We continue our discussion of ways to improve vacuum performance by understanding how to maximize the operation of our vacuum systems. Tip #5: Diffusion Bonding

Diffusion bonding is a solid-state joining process involving both vacancy and interstitial diffusion of atoms between surfaces in intimate contact with one another. The process is capable of intentionally bonding together a wide range of metal and/or ceramic part combinations, forming strong metallurgical bonds. Applications include hot compacting of oxides, nitrides, borides, carbides, sulfides and their mixtures to near theoretical densities as well as sintering ceramics and powder metals. By Dan Herring

We continue our discussion of ways to improve vacuum performance by understanding how to maximize the operation of our vacuum systems. Tip #4: Maintain Your O-Ring Seals

O-rings are an integral part of any successful vacuum system, however O-rings lose their elastic nature over time and eventually crack (Fig. 1) leading to air infiltration into the vacuum chamber. When replacing O-rings it is critical to use the correct type, normally specific by the original equipment manufacturer. By Dan Herring

We continue our discussion of ways to improve vacuum performance by understanding how to maximize the operation of our vacuum systems. Tip #2: Select The Right Vacuum Level for the Job

When selecting the right vacuum level, one must ask oneself, “What type of vacuum level does my application require?” For example, while many vacuum systems using modern high speed pumps can, in a clean, dry, empty and outgassed chamber, reach vacuum levels as low as the 10^-9 torr range, we must ask ourselves, “Is this level of vacuum really necessary?” Remember, either too low or too high a vacuum level could result in undesirable surface conditions – from vaporization of elemental constituents to oxidation of surfaces causing rework or even scrap. By Dan Herring

We continue our discussion of ways to maintain your vacuum pumps by considering what needs to be done with blowers and diffusion pumps. Vacuum blowers (a.k.a. booster pumps) typically need little day-to-day maintenance, which normally consists of simply monitoring the oil level in the pump. The blower (Fig. 4) is used in conjunction with the mechanical pump to improve pumpdown rates and ultimate vacuum levels. By Dan Herring

A frequently asked question is, “How can I keep my vacuum furnace performing like it was when it was brand new?” This goes hand in hand with the question “How should you operate and maintain your vacuum furnace to maximize your investment and produce repeatable high-quality results?” The next few articles will provide tips for doing just this. By Dan Herring

In vacuum applications, cold traps are added to vacuum pumping systems either to remove unwanted contaminants (e.g. water, solvents, acidic or alkaline compounds) from the gas stream or to prevent pump backstreaming. These conditions can cause loss of efficiency or damage when introduced into or emanating from the vacuum pumping system.

In simplest terms cold traps work by sublimating a gas molecule, that is, by transforming the molecule directly from the gas phase to the solid (crystalline) phase thus bypassing the liquid phase. The gas crystallizes out on a cold metal surface often appearing as “frost” on the trap. By Dan Herring

The long-standing practice by furnace manufacturers of offering only “stand-alone” pieces of equipment is changing. Today, some manufacturers, especially those who manufacture vacuum furnaces are capable of building completely integrated systems, which can be placed directly into the manufacturing flow. Of the choices technology available, only vacuum furnaces offer a true lean, green and agile solution. Let’s explore why.

To begin, we need an understanding of what being lean, green and agile is all about. Lean manufacturing (lean enterprise, lean production) is a production practice that considers the expenditure of resources for any goal other than the creation of value for the end customer to be wasteful, and thus a target for elimination. Working from the perspective of the customer who consumes a product or service, “value” is defined as any action or process that a customer would be willing to pay for. By Dan Herring

Today, tool steel heat treatment is based on a simple premise, that to obtain the optimum performance from any given grade, every step of the heat treating process— including stress relief, preheating, austenitizing, quenching, deep freeze/cryogenic treatment and multiple tempers—must be done exactly correct. Absolute control of both process and equipment variability is one of many reasons why vacuum processing (Fig. 1) is popular in tool steel heat treatment ^[1].

The selection of any tool steel depends on a combination of factors including component design, application end use and performance expectation. For any given application (Fig. 2) the goal of heat-treating is to develop the ideal microstructure to help achieve the proper balance of desired properties (Table 1) namely hot (red) hardness, wear resistance, deep hardening and/or toughness. By Dan Herring

Most of us are familiar with processing in the vacuum range up to around 1.33 x 10^-3 Pa (1 x 10^-5 torr) or slightly lower (Fig. 1). There are also lessons to be learned from understanding the demands of ultra-high vacuum applications (Fig. 2). Let’s explore what’s involved.

What is an Ultra-High Vacuum? Practical high vacuum levels (Table 1) range down to approximately 1.33 x 10-4 Pa (1 x 10-6 torr) while ultra-high vacuum (UHV) levels are in the vacuum range characterized by pressures of about 10-7 Pa (7.5 x 10-10 torr) and greater. These vacuum levels demand the use of special materials of construction and processing techniques such as preheating (i.e. bake-out) of the entire system for several hours prior to processing to remove water and other trace gases, which adsorb on the surfaces of the chamber. By Dan Herring

Experience has shown us that sensitive materials in the presence of minute quantities of unwanted gaseous contaminates can destroy the integrity and shorten the life expectance of components.

It is natural to ask ourselves what can be done to further protect the work in a vacuum environment after the pumps have done their part in reducing the chamber pressure to as low as is economically feasible in a production environment? This task falls to getter materials. By Dan Herring