Hardening a "brush hog" mower blade to retain its strength and edge

A. Depending on the type of steel that the blade is made of, you may consider cryogenic treatment to extend the useful life of the blade. Cryogenic treatment of carbon steels has been shown to extend the operational life of cutting tools by as much as two to three times. After cryogenic treatment, the wear resistance of the steel is increased, thereby enhancing the tool's ability to retain a sharp edge. Deep cryogenic treatment, or cold treating, is similar to heat treating in that Time and Temperature produce Transformations in the steel. These include the formation of a uniform grain (or crystal) structure that eliminates voids and imperfections (of retained austenite) by creating a pure, homogenous crystal structure (of martensite). Additionally, the carbon structure is modified through the formation (or precipitation) of eta-carbides. Lastly, residual stresses, that propagate into cracks, are greatly reduced to eliminate many failures typically attributed as fatigue failures. I recommend that you give it try. Not only will the blades stay sharper longer, but because of the reduced sharpening required, they will have a longer functional life. The cost of cryogenic treatment usually is low enough to provide a fast payback, especially when you look at eliminating the down time and associated expense of re-sharpening, plus extended life of the tool.

A. I find that welds from a wire welder are very hard. You could run a large bead on the edge of the blade then grind it sharp but not let it get red hot. Quench it often as you grind. This results in a sharp edge of weld material. it seems to be much harder than just the steel itself. You can barely cut a saw blade but I have yet to see a hack saw blade that will cut a weld bead.