Selecting materials for aerospace components is always a balancing act for engineers. An aerospace engineer needs materials with the strength to withstand the extremes of aerospace travel, but the materials also need to be workable enough to machine into the complex shapes needed for various components. The materials need to be consistent and durable to reduce excessive weight penalties, and most importantly, the materials need to be reliable. This is a need driven by the fact that there are lives in the balance.
This is where 15CDV6 stands out.
What is 15CDV6?
15CDV6 is arguably the most well-known low-alloy steel used in the aerospace industry, especially in the European aerospace manufacturing industry. The low-alloy steel gets its name due to the fact that it contains, by weight, approximately 0.15% carbon and a combination of alloying elements, such as chromium, molybdenum, and vanadium. Other regions of the globe may use other naming standards for the same low-alloy steel. For example, it may be referred to as 1.7734 in certain German standards or 16NCD13 in certain French specifications.
What makes 15CDV6 such a prominent low-alloy steel and a staple in the aerospace industry is not one spectacular feature. It is, rather, the combination of a multitude of characteristics that makes it rather useful across varying applications. It is not a thoroughbred to boast and brag about. It is in fact a very reliable workhorse.
Essential Attributes
15CDV6 shines not in its design but in its mechanical properties after heat treatment. Case hardening, in general, is able to produce tough cores with significantly harder surface layers. This creates components with a tough material on the outside that resists wear and fatigue, but a ductile core that absorbs shocks and stresses without fracture.
Appropriate heat treatment yields tensile strengths between 900 and 1100 MPa. The specific processing and section thickness does influence this range, but it is a general standard that can be relied on. The material also pairs its mechanical properties with machineability in its annealed condition. This is very important as processing complex geometries through machining consumes time and tooling.
The predictability in the steel’s response to heat treatment creates a lower likelihood of production issues. The need for this type of production efficiency rises as the critical components we are dealing with become more complex.
Typical Uses in Aerospace
15CDV6 is used in aircraft and helicopter systems, regardless of visible applications. Major use in landing gear parts, pins and bushings. These structural elements need to be able to endure multiple repetitive loading cycles. Their engineering provides good surface hardness and toughness.
Another common application of this material is in transmission systems. It’s common to find sets of gears and shafts that have these materials. Their engineering provides toughness and wear resistance, enabling the gear/shaft sets to endure the shock and wear created in the operation.
15CDV6 is used in some engine accessories and mounting systems. In some of these systems, the weight is somewhat less critical than other primary structures, but still high performance is a must. These materials have also been engineered to endure the mechanical and thermal stresses of working near powerplants.
Working with 15CDV6 requires attention to the parameters of heat treatment. When case hardening is needed, the common practice is to do a carburizing cycle at 900-930°C, followed by the quenching and tempering process. For the cycle to end with a case depth and core properties that match the needs of the case, there are parameters that must be followed; otherwise, the results can be a trouble.
In the annealed state, materials cut pretty well with normal tooling and at normal operational parameters. Once materials are hardened, you are most often restricted to only using grinding operations to achieve final dimensions. Though, this is a pretty standard practice for most case hardened steels.
Care is also needed when welding this material. Cracking can be avoided with preheating and controlled cooling, but then the question is, is welding really the best option for your application? In some cases, if the situation allows, mechanical fastening and other joining methods maybe be more suitable.
Supply Chain and Specifications
The supply chain of materials for 15CDV6 can be a bit tricky, but with proper planning you can source this material anywhere in the world including Europe. They often have this material in stock, but because the aerospace supply chain is global, even with low stock you can still find this material with the proper planning. Depending on the form, dimensions, and other market variables, lead times can vary a lot.
This steel falls under a variety of aerospace material specifications. The similar steel standard for Europe is called EN 10083, and you can find this under aerospace material specifications for most of the manufacturers. It is mandatory for aerospace suppliers to have certification and traceability, so make sure to check if your supplier can produce these documents.