Burlington, Ontario, September 14, 2015 – VAC AERO has sold a VAV5448 HV-2 vacuum furnace to major manufacturer of components for the aerospace industry. The vertical, bottom-loading furnace utilizes 2-bar gas quenching and features a 54” diameter x 48” high graphite hot zone with a 2500 lbs load capacity. This is the first VAC AERO furnace in this facility used to increase the customer’s heat-treating capacity to meet the high demand for heat-treated work.

The furnace, which is capable of meeting applicable AMS 2750E requirements, is equipped with VAC AERO’s advanced Honeywell HC900 interactive hybrid control package with SCADA complete network integration capabilities and remote monitoring and control. VAC AERO’s decades of experience operating aerospace heat treating facilities allows them to provide turnkey customer solutions such as training, technology transfer as well as hands-on instruction and collaboration.

For many years, ASTM E384 has stated that test forces from 1 to 1000 gf can be used to determine the Vickers or Knoop micro-indentation hardness. But, is it realistic to consider using very low test forces when the indents are measured with a light optical microscope? ASTM E92 is being resurrected and changed to cover all test loads, micro- and macro-loads, from 1 gf to 120,000 gf. Most micro-indentation hardness testers manufactured over the last 50 years or more have provided the user with a 10X objective used to find the area of interest for testing and one measurement objective, 40X magnification being the most common. A few testers have offered 50X or 60X objectives to measure the indents. It is rare to find a tester with a multiple objective (and indenter) turret, such as the DuraScan system which has ports for 2 indenters and 4 objectives. But, even with the highest quality 100X objective, indents smaller than ~15 μm in length cannot be measured with adequate precision for realistic work. The ASTM standards should eliminate recommendation of use of test loads <50 gf for Vickers and <20 gf for Knoop.

In both ASTM E384 (Micro-indentation Hardness Test Standard) and the proposed revision and re-instatement of E92 (to cover both Macro- and Micro-Loads for Vickers and Knoop), test forces below 25 gf for both Vickers and Knoop testing are listed as permissible for use. The proposed E92 lists test forces for Vickers macro-testing up to 120 kgf , although no machine built in some time has provided forces above 50 kg. The original Vickers testers made in England did use test forces up to 120 kgf, but that is a historical fact, irrelevant today. By George Vander Voort

When performing any type of vacuum heat treatment it is always important to be aware of the possibility of evaporation and/or sublimation of elements, which can be present in the material being processed, introduced into the vacuum system with the workload, inherent in the equipment design or introduced during maintenance, repair or rebuilds. In cases where evaporation may be a concern, the vaporization rate is of prime importance and is directly related to the furnace pressure (the higher the pressure, the more frequent the collision of gas molecules and correspondingly, the few metal atoms leave the metal’s surface).

What is Evaporation? Vaporization is the process that occurs when a chemical or element is converted from a liquid (or a solid) to a gas. When a liquid is converted to a gas, the process is called evaporation or boiling; when a solid is converted to a gas, the process is called sublimation. The pressure exerted by the vapor of a liquid in a confined space is called its vapor pressure. As the temperature increases so too does its vapor pressure. Conversely, the vapor pressure decreases as the temperature decreases. By Dan Herring

To successfully process component parts in a vacuum furnace, we need to create and control the “atmosphere” surrounding the work. In general, applications run in vacuum furnaces can be broken down into five main (5) categories: Processes that can be done in no other way than in vacuum; processes that can be done better in vacuum from a metallurgical standpoint; processes that can be done better in vacuum from an economic viewpoint; processes that can be done better in vacuum from a surface finish perspective and process that can be done better in vacuum from an environmental perspective.

A principal difference between vacuum heat treatment and all other forms of thermal processing is the absence of, or perhaps better stated, the precise control of surface reactions. In addition, vacuum processing can remove contaminants, and under certain circumstances degas or convert oxides found on the surface of a material. Typical vacuum applications include industrial, food and packaging, coatings, analytical and medical technology, solar, semiconductor technology and research and development. In the heat-treating industry typical processes involve: Brazing, Hardening, Annealing, Case Hardening (e.g. carburizing, nitriding), Sintering, Tempering and Special Processes (e.g. degassing, diffusion bonding). By Dan Herring 

The Control Chart method described in ASTM E2554, and discussed by Neil Ullman, is an ideal procedure for evaluating the performance of hardness testers as it will detect any abnormalities that may occur with usage time. The control chart concept was first developed by Walter Shewhart in 1931 to define the state of statistical control and to detect random or special problems. In 1933, ASTM Committee E1 produced STP 15, “ASTM Manual on Presentation of Data.” This was supplemented in 1935 with “Presentation ± Limits of Uncertainty of an Observed Average,” the first use of the term “uncertainty” in statistical analysis of test data. Today, additional information on control charts is provided by E2587. By George Vander Voort

Image caption: Microstructure of wrought 7-Mo Plus duplex stainless steel (Fe – <0.03% C – 27.5% Cr – 4.2% Ni – 1.75% Mo – 0.25% N) electrolytically etched with aqueous 20% NaOH (3 V dc, 5 s) to color the ferrite blue. There is some light yellow-tan coloring of the austenite. The average Knoop hardness of the austenite was 361.8 HK and that of the ferrite was 263.5 HK.  Magnification bar is 20 µm in length. 7-Mo Plus is a registered trademark of Carpenter Technology Corp., Reading, Pennsylvania.

Vacuum deposition is a generic term used to describe a type of surface engineering treatment used to deposit layers of material onto a substrate. The types of coatings include metals (e.g., cadmium, chromium, copper, nickel, titanium) and nonmetals (e.g., ceramic matrix composites of carbon/carbon, carbon/silicon carbide, etc.), deposited in thin layers (i.e. atom by atom or molecule by molecule) on the surface.

Vapor deposition technologies include processes that put materials into a vapor state via condensation, chemical reaction, or conversion. When the vapor phase is produced by condensation from a liquid or solid source, the process is called physical vapor deposition (PVD). When produced from a chemical reaction, the process is known as chemical vapor deposition (CVD). These processes are typically conducted in a vacuum environment with or without the use of plasma (i.e., ionized gas from which particles can be extracted), which adds kinetic energy to the surface (rather than thermal energy) and allows for reduced processing temperature. By Dan Herring

This is the first in a new series of articles to be entitled “Practical Vacuum Pump Practice with Dan Herring.”

Burlington, Ontario, August 17, 2015 – A new column, written by vacuum heat treating expert Dan Herring “The Heat Treat Doctor”® in collaboration with Edwards Vacuum will be published monthly and offer helpful tips and techniques on vacuum pumping systems to a worldwide audience of individuals using all types of vacuum equipment. The first article will appear in the September 15th “What’s Hot!” newsletter. This VAC AERO exclusive publication launched  back in September 2007 and contains hundreds of archived articles can now be found in the “Resources” section of the VAC AERO website where anyone can sign up for the monthly newsletter.

The purpose of this column is to inform, educate and answer questions for anyone who owns and operates vacuum equipment or is thinking of doing so, focusing on commercial and captive heat treaters; engineers, metallurgists, maintenance personnel, supervisory staff, heat treat operators, quality control and quality assurance personnel, and anyone else who is interested in the subject of vacuum pumping and vacuum processing. Dan will draw upon his vast experience as well as work with leading Edwards’ experts in the field of vacuum technology to provide examples of the concepts being discussed.

Keeping pace with the development of new vacuum processing technologies is the reason VAC AERO takes pride in its continued support of the metal treating community by helping to promote, collaborate and assist others in their search for solutions on important issues in the practice and application of vacuum processing. The aim of this column as well as the three others is to continue to provide our readers with important and relevant knowledge-based articles and information that they are constantly seeking.

All brazed joints should be inspected after brazing to verify that the parts being brazed will be acceptable to the end-use customer. If the brazed-assemblies are complex, then 100% of the assemblies should be inspected to verify that the parts have been brazed properly and will meet end-use requirements.

This may include visual inspection of the exterior of all surfaces that have been brazed, and it may also involve one or more non-destructive testing (NDT) procedures to verify that each assembly will properly handle the end-use service conditions to which it will be subjected, such as fluid pressure, thermal cycling, or mechanical shock. Sometimes some destructive testing (DT) procedures are mandated, via an appropriate sampling plan, in order to physically examine the internal structure of some of the brazed joints. Is there any danger in using the examination of the cross-sectional microstructure of a brazed joint as an accept/reject criterion for the brazed tubular assembly? Yes, there is! Let’s see why……by Dan Kay