Material Selection Session
 
16 August, Tuesday - Perak Room - 1:30pm - 3:15pm

Chair : Kukuh Soerowidjojo, Sandvik Materials Technology SEA​

Laboratory Testing of UNS N08028 and UNS N08029 for Downhole Application

16 August, Tuesday - Perak Room - 1:35pm - 2:05pm

Bio of Speaker

Abstract

Standard ISO 15156-3 (NACE standard MR0175) is essentially used for the material selection in H2S-containing environments when choosing cracking-resistant corrosion-resistant alloys (CRAs) in oil and gas production. Temperature and H2S partial pressure are considered as main parameters for materials selections. Laboratory testing is normally required for qualification of the materials by customer specifications. However earlier experiences indicated that UNS N08028 and UNS N08029 could withstand more severe environmental testing conditions compared to the standard required for type 4c alloys.
 
Recently a laboratory testing program has been carried out on the tube materials of UNS N08028 and UNS N08029 in 91000 mg/L chloride, 1000 psi CO2, 2200 psi H2S at temperature from 150 °C and up to 220 °C, by means of tensile constant load per NACE TM0177 and slow stain rate testing (SSRT) per NACE TM0198. Both UNS N08028 and UNS N08029 withstand the testing conditions. Pitting has been observed on these materials when chloride concentration was increased to 250000 mg/L after the constant load testing. Cracks have been observed in the SSRT when chloride was 254000 mg/L. The effects of chloride concentration and other possible parameters on the pitting and cracks have been discussed. UNS N08029 might have better crack resistance than UNS N08028 because its re-passivation property.

The Hydrogen Embrittlement of X80 Pipeline Steel under Cathodic Overprotection Environment

16 August, Tuesday - Perak Room - 2:10pm - 2:40pm

Bio of Speaker

Abstract

Name:   Lei Zhang
Title / Position:  Professor
Company:  University of Science and Technology Beijing(USTB)
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​Lei Zhang, Associate Professor of University of Science and Technology Beijing(USTB), Vice Director of Material Failure and Control Research Institution of New Material Technology Research Institute (USTB), Secretary of Environment Sensitive Fracture Committee of Chinese Society of Corrosion and Protection, Faculty Advisor of NACE China Student Section. His major researches focus on high temperature high pressure H2S-CO2 corrosion in oil & gas field, hydrogen embrittlement and stress corrosion cracking, stainless steel and anticorrosive alloy material selection, pipeline and structure failure analysis, pipeline corrosion integrity management, pipeline ICDA, etc.
The hydrogen damage behavior of X80 steel was investigated by hydrogen permeation, hydrogen content measurement, slow strain rate tension (SSRT), thermomechanical analysis and scanning electron microscope (SEM). The results indicated that the diffusible hydrogen concentration (c0) was proportional to the square root of applied cathodic current density (i), when i was less than a certain critical value, iH. However, once i was larger than iH, c0 has no correlation with i. The critical c0 for X80 hydrogen blistering was tested. SSRT results revealed that fracture morphology tended to be more brittle with the negative shift of applied potential.

ANALYSIS OF 25”CHOKE VALVE AFTER SERVICE

16 August, Tuesday - Perak Room - 2:45pm - 3:15pm

Bio of Speaker

Abstract

Name: Azzura Ismail
Title / Position:  Dr/Lecturer
Company:  Universiti Tun Hussein Onn Malaysia

​Dr. Azzura Ismail is a lecturer at Universiti Tun Hussein Onn Malaysia. She graduated from University Sains Malaysia and completed her Master’s Degree in materials engineering. Azzura then get her PhD from School of Mechanical Engineering, University of Leeds in corrosion engineering. While completing her PhD, she had collaborating experience with Aker Solution in Aberdeen, UK in corrosion related program especially in corrosion inhibitor. She has more than 13 years experience in teaching and currently serves at Universiti Teknologi Tun Hussein Onn Malaysia. Her research interest is in corrosion focusing in green corrosion inhibitor and material selection to retard corrosion. She is now a head of focus group for Nano Structure and Surface Modification research team of her faculty. In 2014, she received Malaysia Higher Education grant to work on research about green inhibitor. Until today she has published several papers and journal in corrosion issues and had supervised almost 100 students with the title ‘CORROSION’
An investigation has been performed on 25” Choke Valve after service in offshore to find the root cause of the valve failure. Carefully examination of the valve revealed very severe erosion corrosion on the inner circumference, fretting at seat and pitting corrosion at most of the parts.  Generally, most of the parts were made from various types of stainless steel and some was coated with carbide to increase the hardness. Closer examination of the valve using light and ultimately scanning electron microscopy showed there to be erosion-corrosion, pitting and crack was the causative mechanism of loss of mechanical strength. Some debris covered on valve has undergone for microscopy and elementary test to identify the corrosion product and to predict the mechanism that caused the failure. The result elucidate that the valve fails because of synergetic effect between corrosion and erosion-corrosion and some part  fails due to brittleness of carbide (coating). The analysis for corrosion product reveals that the debris found inside the valve was not corrosion product, but it is a constituent of sand sediment during operations of valve in downstream. The results from EDX shows that the highest content of chromium in stainless steel does not more than 18% which may categorized these stainless steel is not the higher grade of stainless steel and together with hardness results reveals that the valve was made from austenitic stainless steel. The thickness of the part was 1mm reduced due to erosion-corrosion. In conclusion, localized damage of 2.5” Choke Valve part most likely due to erosion-corrosion due to  pressure and velocity of the fluid flow and freeting corrosion was due to metal to metal contact in the valve.