Note:  This page contains CONFIDENTIAL INFORMATION of Apollo-Clad Laser Cladding, a Division of Apollo Machine & Welding Ltd., and is for the exclusive use of the intended recipients.  No part of this report is to be copied or distributed in any manner to anyone without the prior written authorization of Apollo Machine & Welding Ltd.

apollo shield logo

Hybrid Process for Enhanced Surface Hardening
United States Patent Application No.16/507,285
Filed July 10, 2019
Apollo Machine & Welding Ltd.

Hybrid Process for Enhanced Surface Hardening
Canadian Patent Application No. 3,044,930
Filed May 31, 2019
Apollo Machine & Welding Ltd.

Double arrow pointing down

About Apollo-ShieldTM

Apollo-ShieldTM 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 on par with induction heat treatment
– Low processing temperatures to limit distortion and maintain mechanical properties
– Broad alloy catalog with up to 4mm precision
– 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-ShieldTM 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-ShieldTM doesn’t require a quench, which minimizes distortion and maintains the final temper properties of the core material (suitable for finished parts).

gear tooth showing post apollo shield treating
Figure 1 Gear Tooth Selectively Hardened on contact face using Apollo-Shield

Apollo-ShieldTM 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-ShieldTM 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 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.
chart showing effect of the apollo shield treating
3 regions effected

Apollo-ShieldTM 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-ShieldTM 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).

Double arrow pointing down
nitrided metal vs not

Apollo-ShieldTM compared to Nitriding

Deep case depths on par with induction heat treatment”

Relative Wear Performance

Fig. 1. Wear Loss Relative to untreated AISI 4145 material. Apollo-SHIELD hardened 4145 Demonstrates a 260% improvement over untreated material, and a 185% improvement over nitrided 4145 as measured with Pin-On_-Disc Testing.


Apollo-ShieldTM can replace almost any components which are currently being Nitrided, Carburized, Laser Heat Treated or Induction Heat Treated.

Common applications include: bearing surfaces, mill gearing, rollers, crankshafts, camshafts, etc.

Want to learn more?

View the Apollo-Shield Datasheet HERE