Molybdenum Heating Elements
H.C. Starck’s molybdenum is a superior, pure and alloyed refractory material for heat treating medical, aerospace, defense and automotive products in high temperature furnaces that include medical devices, aircraft and aerospace components, nuclear fuel pellet production, and high pulse magnet research applications. Our innovative materials improve cycle-time and maintain temperature uniformity with no carbon contamination, less rejection of components, better handling and reduced production cost compared to graphite and ceramics for a wide spectrum of metal injection molding applications.
For higher temperature heat treating applications such as hardening or brazing, molybdenum is the preferred heating element material. For specialized heat-treating applications above 1,482 °C (2,700 °F), refractory metals such as molybdenum, tantalum or tungsten are good choices. Other processes such as low pressure vacuum carburizing use graphite or silicon carbide elements.
Almost all high-temperature vacuum furnaces are electrically heated. Resistance heating elements are constructed from refractory metals in a variety of styles. Today all high-tech metallurgy technology operates in vacuum atmosphere with high temperatures from 1,150 oC up to 2,800 oC.
Recrystallization and High-Temperature Warpage Resistance
Molybdenum-lanthana (MoLa) alloys are one type of oxide-dispersion strengthened (ODS) molybdenum containing molybdenum and a very fine array of lanthanum trioxide particles. This combination creates extraordinary characteristics of the material, which demonstrate resistance to recrystallization as well as high-temperature warpage. Molybdenum-lanthana is an ideal material for applications requiring dimensional stability and strength at temperatures above the capabilities of either pure molybdenum or molybdenum TZM alloy.
H.C. Starck manufactures MoLa alloys in three levels of doping with lanthanum trioxide: 0.3 weight %, 0.6 weight % and 1.1 weight %. The trioxide particles stabilize the grain structure of the material creating very beneficial high temperature performance. The unique H.C. Starck doping process of introducing the oxide particles to the molybdenum matrix is key to the excellent properties obtained, and differentiates H.C. Starck from other manufacturers of similar materials. In addition, the doping process maximizes the homogeneity of the lanthanum oxide dispersed in the molybdenum matrix.
Benefits of H.C. Starck’s MoLa Alloys
MoLa alloys have great formability at all grade levels when compared to pure molybdenum in the same condition. Pure molybdenum recrystallizes at approximately 1,200 °C and becomes very brittle with less than 1 % elongation, which makes it not formable in this condition.
MoLa alloys in plate and sheet forms perform better than pure molybdenum and TZM for high temperature applications. That is above 1,100 °C for molybdenum and above 1,500 °C for TZM. The maximum advisable temperature for MoLa is 1,900 °C, due to the release of lanthana particles from the surface at higher than 1,900 °C temperature.
The “best value” MoLa alloy is the one containing 0.6 wt % lanthana. It exhibits the best combination of properties. Low lanthana MoLa alloy is an equivalent substitute for pure Mo in the temperature range of 1,100 °C – 1,900 °C. The advantages of high lanthana MoLa, like superior creep resistance, are only realized, if the material is recrystallized prior to use at high temperatures.