HRSA is the most difficult material to machine and the most expensive metal to buy. Due to the costly material and manufacturing costs, it is not as prevalent in machine shops as steel or aluminum, but it is a vital niche to grasp. The degree of machinability varies between 5% and 40%.

Heat-resistance Superalloys are a class of materials designed for extreme strength and corrosion resistance. Their alloys must also maintain these qualities at extremely high temperatures and in corrosive conditions. Jet engines, automobiles, oil & gas equipment, and medical implants are all examples of where they're used.

Working With Heat-Resistant Superalloys

In machining, super heat-resistant alloys (HRSAs) require a unique strategy. Cutting tool manufacturers have developed new and varied products and tactics to ensure dependable, effective, and inexpensive machining. The qualities that make these alloys appropriate for such applications also affect their machinability.

Achieving Success With the Difficult

Machinability refers to a metal's ability to respond to and react to machining.  The four primary elements determining machinability are the mechanical forces created during machining, chip formation and evacuation, heat generation and transmission, cutting tool wear, and failure.

HRSA and titanium alloys can be machinable with the same tools and processes as common steel and iron. Machinability concerns relate to tool life, process time, dependability, and component quality.

With the introduction of new cutting tools designed expressly for these high-performance metals, the general norm is to increase cut depths and feed rates. Fine-grained carbide grades that give good high-temperature edge strength, coating adhesion, and resistance to notching produced by work hardening are among the tools designed to manage these more demanding requirements. 

For roughing and polishing these high-performance alloys, ceramic and PCBN tools have been created.

Hard Facts

The machining of HRSA is also complicated by its proclivity for strain and precipitation hardening. For a finishing pass, a slightly deeper depth of cut places the sharpest section of the cutting edge below any strain or precipitation-hardened areas of the part.

On the other hand, a deep finishing pass can cause vibration and degrade the surface polish. Strain hardening occurs. Steel is more susceptible to strain hardening than nickel and titanium-based alloys. With either tendency, the material's structure may change dramatically after just one cutting tool run, requiring a second pass to cut through a much tougher surface. 

The answer is to reduce the number of passes. This method also necessitates a reassessment of the finishing process, which generally entails repeated passes at short depths of cut and slow feed rates.

A deeper cut positions the sharpest section for a finishing pass. Although HRSAs are not drastically different from tough irons or steels in terms of mechanical or force-related difficulties, there is one significant distinction – most notably in heat generation and dissipation.

Economic and Reliability Aspects

Increased depth of cut and feed rates help productivity when it comes to machining parameters. Although the rates used to machine nickel- and titanium-based alloys are still slower than those used to machine steels, current research focuses on developing cutting tool characteristics that will allow for even faster-cutting speeds while preserving useful tool life. 

Along with cutting tools, other parts of the metal cutting process, such as the use of a high-pressure direct coolant (HPDC) system, can boost productivity. Additionally, the cost has to be considered. Given the high cost of HRSA parts, the tool utilization index provides a more reliable indicator of production efficiency.

As is always the case, the key to maximizing the benefits of freshly discovered metal cutting technology is understanding how and when it should be used. SCTools' knowledge and experience make us a fantastic place to start to help you machine better! 

If you have any questions about carbide cutting tools, end mills, drills, etc. be sure to reach out to us @ sctools.co/Home or call us at (877)737-0987. We help you machine better!