Unprecedented Galling Resistance Of 316L After Expanite Surface Hardening!
Galling on stainless steel
Galling, or adhesive wear, is a pervasive problem for stainless steels, of which the soft 300 series are notoriously prone. In an on-going effort to increase its database of engineering data, Expanite recently conducted the ASTM G98 Standard Test Method for Galling Resistance of Materials on AISI 316L, with and without Expanite surface treatment. The results were remarkable, and challenge the conventional wisdom that a 'hardness differential' in a material couple is required to resist galling.
ASTM G98 test
The test geometry involves a cylindrical button which is rotated 360° against a stationary block under increasing normal force. After rotation, the contact surfaces are visually inspected for galling, defined in the standard as "a severe form of wear characterized by localized, macroscopic material transfer, removal or formation of surface protrusions when two solid surfaces experience relative sliding under load". The load is gradually increased until galling is observed, thereby establishing the threshold galling stress. The table below lists the extent of galling observed with increasing load.
Results with Expanite
The patented process that produced such results is known as Expanite. With Expanite, it’s possible to increase the surface hardness of stainless steels by up to 10 times, while maintaining or even enhancing corrosion resistance. This method is considered unique
since it’s suitable for austenitic-, ferritic-, martensitic and duplex stainless steels. Parts can be treated with extremely short lead times—a few days—which is previously unseen within surface hardening of stainless steel..