Valuable metals, like NiMo alloys, surround us every day, and professional scrappers can take advantage of this fact to make a tidy sum. But even though scrap metal can be found practically anywhere, locating the most valuable metals takes a keen eye and some expertise.
In general, the metals that offer the best return are locked inside alloys and especially high-performance alloys. Nickel-molybdenum alloys, for example, are prized for their composition and their excellent performance, which makes them a standard choice for a variety of superalloys.
When possible, scrappers should target these alloys, as they contain several metals that are in high demand.
Nickel and Molybdenum
This book is focused on nickel-molybdenum alloys otherwise known as NiMo alloys, and for good reason. There are hundreds of these alloys, found in so many applications that dedicated scrappers should have no trouble finding them. But what makes nickel and molybdenum so valuable? What’s the story behind these two metals? Let’s take a closer look at them, as their physical and chemical properties are what make them so useful.
- Nickel – Nickel is a silver-white metal that is soft, at least compared to most other metals. At around room temperature, nickel is magnetic, a property it shares with only three other elements. It is not a particularly rare metal, and the best estimates of the world’s nickel content run close to 130 million tons. That’s about twice the current reserves of the metal.
It’s somewhat difficult to track the use of this metal throughout history, as it was mistaken for silver, given its similar appearance. It was formally “discovered” in 1751, but it has been isolated from ancient bronzes, some of which date back to 3500 BC. Today, it is predominantly used in alloying applications and is most often found in nickel steel compositions. However, about 1/3 of all nickel is instead used in nonferrous alloys, many of which are considered high-performance alloys.
Nickel is an ideal alloying metal for several reasons. It improves the toughness and tensile strength of most materials, but what makes it truly a standout metal is its excellent corrosion resistance. Environments that would quickly embrittle iron and steel have little effect on nickel, and it is especially capable of handling typical atmospheric conditions, freshwater submersion, caustic alkalis, and many nonoxidizing acids. This broad-spectrum corrosion resistance means it can stabilize other metals and perform in extremely punishing environments.
Finally, nickel can accommodate an impressive range of alloying metals, which allows for a larger selection of alloying compositions. There are hundreds of nickel-molybdenum alloys, and this is the primary reason why.
- Molybdenum – Molybdenum is a silver-grey metal that is a bit harder than nickel, coming in at a 5.5 (out of 10) on the Mohl’s hardness scale. Molybdenum is very well suited for extremely high temperatures, with a melting point of 4,753 degrees Fahrenheit. That means it has the sixth-highest melting point of all elements. It doesn’t even start oxidizing until the 570-degree mark, so it remains inert even as the heat is turned up. But perhaps more important is its extremely low rate of thermal expansion, as this keeps it stable in applications that demand precision.
Like nickel, molybdenum was once mistaken for other materials – notably lead and galena. It was officially “discovered” just a few decades after nickel, though it had been intentionally alloyed with steel as early as the 14th century. A few Japanese swords that contain the metal attest to this, but that particular form of sword making did not spread beyond local use.
While industry quickly found plenty of uses for nickel, shortly after its discovery, the same was not true for molybdenum. Molybdenum is much rarer than nickel, ranking 54th in terms of global abundance. This made it tough to find, and it didn’t help that the metal was hard to extract from its ores. A little more than a century after it was isolated, it was finally incorporated into several applications, mostly owing to its strong ductility. However, it wouldn’t be until World War I when its alloying capabilities were respected.
Also like nickel, almost all processed molybdenum is used in alloying applications. It is most often found in structural and stainless steel alloys, but about 5 percent is incorporated into superalloys, where its high-temperature resistance makes it a valuable addition.
NiMo Alloys and Where to Find Them
That’s a brief look at what makes nickel and molybdenum, or NiMo alloys, so attractive to metallurgy experts. But what does it mean for scrappers? Simply put, scrap recovery experts must be ready to find and process the kinds of alloys that are used in demanding industries. Some of these alloys are superalloys like Inconel and Incoloy, but most are alloys like stainless steel, which are ubiquitous and critical to everyday life. Here’s a brief look at some of the most common alloys and superalloys a scrapper is likely to encounter.
- Stainless steel alloys – Stainless steel alloys make up the vast majority of the alloys that molybdenum is added to. There are hundreds of stainless steel grades, and the only single defining feature of stainless steel is that it contains chromium as well as steel. Not all stainless steel contains nickel and molybdenum, and when molybdenum is added to stainless steel, it’s usually in small amounts – specifically, one to seven percent. A minimum of eight percent is needed in stainless steel alloys.
- Nickel is required to maintain the austenitic properties of the alloy in normal atmospheric conditions. Austenitic stainless steel makes up about 75 percent of all industrial stainless steel applications, as it offers superior mechanical properties to ferritic stainless steel. The nickel acts as a stabilizer in this regard, maintaining the face-centered cubic structure that is emblematic of austenitic stainless steel. Austenitic alloys, compared to ferritic alloys, are tougher, more ductile, and offer better weldability. In short, austenitic alloys are needed when extensive shaping and welding is required, and when impact and abrasive resistance are important.
If austenitic and ferritic stainless steel alloys are on a continuum (which isn’t exactly true, as there are a few other varieties of stainless steel, though they only make up about two percent of the remainder), then nickel and molybdenum sit on opposite ends of the spectrum. Nickel, again, is an austenitic former while molybdenum is a ferritic former. The addition of nickel offsets molybdenum’s effect on crystalline formation, ensuring that the alloy maintains the proper cubic structure.
So why bother with molybdenum, then? It comes down to corrosion and high-temperature resistance. Molybdenum is a large atom and is ideal for a process known as solid solution strengthening. When added to a crystal lattice, molybdenum effectively locks the lattice in place. If the alloy is subjected to extremely high temperatures, it will not suffer from rapid plastic deformation as the molybdenum resists being pulled away from its position. Molybdenum also provides enhanced corrosion resistance (nickel does as well) and is particularly adept at preventing pitting.
Stainless steel is economical to produce and with its well-rounded durability, it is found in an incredible number of applications. Chemical processing plants, oil & gas facilities, petrochemical processing facilities, engine components, pressure-bearing components, kitchen appliances and surfaces, piping systems, pumps, conveyors, aerospace components, utensils, and surgical instruments – and the list goes on.
- Inconel – Inconel is an austenitic superalloy, known for its excellent strength at all temperature ranges. Inconel comes in several varieties, all of which contain nickel, and a few of which contain molybdenum. It is built for the most extreme environments imaginable, as it is highly resistant to oxidation, corrosion and heat deformation.
Inconel’s performance would be overkill in most applications, but it is prized in the automotive, aerospace, and oil & gas industries. It serves admirably in rocket boosters, racing vehicle exhaust systems and engines, and gas turbines. For scrappers, reliable sources of Inconel include racing vehicles, diesel engines, and turbines.
- Incoloy –Like Inconel, Incoloy offers superior corrosion resistance and reliable strength at high temperatures. It is only available in a handful of varieties, and only Incoloy 020 is a true NiMo alloy. However, it is a highly useful alloy, as it offers superior resistance to sulfuric acid, as well as strong resistance to nitric acid, phosphoric acid and chlorides. This across the board resistance to corrosive materials makes it a good fit for heat exchangers, mixing tanks, piping, valves, pumps, fittings, pickling equipment, and fasteners.
- Hastelloy – Hastelloy is one of the most common superalloys in use, as it offers an excellent combination of durability and economy. Hastelloy, in addition to its stability at high temperatures, is highly resistant to chlorine, salts, and oxidizing acids. It serves well in any application where the repeated thermal shock is expected.
Also notable: Hastelloy is particularly weldable and ductile, so it can be fabricated into a huge range of components quickly. This makes it a standard material choice for producing small components like springs, seals, fasteners, and bolts. It is used extensively in the aerospace and chemical processing industries.
What’s in This Book?
By now, it should be clear that NiMo alloys, whether they come in the form of stainless steels or superalloys, are a valuable target for scrappers. But with hundreds of NiMo alloys in use in dozens of industries, targeting them can be a major source of frustration.
That’s where this book comes in. Inside is an exhaustive list of every NiMo alloy worth hunting for, including stainless steel alloys, Inconel, Incoloy and Hastelloy products. Every relevant grade of each alloy is also presented, as some alloys are available in several grades that can be tough to tell apart.
Each alloy entry comes with a breakdown of the alloy’s composition, by element. This will help in properly valuing alloy scrap. In addition to composition, each entry also lists the relevant characteristics of the alloy, including its mechanical properties, corrosion resistance, and magnetic properties. These can aid in alloy identification. Finally, every entry details the most common applications associated with each alloy. This can help scrappers pinpoint industries that make use of a particular alloy, helping narrow down targets for scrap recovery.
Some Words of Caution
Scrappers that have graduated to NiMo alloys are likely equipped to manage tons of material at once. It is essential that scrappers intending on hunting down NiMo alloys have plenty of manpower and equipment on hand to process a lot of miscellaneous material and waste. Valuable alloys are typically found inside vehicles, aircraft, appliances, heavy machinery and other hard to crack items. This the kind of job best left to scrappers that have metal processing expertise on their side.
That being said, reference materials like this book can go a long way in identifying and categorizing alloys for scrapping purposes. Keep it on hand, and you’ll be ready to tackle any NiMo alloys that come your way.