻥ ﺍﻝﺘﻐﻴﺭ ﻓﻲ ﺍﻝﻤﺤﺘﻭﻯ ﺍﻝﻜﺭﺒﻭﻨﻲ ﻓﻲ ﻁﻭﺭﻱ ﺍﻻﻭﺴﺘﻨﺎﻴ ﺕ ﻭ ﺍﻝﻤﺎﺭﺘﻨﺴﻴﺕ ﻭﺤﺴﺎﺏ ﺍﻹﺠﻬـﺎﺩﺍﺕ ﺍﻝﺩﺍﺨﻠﻴـﺔ ﺍﻝﻨﺎﺘﺠ ﺔ ﻋﻥ ﺘﺤﻭل ﻁﻭﺭ ﺍﻻﻭﺴﺘﻨﺎﻴ ﺕ ﺇﻝﻰ ﺍﻝﻤﺎﺭﺘﻨﺴﻴﺕ ﺒﺎﻝﻁﺒﻘﺔ ﺍﻝﻤﺼﻠﺩﺓ. ﺒﻤﻘﺎﺭﻨﺔ ﺍﻝﻨﺘﺎﺌﺞ) ﻤﺨﻁﻁﺎﺕ ﺤﻴﻭﺩ ﺍﻷﺸﻌﺔ ﺍﻝﺴﻴﻨﻴﺔ( ﻝﻌﺩﺓ ﻋﻴﻨﺎﺕ ﺘﻡ ﺇﺨﻀﺎﻋﻬﺎ ﻝﻌﻤﻠﻴﺎﺕ ﺘﻌﺘﻴﻕ ﻭﻏﻤﺭ ﻤﻊ ﺃﺨـﺭﻯ ﻏﻴﺭ ﻤﻌﺘﻘﺔ ﻭﺠﺩ ﺇﻥ ﻋﻤﻠﻴﺎﺕ ﺍﻝﺘﻌﺘﻴﻕ ﺘﺅﺩﻱ ﺇﻝﻰ ﺯﻴﺎﺩﺓ ﺜﺒﺎﺕ ﻁﻭﺭ ﺍﻻﻭﺴﺘﻨﺎﻴ ﺕ ﻨﺸﺅ ﺍﺠﻬﺎﺩﺍﺕ ﻀﻐﻁ ﻤﻊ ﺍﻝﺘﻘﺎﺩﻡ ﻭﺃﻥ ﻤﺘﺨﻠ ﻔﺔ ﺼﻐﻴﺭﺓ ﺒﺩﺍﺨل ﺍﻝﻁﺒﻘﺔ ﺍﻝﻤﺼﻠﺩﺓ ﻨﺘﻴﺠﺔ ﺘﺤﻭل ﻁﻭﺭ ﺍﻻﻭﺴﺘﻨﺎﻴ ﺕ ﺇﻝﻰ ﺍﻝﻤﺎﺭﺘﻨﺴﻴﺕ ﻗﺩ ﻴﺅﺩﻱ ﺇﻝﻰ ﻤﻨـﻊ ﺘﺤـﻭل ﺇﻀﺎﻓﻲ ﻤﻥ ﻁﻭﺭ ﺍﻻﻭﺴﺘﻨﺎﻴﺕ ﺇﻝﻰ ﺍﻝﻤﺎﺭﺘﻨﺴﻴﺕ. ﻝﻭﺤﻅ ﻋﺩﻡ ﺘﻐﻴﺭ ﻓﻲ ﺍﻝﻤﺤﺘﻭﻯ ﺍﻝﻜﺭﺒﻭﻨﻲ ﻝﻁﻭﺭ ﺍﻻﻭﺴﺘﻨﺎﻴﺕ ﺒـﺴﺒﺏ ﺍﻝﻤﺤﺘﻭﻯ ﺍﻝﻤﺭﺘﻔﻊ ﻝﻌﻨﺼﺭ ﺍﻝﻜﺭﺒﻭﻥ ﺒﻁﻭﺭ ﺍﻻﻭﺴﺘﻨﺎﻴ ﻋﻤﻠﻴﺎﺕ ﺍﻝﺘﻌﺘﻴﻕ ﻭﺃﻥ ﺕ ﺍﻝ ﻤﺘﺒﻘﻲ ﻴﺼﺎﺤﺏ ﻫﺫﺍ ﺍﻝﻁﻭﺭ ﻗﺒل ﻋﻤﻠﻴﺔ ﺍﻝﺘﻌﺘﻴﻕ. ﻴﺭﺠﺢ ﺃﻥ ﻴﻜﻭﻥ ﺍﻝﺴﺒﺏ ﺍﻝﺭﺌﻴﺴﻲ ﻝﺯﻴﺎﺩﺓ ﺜﺒﺎﺕ ﻁﻭﺭ ﺍﻻﻭﺴﺘﻨﺎﻴ ﺕ ﺍﻝﻤﺘﺒﻘﻲ ﺃﺜﻨﺎﺀ ﺍﻝﺘﻌﺘﻴﻕ ﻫﻭ ﺇﻋﺎﺩﺓ ﺘﻭﺯﻉ ﺍﻝﻜﺭﺒﻭﻥ ﻋﻥ ﻁﺭﻴﻕ ﻨﺯﻭﺡ ﺍﻝﻜﺭﺒﻭﻥ ﻤﻥ ﻁﻭﺭ ﺍﻝﻤﺎﺭﺘﻨﺴﻴﺕ ﺃﺜﻨﺎﺀ ﺍﻝﺘﻌﺘﻴﻕ ﻜﻤﺎ ﻫﻭ ﻭﺍﻀﺢ ﻤﻥ ﺍﺨﺘﻔﺎﺀ ﺍﻻﺯﺩﻭﺠﺎﺕ ﻓﻲ ﻗﻴﻡ ﻁﻭﺭ ﺍﻝﻤﺎﺭﺘﻨﺴﻴﺕ ﻓﻲ ﻤﺨﻁﻁﺎﺕ ﺤﻴﻭﺩ ﺍﻷﺸﻌﺔ ﻭﺍﻨﺘﺸﺎﺭﻩ ﺇﻝﻰ ﺍﻝﺨﻼﻋﺎﺕ ﻓﻲ ﺍﻝﺤﺩﻭﺩ ﺍﻝﻔﺎﺼﻠﺔ ﺒﻴﻥ ﻁﻭﺭﻱ ﺍﻻﻭﺴـﺘﻨﺎﻴ ﺕ ﻭ ﺍﻝﻤﺎﺭﺘﻨﺴﻴﺕ ﻤﻤﺎ ﻴﺅﺩﻱ ﺇﻝﻰ ﺇﻋﺎﻗﺔ ﺤﺭﻜﺔ ﺍﻝﺤﺩﻭﺩ ﺍﻝﻔﺎﺼﻠﺔ ﻭﺒﺎﻝﺘﺎﻝﻲ ﺯﻴﺎﺩﺓ ﺼﻌﻭﺒﺔ ﺘﺤﻭل ﻁﻭﺭ ﺍﻻﻭﺴﺘﻨﻴﺕ ﺍﻝﻤﺘﺒﻘـﻲ ﺇﻝﻰ ﻁﻭﺭ ﺍﻝﻤﺎﺭﺘﻨﺴﻴﺕ ﺃﺜﻨﺎﺀ ﻋﻤﻠﻴﺎﺕ ﺍﻝﺘﺒﺭﻴﺩ ﺍﻝﻼﺤﻕ ﺒﺎﻝﻐﻤﺭ. ABSTRACT Carburized layers in quenched steel components usually contain few percent of retained austenite (RA). Deep freezing treatment by dipping in liquid nitrogen is usually carried out when it is required to reduce the amount of retained austenite to very low levels. Stability of retained austenite due to aging was assessed by the difficulty of transformation of retained austenite to martensite when subjected to sub-zero treatment. In this work the case material was simulated by carburizing thin specimens of 1mm thick to obtain full through hardening by carburization. Retained austenite was found to