Technical library
Choosing between two alloys is rarely about which is better. It is about which failure mechanism you are designing against, and what that resistance is worth.
Four failure patterns — pitting, stress corrosion cracking, acid attack, creep — and the upgrade each one calls for, with cost multipliers.
Inconel is for temperature, Hastelloy is for acid. Chemistry, service limits and the grades under each brand.
More molybdenum or more chromium: reducing acids against oxidising media, and which welds more forgivingly.
Why the alloy with twice the yield strength has the lower temperature ceiling.
Three times the molybdenum against a copper addition — and why the cheaper alloy wins in sulphuric acid.
Seawater service: immunity to chloride cracking against double the strength at half the price.
Every comparison here starts from the same place: the medium, the temperature, the pressure and the governing specification. Without those four, any alloy recommendation is guesswork — and in special alloys a wrong selection usually shows up months after commissioning, as an unplanned shutdown rather than a rejected delivery.
Where a less expensive material will do the job, we say so. We do not hold stock we have to move, so there is no reason for us to push the costlier grade.
Send us the operating temperature, the medium and the pressure. We will come back with a material recommendation and the cost difference between the two options.
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