| Budget Amount *help |
¥8,300,000 (Direct Cost: ¥8,300,000)
Fiscal Year 1987: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1986: ¥7,400,000 (Direct Cost: ¥7,400,000)
|
|---|
| Research Abstract |
Repid solidification of alloys is expected to improve their mechanical properties. Because at least one dimension of the material should be small in order to rapidly extract heat from the melt, materials produced so far by rapid solidification processing are in the forms of flakes, rebons, wires or powders which require further processing to obtain useful bulk materials. On the other hand, thermal-spraying combines rapid solidification and consolidation in a single operation and relatively thick deposite can be produced. In the present work, four Fe-C-Cr-Si alloy powders containing 3.5wt%C, 10-40wt%Cr and 0.8-1.5wt%Si were thermal-sprayed.
In the low-pressure plasma deposition process, all the as-sprayed deposites contains metastable ausenite. At the present time, However, it is found difficult to cool the deposite sufficiently in the low pressure chamber, and so, the major part of the present work were carried out using a flame-spray-gun with special attachment to densify and cool the deposite. The deposted layer has a thickness of about 500um. The cooling retes achieved are 10^5-10^6k/s. Metastable austenite supersaturated with C and Cr exists in all the as-sprayed deposites, and the deposites with high Cr content contains ferrite, too. At the annealing temperature of 873K, the austenite disappears and equilibrium ferite and carbides, which are M_3C, M_7C_3 or M_<23>C_6 depending on the alloy composition,form. The microhardness of the as-sprayed deposit is very high. On annealing at 473 or 673K, the microhardness reaches a maximum due to the precipitation of fine carbide. The pore and the oxide in the deposit make the tensile strength and Young's modulus of the deposit lower compared with the fully dense materials.
|
