Time optimization of the step loading technique in hydrogen embrittlement small punch tests

• Published in: Theoretical and applied fracture mechanics 2022-02, Vol.117, p.103206, Article 103206
• Main Authors: Arroyo, B., Andrea, L., Gutiérrez-Solana, F., Álvarez, J.A.
• Format: Article
• Language: English
• Subjects: ASTM F1624; Cathodic polarization; Hydrogen embrittlement; Metal industry; Optimization; Small Punch test; Step loading technique; Test time optimization; Threshold stress
• ISSN: 0167-8442; 1872-7638
• DOI: 10.1016/j.tafmec.2021.103206

•Revision of ASTM F1624, based on the step loading technique, is carried out.•Review of the Small Punch Test (SPT) in aggressive environments is included.•An optimization step loading technique times when applied to SPT is carried out.•Minimum SPT times of 20 and 40 min for 1st-10th and 11th-20th steps was found.•Experimental correlation to estimate threshold stress based on SPT tests is proposed. The small punch tests consists of punching a plane small specimen until it breaks. This technique is very interesting in situations where there is a shortage of material. In recent works, it has been used with steel employed in aggressive environments, to estimate the threshold stress under which subcritical cracking will never occur. It has been presented in previous papers in combination with standard ASTM 1624, applying gradually increasing constant loads until the sample fails, to reduce the duration of the test and the results dispersión. In the present paper, a further optimization is performed on the steps durations for SPT, simplifying the test and therefore helping to reduce the lab workload while at the same time saving costs and resources and increasing productivity. The present work is carried out on an X80 medium-strength rolled steel in hydrogen embrittlement environments under three different levels of cathodic polarization in an acid electrolyte; the chosen steel belongs to the lowest hardness range (33 ≤ HRC