Inconel 713C is one of high strength Ni base heat resisting cast alloys.
The elevated temperature mechanical properties of this alloy are nearly equal to those of Nicrotung, Nimonic 115 and Udimet 700 but one of the weak points of this alloy is that it is sensitive to weld cracking.
In this study, the effect of carbon and aluminum+titanium content on weld cracking of this alloy was investigated in bead-on-plate test.
The effect of aluminum+titanium content on the elevated temperature (mechanical) properties was also inquired.
Furthermore, the influences of various heat treatments on the behavior of precipitated phases, micro-structures and hardness of Inconel 713C were investigated.
The results obtained in this study are summarized as follows:
(1) There are γ' phase [Ni3(Al, Ti)], Nb(C, N) and Cr23C6 in the precipitated phases of Inconel 713C.
γ' phase is almost dissolved into matrix after solution treatment at 1150°C for 5h and the hardness of this alloy falls from Hv 400-430 about Hv 330.
(2) The aging time to reach max. hardness of this alloy becomes shorter, as the aging temperature is higher.
Max. hardness is about Hv 450-470 under proper aging conditions.
The hardness does not drop so much after aging treatment at the temperature below 750°C for 500h.
This alloy is overaged after heat treatment at 800°C for 20h or at 900°C for 10h; its hardness is about Hv 350-360.
Hardness change is mainly affected by the particle size and distribution of γ' phase.
(3) The elevated temperature tensile properties of this alloy increases with increasing AI+Ti content as shown in Fig. 7 and 8.
Tensile strengthes at 700°C of 3.26(2.81Al, 0.45Ti), 4.85(3.58Al, 1.27Ti), 5.36(4.45Al, 0.91Ti) and 6.95(6.00Al, 0.95Ti) % Al+Ti alloy are respectively 39, 66, 72 and 74 kg/mm2 and at 800°C, are 37, 64, 69 and 78 kg/mm2.
(4) The reduction of area at 1100°C and 1200°C of this alloy decreases with increasing Al+Ti content.
(5) According to the result of bead-on-plate test, the effect of carbon content on weld cracking of this alloy is not clarified in the range of this study but the effect of Al+Ti content on that of this alloy is observed.
Dendrite boundary cracks, grain boundary cracks and recrystallized grain boundary cracks in H.A.Z. are found in 6.95% Al+Ti alloy but no cracks are detected in Inconel 713C of which Al+Ti content is less than 5.36%.
