Effect of Cr coating on creep behavior of zircaloy-4 alloy
(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Science and Technology on Reactor Fuel and Materials Laboratory, Nuclear Power Institute of China, Chengdu 610213, China;
3. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China)
2. Science and Technology on Reactor Fuel and Materials Laboratory, Nuclear Power Institute of China, Chengdu 610213, China;
3. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China)
Abstract: The effects of Cr coating, deposited by chemical vapor deposition, on the creep properties of Zr-4 alloy and the results for its stability during long-time service were reported. Its microstructure was studied by scanning electron microscopy, electron probe microanalysis, and electron backscatter diffraction. Results show that the grains of the Zr-4 matrix were equiaxed, exhibiting á0001？ texture parallel to the normal direction (á0001？//ND). Moreover, after the creep test, coated samples displayed a lower number of subgrain boundaries within their matrix compared with uncoated samples. Thus, the application of a Cr coating is instrumental in minimizing the stress on Zr-4, ultimately contributing to an enhancement in creep resistance of the coated samples. The Cr coating exhibits a high stability during long-term diffusion test. The coating cracks at a minimum stress of 157 MPa at 350 °C and 137 MPa at 400 °C. The Monkman-Grant relationship between the steady-state creep rate and creep fracture time was derived using a systematic summary of data pertaining to creep fracture.
Key words: Zr-4 alloy; Cr coating; creep behavior; microstructure; thermal stability