Thermal shock effects on type 316L austenitic steel and vanadium base alloys

Under abnormal conditions magnetically confined plasma can disrupt and hit the first wall. The unshielded structural alloy of the wall will then partially melt, evaporate and show crack initiation and propagation by the imposed high thermal stresses. Depending on the frequency and location of occurrence, the life-time of the first wall will be affected. The present work gives the results of thermal shock effects on the surface of plate from the 316L European reference heat and V-1Cr-0.1Ti alloy. Thermal shocks were generated by a laser beam with energy pulses of 20 J. Pulse length, frequency and number were varied with energy densities in the range of 2 MJ.m-2 to 10 MJ.m-2 per pulse, which is the range expected for plasma disruptions. With increasing number of pulses both steel and V increasingly evaporate. Short pulse durations promote evaporation. In and underneath melt layers intergranular cracks develop. Additionally fatigue specimens of Type 316 were exposed to laser pulses, simulating plasma disruption. Subsequently, fatigue tests have been performed. Strain ranges and frequencies are varied and the effects on cyclic life are discussed. (author)