Showing papers by "Tarasankar Debroy published in 1984"

Alloying element vaporization and weld pool temperature during laser welding of AlSl 202 stainless steel

Abstract: Alloying element vaporization rates, plasma composition, and the changes in weld composition during laser welding of 202 stainless steel are discussed in this paper. Iron, manganese, and chromium were the most dominant species in the plasma. During laser welding it is always a difficult task to measure the temperature of the weld pool since this region is surrounded by hot plasma. In this paper a novel technique for the determination of weld pool temperature is presented. It is demonstrated that the relative rates of vaporization of any two elements from the molten pool can serve as an indicator of weld pool temperature, irrespective of the element pair selected. The composition of the solidified region calculated from the measured values of vaporization rate, plasma composition, and the volume of the solidified region was in good agreement with the weld composition determined by electron probe microanalyis technique.

The effects of CO and CO2 on the rate of Na2CO3 catalyzed boudouard reaction

Abstract: Discs of two cokes of different reactivity were gasified at 900 C in CO-CO/sub 2/-Ar mixtures. For both cokes the reaction rate increased with increasing Na/sub 2/CO/sub 3/ content. The lower the partial pressure of CO/sub 2/ and the higher the partial pressure of CO, the smaller was the influence of Na/sub 2/CO/sub 3/ addition. It was concluded that the rate of the catalysed reaction was controlled by more than one of the steps in any mechanistic schemes and that one of the slower steps was the regeneration of the carbonate.