#carburization

[uniabex]

Understanding Creep and Overheating Damage in Industrial Tubes

In high-temperature industrial environments, such as refineries, power plants, and petrochemical units, tubes face extreme thermal and mechanical stress. Over time, these conditions can cause creep—a slow, permanent deformation of metal under sustained heat and pressure. This damage typically manifests as swelling, bulging, or distortion in tube walls, which can compromise mechanical integrity and operational safety.

Creep occurs when the material’s microstructure gradually changes at elevated temperatures, reducing its load-bearing capacity. In severe cases, it can lead to catastrophic tube rupture, unplanned shutdowns, and costly repairs. Identifying creep damage early is crucial for extending equipment lifespan and ensuring plant safety.

Another common issue is overheating damage, where localized hot spots weaken tube metal, often visible through discoloration, oxidation, or surface roughness. These hot spots may arise from poor heat distribution, blocked fluid flow, or burner misalignment. Left unchecked, overheating accelerates creep and other forms of metallurgical degradation.

Preventive maintenance is the key to mitigating these risks. Regular inspection techniques such as ultrasonic thickness testing, metallographic analysis, and thermal imaging can detect early signs of creep and overheating. Additionally, upgrading to high-grade alloys with superior creep resistance can significantly improve tube performance in harsh operating environments.

At Uni Abex, we specialize in delivering high-performance centrifugal cast tubes and components engineered to withstand the toughest industrial conditions. Our metallurgical expertise ensures that your equipment remains reliable, efficient, and safe—minimizing downtime and maximizing ROI.

Early detection, timely intervention, and material excellence can make all the difference in preventing failures caused by creep and overheating. A proactive approach ensures operational continuity while safeguarding both personnel and assets.

[ijtsrd]

Utilization of Melon and Snail Shell Waste Mixtures in the Carburization of Mild Steel

by Adzor, S. Abella | Ihom, P. Aondona | Edibo, S." Utilization of Melon and Snail Shell Waste Mixtures in the Carburization of Mild Steel" 

Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-3 , April 2018, 

URL: http://www.ijtsrd.com/papers/ijtsrd11353.pdf  

Direct URL: http://www.ijtsrd.com/engineering/industrial-engineering/11353/ utilization-of-melon-and-snail-shell-waste-mixtures-in-the-carburization-of-mild-steel/adzor-s-abella

call for paper engineering, paper publication for engineering, engineering journal

As long as industrial and agricultural activities go on, wastes will continue to be generated. In view of this, wastes recycling/or conversion to other reusable materials that can be utilize by another industrial set-up is fast receiving worldwide attention. In this research work, the assessment of the suitability of melon and snail shell wastes mixtures in enhancing the surface hardness of mild steel via the pack carburization method has been investigated. The carburization process was carried out at the temperatures of 9000C, 9200C and 940oC for the soaking times of 15, 30, 45 and 60 minutes respectively, and then quenched in water to harden. Thereafter, they were tempered at 2500Cfor 1 hour to relieve the residual stresses introduced into the steel specimens as a result of quenching. Standard method was adopted to determine the surface hardness of the carburized and un-carburized test specimens. Micro-structure examination was also performed using standard metal lographic techniques to observe the micro structures formed. The results of the study showed increase in the surface hardness of all the carburized steel specimens in the different carburizing media. The steel specimens carburized with 80% snail shell wastes plus 20% melon shell wastes mixture had higher hardness values than those carburized with 100% snail shell wastes only. The maximum surface hardness values of 118VHN, 128VHN and 129VHN were obtained at the carburizing temperatures of 9000C, 9200C and 9400C respectively, for the soaking time of 60 minutes with the specimens carburized with snail and melon shell wastes mix. It was observed that the process variables (temperature and soaking time) significantly impacted on the quantity of carbon absorbed at the steel surface as depicted by the surface hardness values. The results of the research work have established the viability of melon and snail shell wastes mixture as an alternative source of carburizers in enhancing the surface hardness of mild steel. 

[heanjiaalloys]

Corrosion behaviour of Inconel 625 in different application conditions

Inconel 625 is immune to intergranular corrosion by precipitation of niobium carbides at 927oC to 1038oC annealing temperature. Niobium carbides interact with carbon to precipitate as chromium carbides in the grain boundaries. Chromium depletion near the grain boundaries is resulted by intergranular chromium carbide precipitation. It occurs at specific temperatures and is called as sensitization. Alloy’s sensitization makes it less sensitive to intergranular corrosion. Inconel 625 can be made sensitive to this corrosion by an improper annealing processing that would prevent the development of niobium carbides hence making carbon more available to precipitate intergtranularly similar to chromium carbides by a subsequent sensitizing processing. 

Integranular corrosion of alloy 625 due to sensitization of the grain boundaries is observed by annealing the alloy specimens at different temperatures and then subjecting them to sensitizing temperatures in the range of 704oC to 871oC for one hour. The specimens were then evaluated in boiling 65% nitric acid permitting the subsequent precipitation of chromium carbides at the grain regions when Inconel 625 is subjected to sensitizing temperatures up to 871oC. At lower annealing points, Niobium carbides are precipitated hence sensitizing heat processing of 704oC to 871oC will result into nominal or no precipitation of chromium carbides at the grain regions.

Performance in Bleach plant environment

Pulp and paper bleach plants involve the exposure of materials in solutions of pH 1.4 to 9.5 with 5500pm chlorides at 80oC and strong chlorine base oxidizers present. It is found that Inconel 625 is one of the best highly corrosion resistant alloys in bleach plant conditions. High chromium and molybdenum content of Inconel 625 result into its pitting resistance in this environment and pitting resistance in general.

Sea water corrosion

Different alloys have been classified by order of corrosion resistance to marine conditions. Inconel 625 is the best in marine environments owing again to its high chromium and molybdenum concentration. Inconel 625 shows supreme corrosion-fatigue strength in sea water.

Aqueous corrosion

However Inconel 625 is popular for its aqueous corrosion resistance, performance of Inconel 625 in high temperature oxidation conditions is good. A cyclic oxidation test is often conducted on high temperature alloys like Inconel 601, Inconel 617 and MA 956 to determine their scale adherence. The test was conducted at 982oC in which the alloy specimens were heated for 15 minutes and quenched in air for 5 minutes. Their weights were measured after each set of 10 cycles to determine the mass change. The samples were evaluated for 40 days. It is found that Inconel 625 offers the supreme resistance to cyclic oxidation showing its potential t retain a security oxide coating under the extreme cyclic condition.

Chlorine

Chlorine is a used as a key material in multiple industrial processes for example mineral chlorination, vinyl chloride production, fuel element processing and heat recovery systems. Inconel 625 shows the best corrosion resistance at the high temperatures such as 593oC to 927oC preventing liquid phase corrosion.