Figure 2 ws nQuestion: Staining of titanium parts after vacuum heat treatment following a gas quench, your thoughts on possible causes and remedies? 

In response to this question, phenomenal suggestions by everyone! A wealth of great information here. So, what else could be happening? Let The Doctor add a few thoughts to the discussion. First, the fact that the discoloration (staining) is brown in coloration suggests that the oxide is forming on the part surface during cooling when the temperature is in the range of (approximate) 245ºC – 270ºC (475ºF – 520ºF). This is supported by the fact that the oxidation does not occur “during natural cooling” (which we assume to mean cooling under vacuum). Second, the fact that the discoloration is more evident at the bottom of the load suggests the phenomenon is (gas exposure) time dependent, that is, the longer the parts take to cool through the critical range, the greater the chance for discoloration. Third, a “steel-copper-stainless steel” test will be helpful in isolating if it is a water or air leak. Leaks in heat exchangers have been known to “open up” during the cooling cycle when exposed to hot gases and close up again at room temperature. The writer has personally experienced this – the solution being the replacement of the old heat exchanger at which time the problem went away. Fifth, look in all the places suggested by those who responded, but remember to make only one change at a time and evaluate its impact in order to find then correct the problem. Finally, as an unabashed promotion of my books on Vacuum Heat Treatment (Volume II of which comes out this fall), there are a number of sections that discuss this very issue in considerable detail covering subjects such as “Vacuum Furnace Contamination and Cleanup Cycles”, “Leaks External to the Vacuum Furnace Proper” and “Factors Affecting Performance: Discolored Work” to name a few. Good luck!. By Dan Herring

Figure 1 wsThe automotive, aerospace, medical device and construction industries rely heavily on the use of fasteners to secure component assemblies. For example, medical devices (e.g. dental & orthopedic implants, instruments) employ literally hundreds of different types fasteners to hold their assemblies together

Even though the components in the medical devices are small or even tiny, when a fastener fails, the device will almost always fail as well. The correct fastener ensures that the device goes together and stays together for the intended life of the assembly, and that the device performs as desired. Fasteners can overcome challenges in assembly, solve quality problems and significantly reduce the total cost of the device. By Dan Herring 

Figure 2a wsWe study vacuum science and vacuum engineering in order to better understand the role vacuum technology plays in creating useful engineered products (Fig. 1, Table 1). Manufacturing as we know it, and research and development as we have come to depend upon it, would not exist without the creation and control of the vacuum “atmosphere”.

Vacuum techniques are important in both the industrial setting and for the scientific community, whether it be in heat treatment or high-energy physics. At the heart of vacuum processing for manufacturing is the modern vacuum furnace. Ever since the introduction of the electric light at the beginning of the 20th century, society and manufacturing have been linked to advances in vacuum science and engineering. Examples include the development of modern computers to advanced transportation systems; the very fabric of modern society depends on vacuum technology. By Dan Herring 

figure 4 wsVacuum furnaces are available in numerous styles and sizes and come in both standard and custom configurations. They are designed to process an almost limitless number of both semi-finished component parts as well as raw materials using a diverse set of thermal processes in equipment available from a wide variety of different equipment manufacturers located around the world.

The intent here is to provide a brief overview of some of the more common designs and applications found throughout the heat-treatment industry. The hope is that the reader will come away with an understanding that there is a vacuum furnace solution to virtually any design, application or specification encountered.. By Dan Herring

vacaero vacuum furnace wsThe role of materials science (Fig. 1) is to study, develop, design, and perform processes that transform raw materials into useful engineering products intended to improve the quality of our lives. It is said by many that material science is the foundation upon which today’s technology is based and that real-world applications would not be possible without the materials scientist. The discipline has expanded to encompass materials for many highly specialized product applications.

The industrial revolution thrust metals into the forefront of technology, and they have stayed there ever since becoming the very foundation on which our modern society is built. One cannot envision a life where our transportation and communications systems, buildings and infrastructure, industrial machines and tools, and safety/convenience devices that are not an integral part of our daily lives. By Dan Herring 

burn hazard wsWhen problems arise, especially those related to safety, we want to know that we have isolated the root cause and instituted corrective action measures so as to avoid their reoccurrence. 

Worker safety and the safe operation of heat-treat equipment is both MANDATORY and NON-NEGOTIABLE, especially when operating and maintaining vacuum equipment where dangers of asphyxiation, electrocution and explosion are as real as they are with any other type of thermal processing equipment. “It won’t happen to me” is not a phrase that belongs in the heat-treat shop and provides a false sense of security to all involved. There is no substitute for understanding the inherent dangers, taking the necessary steps and placing the right safeguards in place to prevent accidents from happening. Safety and safety issues are a serious matter and should be treated as such by all individuals within the company. By Dan Herring 

Figure 2 wsWhen operating vacuum furnaces, situations may arise in which the hot zone and/or cold walls may become contaminated (Fig. Nos. 1 - 2). This can occur from a variety of sources: air leaks, outgassing from residues left on the parts as a result of the manufacturing or cleaning processes, vaporization of sensitive materials (e.g., chromium bearing materials), process induced contaminations such as carbon in the form of soot or tar, fluxes from brazing pastes, excess braze alloy as well as many other sources. Often times the work being processed is also affected (Fig. 3). The question becomes, how do we attempt to clean up our contaminated vacuum furnaces? By Dan Herring

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