Tungsten vs. Molybdenum as Base Materials for Plating
As refractory metals, both tungsten and molybdenum are prized for the characteristics inherent to this category, such as corrosion resistance, excellent conductivity and an extremely high melting point. Nevertheless, these heavy metals do have some distinct differences that affect their suitability for various applications.
When to Choose Tungsten
Tungsten is an incredibly dense, silvery metal that is used extensively in industrial applications thanks to its exceptional hardness. In spite of its strength, it is also extremely ductile and can be drawn into fine wires. Tungsten has the highest melting point of any metal at over 6,170 degrees, and it is virtually impervious to acid.
In spite of this high melting point, however, tungsten does develop a volatile oxide film when it reaches red heat, or approximately 538 degrees. This means high-heat applications require tungsten to be plated with another material to receive the greatest benefit from its other properties.
Plating onto tungsten is inherently challenging due to the reactive nature of refractory metals, making it impossible to suspend the workpiece in an aqueous bath. It requires the expertise of a skilled and experienced metal finishing company like SPC to execute the task correctly.
When you need a heavy metal with the absolute best in heat resistance and conductivity, plated tungsten is an ideal option. Plating onto tungsten is a multi-coat process, first requiring a layer of rhodium. After this, materials such as chromium, nickel, silicon or precious metals can be applied depending on the application requirements.
When to Choose Molybdenum
Silvery in color and with a brittle texture, molybdenum has a melting point of 4,753.4 degrees, a number exceeded by only five other naturally occurring elements. Like tungsten, molybdenum is classified as a heavy metal, although it has a lower density than tungsten. Because of this characteristic, some manufacturers prefer molybdenum for their applications.
Molybdenum also has one of the highest thermal conductivity ratings, which is complemented by its possessing the single lowest coefficient for thermal expansion of any element. These characteristics and its excellent strength lend it ready to use in industrial motors and applications in the aerospace, electronic and electrical and military and defense industries.
Much like tungsten, however, molybdenum does come with certain challenges. The use of this metal in high-heat environments requires it to be coated for optimal resistance to corrosion. Due to its reactivity, plating onto molybdenum requires an expert application of the coating material to the substrate. Fortunately, numerous coatings are compatible with molybdenum, including nickel, precious metals, glass and chromium.
If your application calls for a combination of strength, heat resistance and minimal thermal expansion, plated molybdenum is an exceptional choice. With a coating to stave off corrosion, molybdenum will reliably tolerate and convey heat without softening or expanding.
Get a Free Plating Quote on Your Material of Choice
When you need plating performed on challenging heavy metals like molybdenum or tungsten, you go to the experts. SPC is a full-service, socially responsible metal finishing company that prioritizes development and quality over volume, and we have the patents and testimonials to prove it.