Alloys for Offshore Applications

Interview conducted by G.P. ThomasMar 31 2014

Ian Moody, Product Manager at Columbia Metals, discusses the offshore applications of the NIBRON alloy and how this is produced.

Could you please start by giving a brief introduction to Columbia Metals and the sectors that you work within?

Columbia Metals was started in 1961, so it’s been going for over fifty years. It’s a family-owned, non-ferrous stockholding business, and we stock a wide range of copper alloys; bronzes, brasses, and low expansion alloys. More recently we’re moving into nickel alloys which are used in offshore applications.

We’re positioned in three places in the UK, with warehouses in London, Earls Barton, and Halifax, and we service an extremely wide range of industries, both domestically and internationally.

The main sectors that we’re concentrating on currently are oil/gas and aerospace. At the same time, we’ve got a lot of material going into the automotive and architectural industries.

We also still get a lot of inquiries from small ‘niche’ businesses - architects, blacksmiths, and sculptors appreciate some of the older bronzes and brasses due to their appearance and workability.

The NIBRON SPECIAL® is your flagship alloy range – could you go into a bit more detail regarding this?

The NIBRON alloy originated back in the ’80s and ’90s, and was a development that came out of the Ministry of Defense when they were looking for strong nickel-aluminum alloys that they could use in naval vessels and submarines.

In terms of its chemistry, it can be classed as enhanced cupronickel, from the nickel-aluminum-bronze family. It’s primarily copper, with about 14.5% nickel, and then small additions of manganese, aluminum, and iron which raise the strength levels way above what you get with a normal or standard 90/10 or 70/30 cupronickel.

At the same time, you keep enough ductility in the metal, so it can be a useful engineering alloy. It’s very simple to raise the strength of the alloys, but if that’s done at the expense of ductility, then you’re not left with a workable material at the end.

NIBRON nickel-aluminium-bronze alloy.

Could you go into more detail regarding the physical properties of NIBRON, and how these are important in offshore industries such as shipping?

The key physical property of NIBRON is its very high strength. Compared to most copper nickels it’s considerably stronger with a yield strength of over 550MPa, which is unusual for a copper alloy.

This is balanced with excellent wear resistance and excellent galling resistance so it’s useful in applications where there are moving and rotating parts rubbing together. It doesn’t suffer from galling, where it will stick to itself, or indeed stick to other metals it might be in contact with it. Obviously, being a high copper-nickel alloy, it’s also got exceptionally good corrosion resistance.

One of the areas I think is important when you’re considering NIBRON is that it’s completely immune to hydrogen embrittlement. This is key in offshore applications, particularly in gas industries, where processing sour fluids with hydrogen sulfide in the environment, can be very bad for high tensile steels.

NIBRON is extremely useful in offshore applications.

So it’s this resistance to hydrogen embrittlement that makes NIBRON so useful to oil and gas industries?

Absolutely. You’ve got this resistance to hydrogen embrittlement, but also excellent general corrosion resistance, not just to hydrogen, across a wide range of different environments. One thing that the company has done historically with NIBRON is tested its performance against a number of different environments. These include ammonia and amine-containing environments, which often cause problems for metals. Columbia Metals have technical reports available that can substantiate the performance of NIBRON in some of these environments, and we make those available to design engineers to help them to justify their selection choices.

How is NIBRON unique compared to other alloys that are used in similar applications?

There are a few similar proprietary alloys that are available from our competitors, but NIBRON stands out in the sense that it does have a unique composition and it‘s manufactured to quite an old German standard.

In terms of what NIBRON might compete with, you have high strength steels, some stainless steels, super duplex steels, and if you go to even higher strength levels you might find yourself competing with high nickel alloys.

Often, it comes down to a combination of factors as to what a designer will choose as being the right material for the job. It will be a combination of strength, corrosion performance and obviously cost.

Could you give a brief outline of how the NIBRON alloy is manufactured and processed?

First, you have to understand what NIBRON is. In terms of its matrix, it’s a single-phase material, not a dual-phase material. This comes from the complete solubility of nickel in a copper matrix. So it’s a single phase matrix which is strengthened by a very fine dispersion of Ni₃Al precipitates.

In order to get that sort of structure, we start with an electric arc melted ingot, which will then be vertically cast to remove the potential for oxide entrapment and gas. We try to keep the material as free from inclusions and impurities as possible at the casting stage. Those ingots will then subsequently be reheated into the forging range, around 1000^oC at the start and you can then forge down to about 850^oC.

When you forge you need a sufficient reduction in area, so you’re doing enough work to come up with a completely wrought structure at the end. The cast structure that you have had from the ingot casting, should be completely broken down and turned into a completely wrought structure.

Once you’ve got this structure, you can take the bar down further, if you want a smaller bar, by hot extrusion. So really the production process is dependent in part upon the final size of bar you’re looking to create. It could be done by hot forging, or by a combination of forging and extrusion.

One thing with NIBRON is, once you’ve got your bar, it is hot workable, and if you heat it back above the recrystallization temperature, you can hot work the NIBRON as long as you don’t cool it too quickly.

You wouldn’t then subsequently want to quench NIBRON, you have to allow it to cool at the maximum rate of about 200 degrees per minute to allow the precipitates time to form because they are key to the performance of the grade.

We have spoken about offshore applications, are there any specifically onshore applications that NIBRON can be used in?

It’s quite a flexible grade, given that is a very high strength, and this gives designers quite a bit of flexibility. For instance, it’s used in aerospace where you need nonmagnetic performance. One thing I didn’t mention before is that NIBRON is almost completely nonmagnetic. So where you have magnetic sensitive applications, and aerospace is a prime example for that, NIBRON is a good alternative to some nickel grades which may have some magnetic permeability. This allows you to use NIBRON for connectors in electrical applications and also automotive engines.

Bronze has traditionally been used, but bronze is not always strong enough. NIBRON does have that additional strength as long as the operating temperature doesn’t exceed about 350^oC. There is an upper limit with NIBRON partly because of its strengthening mechanism. If you have prolonged exposure above 350 degrees, you start to lose the benefits of that precipitation hardening, and very quickly the ductility drops off, and you’re into an area where you don’t want to be using the material.

Going the other way, it is stable right down to cryogenic temperatures. So unlike steel, for example, copper alloys don’t embrittle at cryogenic temperatures, so they retain their toughness.

Is there anything else you particularly want to discuss in terms of the trademark alloys that Columbia Metals produce? Are there any specific case studies that you’d like to highlight that recently happened?

Another alloy we produce is TROJAN, our ultimate super strength copper nickel silicon alloy. This has been specified by a number of the Formula 1 teams, for valve guides and valve seats, and the F1 engines. Now I know they’ve just gone through a complete revamp of the specifications, so whether that is still the case, I can’t say. But certainly, under last years’ rules, it was quite widely used.

COLDUR-A®, sometimes known as architectural bronze, is a high copper alloy that is very popular as it’s one of the most easily workable alloys. Very popular with sculptors and with metalsmiths, it is used all over for things like nameplates and signs. One of our country’s premier artist blacksmiths is going out to give a quite prestigious lecture in the States at the moment, and he’s taking some COLDUR-A with him to demonstrate its workability.

What does the future hold for Columbia Metals? Will you continue to look at new alloys and new compositions?

Columbia Metals has had a stable range of trademark alloys that hasn’t really been growing recently. I have come in with a remit to try and expand that range, and I look at it in two ways. Firstly, incremental developments to the alloys we’ve got at the moment, so minor enhancements that will keep those alloys in designers’ minds. This will be coupled with looking at a couple of completely new additions to the range - maybe a couple of novel alloys that aren’t really available at the moment.

The one problem that I have in terms of alloy development is that we don’t have our own production facility here, so I am dependent on partner companies that are willing to share the risk and potentially the rewards with their development work. So, I need mills who are prepared to work with us, and some of the work may be done at academic institutions in the UK, where we can get small quantities of test alloys manufactured.

What I do think we need to do now is improve our holdings on the sort of alloys that are more relevant to current growth industries, such as the oil and gas and aerospace industries.

There are ideas for the future and it seems to be quite an exciting period of growth for the company - for instance, we just recently decided to bring in our own ultrasonic testing facilities, which we didn’t have in the past.

About Ian Moody

Ian Moody is a metallurgist with almost 20 years of industrial experience. He left Imperial College in 1995 with a Ph.D. in pyrometallurgy and joined British Steel (later renamed Corus and now Tata Steel) where he worked for 18 years in a variety of roles including customer support metallurgist and ultimately 10 years as the technical manager for the international projects team.

The international projects team traded the complete range of steel and non-ferrous products to clients in the European, North American, North and West African, Middle Eastern and Asian regions. They serviced a wide variety of industries including oil and gas (both onshore and offshore), major infrastructure (bridges, stadia, airports), automotive component manufacturers as well as smaller niche markets.

His team was responsible for all technical and quality matters including material sourcing and supplier auditing, preproduction technical specification and post-production technical documentation and quality disputes. Leaving Tata Steel in 2013, Ian is now the Product Manager at Columbia Metals, responsible for all technical matters, quality, and new product development. Columbia Metals currently have a domestic focus but a strong intention to grow our international presence.