PRECIPITATION HARDENING IN NICKEL-BASED SUPERALLOYS - EFFECT OF ALLOYING

The growth kinetics of gamma' precipitates in Ni based wrought superal loys was investigated, using a computer aided X-ray. analysis method. It was found that the growth process obeys the Lifshitz-Slyozov-Wagner law. Regression formulae describing the liquidus, solidus, and gamma' soltus temperatures as functions of the overall composition were esta blished. The heat treatment window as a function of composition and it s effect on homogenisation and retained hardness were determined. The high retained hardness of homogenised Al + Ti rich alloys hinders thei r commercial use as Ni base wrought superalloys.