Why Badger uses Lambda X-Ray Diffraction measurements?

Other companies that say they do the same process that Badger Metal does should be questioned regarding their proof of this claim.  The only proven way to validate their declaration is by generating exacting curves using the below established procedures.  Anything short of this is simply a hit and miss attempt at doing MetaLLife and trying to accomplish what Badger Metal has developed and successfully been doing to all types of tool steels since 1983. 

MetaLLife processing is monitored on a production basis by using Almen intensity strips.  These strips are placed in strategic locations on the die or perishable tooling being processed.  The Almen strip will bend when processed and by measuring the height of the center curvature, the approximate amount of induced surface compression can be determined. Various strip thickness are used dependent on the intensity of the process.  i.e. For example, a T-21 process would use a thinner Almen strip than a more aggressive T-41H.  

While the Almen strip method is useful, it only provides a relative basis for measuring surface induced compression.  Surface compression is important, but the depth and shape of the curve is what ultimately determines how well the process variables are being applied.  The only accurate means for determining this residual stress distribution, is by measuring the surface and subsurface distribution of the compression.

X-ray diffraction (XRD) is the most accurate and proven method of quantifying the subsurface residual stress distributions that develop during MetaLLife or other mechanical compression processing.  These XRD methods use known  standards established by ASTM and SAE associations.  Prior to taking these measurements exacting criteria and specifications for processing methods have to be established and implemented.  These specifications are applied to multiple coupon samples which are then used in the XRD measurement phase.

Subsurface readings are then determined by successive combination measurements using x-ray diffraction instruments and then electro-polishing the surface to remove layers of material.  Electro-polishing removes material without inducing or changing the residual stress values.  This method is costly  and destructive in nature so it often skipped by other competitive companies because it involves the removal of the specimen coupon from the diffractometer each time to perform the electro-polishing.  This increases the amount of time required to take the readings which is very labor intensive.

Lambda has the capability of quantifying residual stress distribution using their unique automated StressPro_TM  apparatus.  The _TM allows the residual stress in one coupon specimen to be measured while layers of material are being electrochemically removed from another specimen.  The _TM then measures the resulting layer's residual stress which are defined in a computer file.  All the data obtained is properly corrected based on the penetration of the X-ray beam and the amount of layer removal.  By connecting the resulting data points it is possible to accurately draw curves showing both surface and subsurface compressive residual stresses.

Since the coupons we use for this testing are manufactured to exacting tool steel specifications and then processed using our highly defined and controlled criteria for each MetaLLife process, we and our customers are assured of optimum and repeatable values of compression (KSI) that are produced during the MetaLLife processing.