INSTRUMENTACIÓN DE UN PÉNDULO PARA OBSERVAR LOS CAMBIOS DE TENACIDAD DE: UN ACERO 4140 TEMPLADO Y REVENIDO, FRAGILIZACIÓN POR HIDRÓGENO EN UN ACERO 1018 Y FRAGILIZACIÓN POR RADIACIÓN EN UN ACERO INOXIDABLE 316.

Abstract

In the present research is a pendulum instrument to observe changes in the tenacity of three physical phenomena that cause fragility in metallic materials. The first case study was to observe the changes of toughness: a quenched and tempered 4140 steel. Embrittlement phenomenon known as tempering. In the second case is weakened by introducing hydrogen in cathode loaded Charpy specimens in a 1018 steel, in order to observe the mechanical behavior in an instrumented impact test the phenomenon of hydrogen embrittlement. In the third case uses a nickel ion implanter to simulate neutron damage in a 316 stainless steel with similar characteristics to that of a nuclear reactor vessel. Damage known as radiation embrittlement. To study the first case was performed a microstructural analysis by SEM to observe the relationship with the fracture toughness in 4140 steel. The fracture toughness was quantified using an instrumented impact test with Charpy type specimens. 4140 steel was selected because this of embrittlement of steels that are part of the structural components of a reactor has an engineering challenge, since you need to use weaken reactors often control samples and samples radioactivity. An alternative is to use a particle accelerator to implant ions, these ions are implanted into the surface and depending on their atomic weight and density of the target (material to be studied) the degree of penetration damage or damaged area. One way to see how and when a crack nucleates and propagates can be carried out through tests on specimens notched Charpy type, tests were conducted at three points bending constant strain rate and instrumented Charpy pendulum, complementing observations of scanning electron microscopy of the damaged region containing the crack, trying to explain the degree of embrittlement and crack growth within the area affected by radiation (notch area).is a steel that is frequently used for the manufacture of machine parts susceptible to hardening in addition to annealing at different temperatures are achieved varying degrees of tenacity. The study was carried out in temperate Charpy type specimens in oil from 850 ° C and tempered at 100 ° C for 1hr, 1.5 hrs and 2hrs, in order to observe the elimination of hardening efforts. In addition, use a temperature of 400 ° C for 1hr, 1.5 hrs and 2hrs area where this steel temper embrittlement present. We found an increase in toughness with tempering time at 100 ° C while the hardness remained constant, but different behavior can be observed at 400 ° C with annealing time while the hardness decreases abruptly rises and falls tenacity. For the second case is weakened by introducing hydrogen in cathode loaded Charpy specimens of steel 1018, to observe the mechanical behavior in an instrumented impact test and observe the change in fracture toughness by the effect of hydrogen. In addition, a stress test shows a Embrittlement in the curves decrease in the percentage of deformation and found in the change of fracture mechanism on the surface of the specimens of coalecencia of pores cusiclivaje widespread. In contrast to the Charpy impact test how the curve changes slightly and the features of initiation shows more drastic changes and fractography area as the crack initiation and propagation show features of embrittlement in the specimens charged with hydrogen . In the third case it is known that radiation damage causes loss of ductility in structural steels, the assess the degree