The evolution of nickel alloys and welding materials
Since he first heard his uncles discuss the nickel-plated bumpers and hubcaps on their 1937 Plymouths, welding expert Carl Smith has witnessed the use of nickel and its alloys evolve. Long used in the energy sector, the materials have seen an increase in popularity because of EPA regulations.
The first time I remember hearing the word nickel was in the 1940s. My uncles were discussing the differences between their 1937 Plymouths (Figure 1). One uncle was of the Mennonite sect, and the other was a Baptist. The Mennonite uncle had painted over his Plymouth’s nickel-plated bumpers and hubcaps as was consistent with his belief. The Baptist uncle spent most Saturdays polishing his bumpers, grill, hubcaps, and spotlight.
This discussion had me thinking that maybe the car manufacturers melted down 5-cent pieces (nickels) and dipped the car parts in the liquid, much like my grandfather dipped his chewing tobacco in molasses.
Of course, today these car parts are referred to as chrome-plated. There is still a significant connection between chromium and nickel in stainless steels. I just always knew that the nickel was shiny when polished. I had no idea what a nickel alloy was until years later.
Repairing a Problematic Tractor Part
I was the neighborhood welder/repairman in my small community comprising a few hillside farms and 8N Ford tractors. One small part on the tractors broke nearly every year. The drawbar that lifted the plows and rakes contained a cast-iron part that was similar to the ball receiver on a trailer hitch. The hillsides put a tremendous strain on the receiver. I must have used 20 pounds of Oxweld #25M brazing rod each summer. This same part would break over and over.
One of my uncles (I had 18) worked at the nickel plant in Huntington, W.V.—the International Nickel Company, INCO. He was having lunch with a group of co-workers, one of whom worked in the welding laboratory, when he began telling a fellow farmer about the problem with the receiver continually breaking. The worker from the welding laboratory suggested that my uncle try an electrode called Nirod. He got us a few electrodes to try. The only problem was that I didn’t have an electric welding machine.
A neighbor had an AC transformer welder, but the Nirod electrode required a DC welder. My uncle was a “horse trader,” so he traded a set of plows for an old Hobart DC gasoline welding machine with a Willys Jeep engine that needed to be rebuilt. The whole neighborhood came together and rebuilt the engine, which still runs today.
I heated and wire-brushed the first experimental receiver to remove all the brazing material. I ground a V in the crack and welded the part. I didn’t really trust the electrode, since brazing was all we had ever used. I added two transverse welds across the V weld to be safe. We decided to put a hay bailer on the tractor to test the weld. The driver gave it a workout, twisting and turning the tractor to see what would happen. It held.
From that day on I was sold on Nirod. It created lasting welds, even on water well pump parts that cracked from freezing in the winter cold. This welding material was new to me, but not to industry. That was the beginning of my long and successful association with nickel. However, at that time I was not aware of all the other nickel products the INCO plant produced.
Learning on the Job
My first welding-associated job was with a company called Virginia Welding. The most important part of my job was to recommend and demonstrate various welding products. Since I had some hands-on training at the Hobart Institute for Welding Technology, this position was just right for me.
I frequently leaned on the INCO people, who were extremely knowledgeable about welding dissimilar metals, a topic of foremost interest in West Virginia’s mining industry. Welding a dozer blade made of high-carbon steel to a bucket made of medium- or low-carbon steel was just one of the problems. Questions brought to the INCO laboratory were answered or researched to find solutions.
I was allowed to take my problem welds into the laboratory and observe the lab technicians as they created procedures related to my particular needs. I was able to take notes as to the welding variables, materials, and techniques that best suited the task at hand. Even though these experiences occurred in the early ’60s, I could still name most of the people (I fear that I may miss a name) who led me through the proper methods for making the correct welds for my customers.
Later I became a welding specialist and quality manager for one of the oldest and largest fabricating shops in our state. This company secured several jobs that required nickel alloys and help from the INCO laboratory. This is when I really discovered the many uses of nickel and the many nickel alloys. Until then, I had dealt only with a few of the alloys used for dissimilar welds or building up shafts.
I was so intrigued by nickel that I did some personal research into its history. I found that an alloy consisting of carbon steel and 36 percent nickel, now known as INVAR®, was discovered in the late 19th century. A French scientist named Charles Guillaume, who was involved with weights and measures, was searching for a material that would have a low coefficient of thermal expansion.(minimal expansion and contraction). This material would need to serve well in maintaining the dimensions required for precise measuring devices. Invar is excellent even in extreme cold (cryogenic) temperatures. It also is used for circuit breakers and mounting telescope lenses.
Nickel is known for toughness. It often is added to carbon steel alloys to create toughness, sometimes called impact resistance. Charpy impact values are greatly enhanced by the introduction of nickel into several material types.
Nickel also enhances hardenability. Even some of the copper alloys, such as aluminum bronze, contain nickel for increased strength, toughness, and corrosion resistance. These materials are commonly found in hydrogen coolers for power plants (Figure 2), propellers for watercraft, and pump parts.
Other alloys have been developed for seawater atmospheric corrosion resistance. These are commonly referred to as cupronickel. Welding materials, both wires and shielded metal arc welding (SMAW) electrodes, have been developed for these alloys). They range from 70 percent Cu/30 percent Ni to 90 percent Cu/10 percent Ni.
The 70 percent Cu/30 percent Ni is not to be confused with the 70 percent Ni/ 30 percent Cu that INCO developed and named MONEL®. The MONEL alloy has higher strength and better heat resistance and serves very well in freshwater pumps and related parts such as impellers (Figure 3).
The electric power industry has always been a rather consistent user of nickel and its alloys. Recently, usage has increased because of EPA regulations and the industry’s desire to be good neighbors. Scrubbers (Figure 4), or fluidized gas beds, require nickel both in the duplex stainless alloy absorbers and in the alloy 276 piping that is placed inside the units.
Most fabricators have begun to use INCONOL® 625 or the equivalent to prevent deteriorating welds on the units. These NiCrMo-X wires or electrodes have been proven to last about five times longer than duples. The duplex welding materials fail predominately in the heat-affected zone (HAZ). These are huge fabrications, and most companies can ill afford to replace the welds.
Probably the most interesting project that I have experienced with a nickel alloy was in the 1990s. A research group in the tristate area of West Virginia, Virginia, and Tennessee embarked on a venture to convert coal and oxygen to hydrogen. This involved a vessel with 6-in.-thick walls, 24 in. in diameter, and approximately 20 ft. long (Figure 5). The unit was made from INCO 800HT® and welded with ERNiCrMo-3 (INCO 625). Our job was to weld the reduced section at the ends and the retaining bars to hold the bolt-on heads in place. The unit was hydrostatically tested at 2,000 PSI. The hydrogen gas that was produced eventually was tested to propel a D-9 Caterpillar tractor pushing a 20-ton load. The result was a success, but the research was scrapped because of cost inefficiency.
Another interesting project was building parts from 800HT welded with ERNiCrMo-3 for a Central American aluminum refractory plant. The material was 2 in. thick and required 31 passes with 0.045-in. wire and a shielding gas mixture of 65 percent helium/35 percent argon. Our company welded it with no defects using 1,200 pounds of wire (Figure 6).
It is obvious that my experience with nickel, beginning with Nirod, has come a long, long way. There are more advances with the nickel alloys than can be written about in a short article. INCO and the Nickel Development Institute (NIDI) deserve credit for the great innovations in nickel. For those who lean toward printed material rather than the Internet, NIDI has published an excellent book written by C.P. Dillon entitled Corrosion Control in the Chemical Process Industries. It is a good reference for anyone who is interested in learning more about any form of corrosion, not just in the chemical industry.