Proton Irradiated Microstructural and Mechanical Properties ...

Proton Irradiated Microstructural and Mechanical Properties Investigation for Alloy 718 Mi Wang1, Miao Song1, Gary. S. Was1, Chinthaka Silva2, Lawrence Nelson3, Gabriel Ilevbare4 1

University of Michigan 2 Oak Ridge National Laboratory 3 JLN Consulting 4 Electric Power Research Institute

Project sponsored by EPRI (MA10001593) International Light Water Reactors Material Reliability Conference and Exhibition, Chicago, IL, USA, August 1 – 4, 2016.

Nickel-base alloy 718 • Structural application in Pressurized Water Reactors (PWRs) • Fuel assembly components • Hold down springs • Grid springs

• High strength alloy • Precipitates strengthening: 𝛾′ (Ni3(Ti, Al)), 𝛾″ (Ni3Nb) phases • Excellent mechanical properties • High resistance of corrosion (~18% wt. Cr) Specification

Thermal treatment

YS (MPa)

Tensile Strength (MPa)

Elongation (%)

AMS 5596, ASTM B 670, AMS 5662, 5663 ASTM B, SB 637

Anneal at 927-1010C; Age at 718C(8h); FC, Age at 621C (10h);

1034

1241, 1276

12

Modified grade 718

Anneal at 1093C; Age at 718C(4h); Age at 621 (16h)

874-884

1112-1126

43-43.4

2

Project alloy 718 • Objective: Fill in the technical gaps of alloy 718 in fuel assemblies and associated components. • Non-irradiated microstructure development based on various thermo-mechanical treatments (effect of cold work…) • Mechanical property variations depending on different thermo-mechanical treatments • Microstructure changes induced by proton irradiation (phase stablity, radiation hardening,...) • An understanding for the evolution of mictrosturcture with irradation and its effect on IASCC susceptibility

3

Alloy 718 • Two different heats Alloy

Ni

Fe

Cr

Nb

Mo

Ti

Al

C

Si

Ta

Cu

Co

Mn

P

S

N

52.77

18.95

18.46

5.2

2.9

0.96

0.61

0.036

0.02

0.01