The problem of hydrogen embrittlement in ultra-high-strength steels is well known. In this study, slow strain rate, four-point bending, and permeation tests were performed with the aim of characterizing innovative materials with an ultimate tensile strength higher than 1000 MPa. Hydrogen uptake, in the case of automotive components, can take place in many phases of the manufacturing process: during hot stamping, due to the presence of moisture in the furnace atmosphere, high-temperature dissociation giving rise to atomic hydrogen, or also during electrochemical treatments such as cataphoresis. Moreover, possible corrosive phenomena could be a source of hydrogen during an automobile’s life. This series of tests was performed here in order to characterize two press-hardened steels (PHS)—USIBOR 1500® and USIBOR 2000®—to establish a correlation between ultimate mechanical properties and critical hydrogen concentration.

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A 16Cr5NiMo supermartensitic stainless steel was subjected to different tempering treatments and analyzed by means of permeation tests and slow strain rate tests to investigate the effect of different amounts of retained austenite on its hydrogen embrittlement susceptibility. The 16Cr5NiMo steel class is characterized by a very low carbon content. It is the new variant of 13Cr4Ni. These steels are used in many applications, for example, compressors for sour environments, offshore piping, naval propellers, aircraft components and subsea applications. The typical microstructure is a soft-tempered martensite very close to a body-centered cubic, with a retained austenite fraction and limited δ ferrite phase. Supermartensitic stainless steels have high mechanical properties, together with good weldability and corrosion resistance. The amount of retained austenite is useful to increase low temperature toughness and stress corrosion cracking resistance. Experimental techniques allowed us to evaluate diffusion coefficients and the mechanical behaviour of metals in stress corrosion cracking (SCC) conditions.

Nowadays Al-Si coated boron steels (that are Advanced High Strength Steels, AHSS) are largely used in vehicle bodies. If on one hand they offer great mechanical performances, on the other hand they are susceptible to hydrogen delayed fracture. As this phenomenon brings to the reject of the component during production or even worse the failure during operation, diffusible hydrogen absorbed in the component needs to be monitored during plant process. A simple procedure, by means of a solid-state innovative sensor, is developed to check diffusible hydrogen concentration during laboratory experiments and manufacturing process. The behavior of an Al-Si coated boron steel after hydrogen absorption is investigated by means of slow strain rate mechanical tests (SSRT) and correlated to the diffusible hydrogen content. Finally, in manufacturing process an extensive plant test campaign is performed on semi-manufactured vehicle parts in order to verify the laboratory's results. These tests confirmed the possibility to approach the evaluation of diffusible hydrogen content in semi-products during car manufacturing by means of an easy procedure based on a robust sensor.

Corrosion is evaluated to be one of the most important cause for pipeline failures. Given the serious consequences of these events in terms of human safety, environmental preservation and cost saving, it is evident that on-field corrosion control could have a fundamental role. The aim of the present work was to meet this need with preliminary feasibility study to develop a test procedure, characterized at the same time by non-invasive approach and scientific rigor, to evaluate the possibility of on-line monitoring and assess the integrity of a pipeline during its operation. The experimental campaign was performed on a HSLA Steel X60, characterized by a ferritic microstructure with fine grains and ultimate tensile strength equal to 520MPa. The hydrogen interaction with steel was investigated by means of an advanced equipment based on an innovative high sensitivity hydrogen gas sensor. The following types of investigations were carried out [1]: - Various permeation tests were performed with reference to EN ISO 17081:2014 increasing test temperature from 10°C to 60°C. - Afterwards a series of Hydrogen Induced Cracking nucleation tests was performed with reference to ASTM STP 692:0. - Finally, permeation concept was applied in an innovative way to Hydrogen Induced Cracking nucleation phenomena.