table iv there is virtually no microsegregation or chemical inhomogeneity in the as plasma spray cast material relative to conventionally melted and cast material fig1 is a transmission electron micrograph at 20 000 u00d7 of a thin foil specimen which shows the microstructure of as plasma spray cast rene 39 80 as in fig1 following a 2 hour treatment at 2190 u00b0 f 1200 u00b0 c the grains have grown to an average size of about 5 microns yet remain small in comparison to that of conventionally melted and cast rene 39 80 gamma prime precipitates are visible in the interior of the grains heat treatment at lower temperatures e g the two hour heat treatments at 2100 u00b0 f 1150 u00b0 c referred to above in example i resulted in even less grain growth i e the grain size was on the order of from about 2 0 to about 3 0 microns and theoretically there is even less microsegregation due to the homogenization effects of the elevated temperature heat treatment the stability of rene 39 80 to grain growth at elevated temperatures was anticipated since this superalloy is strengthened by the precipitation of the gamma prime phase table iv______________________________________ conventionally melted and cast rene 39 80element ti al cr co______________________________________range 3 51 9 33 2 26 3 26 9 73 14 65 8 32 9 92 wt avg 5 1 2 7 12 37 9 13 wt range u00b1 80 u00b1 20 u00b1 20 u00b1 9aboutavg ______________________________________ plasma spray cast rene 39 80element ti al cr co______________________________________range.