Recent Trends and Developments in Vacuum Furnace Processing Technology for the Heat Treatment of Steel by David Pye

“Recent Trends and Developments in Vacuum Furnace Processing Technology for the Heat Treatment of Steel.

  • The future of metallurgical thermal processing technology is changing on almost a daily basis. This development has been necessitated towards clean critical heat treatment, as well as metallurgical thermal surface treatment developments.
  • Confidence by metallurgical processing engineers, heat treaters, manufacturers of furnace equipment, has grown in leaps and bounds during the past two or three decades.
  • Vacuum furnace technology has been known and used by engineering industrialists who have had the foresight to develop this process technology as the vehicle with the potential to accommodate many of the new thermal metallurgical transformation for many of today’s engineered and manufactured products.

What is the real impact of vacuum furnace technology and where is it heading?

Rapid and major industrial developments in conjunction with industrial science has helped many people in many countries to enjoy a better quality of life with new engineered products.

Sadly, there are three disturbing of interrelated tendencies that seem to arise in the wake of a major new technological development;

The technology often hovers in the background for many years before accomplishing any significant popularity both metallurgically and financially which would lead to more tangible benefits for the industries who require almost what can be said to be, ‘a perfect metallurgical transformation by the application of heat.

The Technology Paradox.

New metallurgical processing technologies seem to censor around a paradox. On the one hand, they are often welcomed as a more effective and efficient means to attain better metallurgical results and an enhanced quality of life yet on the other hand, the new technologies are very often resisted and decried.

Amid the rapid evolution of material science, one finds vacuum furnace technology that encountered such a similar fate. We find that on the one hand there are those who swear by it and who will invest every financial resource possible in that technology to make their operations more productive, quality oriented and obviously profitable.

Vacuum furnace technology has now achieved a tremendous potential to grow well into the future considering current and projected international trends. It is the technology that will help material science and their industrial associates to move comfortably into the third millennium but first there are problems to address.

The knowledge basis of vacuum processing technology is now becoming an accepted as a means to accomplish a thermal metallurgical transformation, on a repeated basis and very well controlled base process technology, which is to develop process technologies for processing thermal to thermally treat more complex metal alloys.

Vacuum thermal processing technology has an important role to play in the field of brazing of complex geometrical nonferrous alloys such as aluminum alloys.

Metallurgical Thermal Treatments Under Low Pressure Conditions.

Moving away from equipment and into process technologies, vacuum heat treatment has progressed dramatically from the simple annealing forward stress relieving processes to incorporate many various surface modification processes.

For example, the deposition of an exotic metal compound onto a metal substrate or the diffusion of gaseous elements into the surface of a metal or material composition.

Some of the thermal surface treatments that are currently being process utilizing  

low pressure conditions are;

  • Low-pressure carburizing. This now allows the metallurgist the ability to carburize at higher selected process temperatures for carburizing. The caution here is that the austenitizing of the carburized surface still follows the principles of careful temperature selection in order to transform the surface into a controlled martensitic form.
  • Low-pressure plasma carburizing. This procedure is still perhaps in its infancy and will most likely consume some time before it becomes a well-accepted and standard method of carburizing utilizing plasma. The unique feature of plasma carburizing is that the process gas consumption is now at a minimal utilization because the hydrocarbon process gas is only required at the surface of the component being carburized rather than necessitating the need to fill the process chamber with the hydrocarbon gas.
  • Plasma nitriding. Plasma nitriding is a low temperature process which utilizes either nitrogen-based gases such as ammonia or varying ratios of molecular nitrogen and molecular hydrogen and is now a proven and accepted method of nitriding.
  • Chemical vapor deposition. This procedure makes use of low pressure conditions to deposit to deposit onto the surface of a component, a high hardness, hard wearing metallic deposition such as titanium nitride, titanium and carbon nitride etc.
  • Physical vapor deposition. This procedure is particularly attractive because of its low operating temperature of approximately 1000°F (550°C) 

Not all of the processes mentioned require a high hardness or wear resistance, some components may call for a combination of wear and corrosion resistance.

Typical applications of these procedures are generally utilized for high wear conditions, and corrosive conditions. Components that are generally seen to be utilized by these processes are cutting tools, hydraulic equipment and components that are likely to be subjected to either high wear conditions, or corrosive conditions, or a combination of high wear and corrosion resistance.

What Has The Future In Store?

The future automobiles will more than likely feature high percentage of ceramics and or carbon reinforced carbon fibers. The basic automotive designs which would include resistance to abrasion (such as crankshafts, valves transmission products will remain the same but within a process of design even dilution based on marketing, costs safety factors.

Material compositions may shift radically in the very near future.

The commercial heat treater as well as the captive/in-house heat treater is finding it increasingly more difficult each day to;

  • Recruit specialized and knowledgeable personnel.
  • The process technology generally requires high capital investment.
  • Maintain and control the equipment both mechanically as well as electronically.
  • To achieve maximum equipment utilization to ensure a sound return on investment.
  • To provide personnel for quality assurance and examination of the metallurgical conditions achieved.

The Skills Challenge.

The world continues to face a serious skills shortage in critical technical fields and it is the writers prognosis that this plight will continue and may well even deteriorate if we as industrialists, technologists do not create enough synergy and force to help create an education and training revolution between now and the next millennium.

A basic school education and a little University or technique on education will no longer suffice. The next requirement will be the dire need for continuing education at virtually every level and in every sphere of industry.

It is the technician that is operating the heat treatment furnace and the process control of the desired metallurgy that can literally ‘make or break’ the component.

The writer strongly believes that the person on the shop floor is the person who needs to gain an understanding and a grasp of;

  • Material analysis.
  • Performance of materials.
  • An understanding of the process that has to be conducted and many other supportive disciplines necessary to ensure good quality metallurgical results.

This will require the development of an education and training system that will enable us to remain at the vanguard of technology, with confidence and competence. It will also have to make was more quality minded, productive, innovative and strategic in our thinking.

In addition to this we have to be more cost-conscious and entrepreneurial rather than making goes complacent enough to settle for the survival same that so often characterizes modern industry.

Good heat treatment makes the product, bad heat treatment breaks the product!!”