Apollo-Shield is a collaborative effort between Alberta Industrial Heat Treatment and Apollo-Clad Laser Cladding. This new patent-pending technology has been developed to combine the best aspects of Carburizing, Nitriding, Laser Heat Treatment, and Induction Heat Treatment.
The process features:
– Surface hardness greater than or equal to that of carburizing
– Deep case depths of Induction Heat Treatment
– Low processing temperatures to limit distortion and maintain mechanical properties
– Broad alloy catalog for a wide range of alloys
– Ability to target specific features like Laser Heat Treatment to maximize value
– Overall case depth can be tailored to the application
– Hardness is consistently high throughout the case
– Case Hardening has no negative impacts on the base material
Apollo-Shield as a Disruptive Technology
One of the biggest challenges for design engineers is creating parts with good mechanical properties in the core with good wear properties at the surface. Carburizing is popular for its relatively deep case depths, but it requires the use of specific grades. Low carbon carburizing grade steels such as 8620 and 9310 alloys are expensive and have relatively low strength.
Alloy steel like 4330V can have double the yield strength of 8620 and is substantially cheaper but obtaining the hardness and case depth of carburization has been impossible until now.
Unlike carburizing, Apollo-Shield doesn’t require a quench, which minimizes distortion and maintains the final temper properties of the core material (suitable for finished parts).
Apollo-Shield is a selective heat treatment method capable of targeting specific features like the contact face of a gear tooth (shown above).
The Apollo-Shielded area can be as small as 4mm in width allowing for selective application as required by the design.
3 Distinct Regions of the Hardening Profile
The hardening profile for Apollo-Shield is unique in that it features 3 distinct regions which combine to create the ideal case hardening treatment:
1. Surface hardening on par with the hardest steels makes up the first 0.005-0.025”, which provides resistance to galling and abrasion while lowering the coefficient of friction.
2. Plateau of the fully hardened base material (~55-60HRC for alloy steels) whose depth can be adjusted to control the overall case depth. This improves the resistance to contact fatigue when compared to diffusion hardening methods like nitriding.
3. Abrupt return to base material hardness with minimal intercritical microstructures forming.
Apollo-Shield cases are metallurgically bonded to the base material and do not exhibit chipping or spalling tendencies despite their high hardness. This has been validated using Rotary Impact Testing which is commonly used to evaluate the bonding of corrosion-resistant overlays or hard facing. Specimens were subjected to 24 minutes of 8kJ impacts at a frequency of 150RPM (~3600 impacts). The Apollo-Shield specimen showed much greater resistance to smearing and indentation compared to deep case gas nitriding. The indentation depth was reduced by 40% compared to nitriding, while the mass loss remained negligible (0.001g).
Figure 2 Wear Scars for Nitrided (Left) and Apollo-Shield Rotary Impact Specimens (Right) demonstrate the improved resistance to impact. Depth of the nitrided wear scar was 0.013″ compared to 0.008″ with Apollo-Shield. Apollo-Shield also demonstrated minimal mass loss (0.001g).
Apollo-Shield compared to Nitriding
Apollo-Shield can replace almost any components which are currently being Nitrided, Carburized, Laser Heat Treated or Induction Heat Treated (bearing surfaces, mill gearing, rollers, crankshafts, camshafts, etc).