A tool surface is lubricated by high pressure blast spraying a powder lubricant comprising B nitride of particle size 0.6-1.5μ at a spray pressure of 4-5 bar, onto the tool surface. This produces a high temperature compacted coherent lubricant film on the surface while smoothing, strengthening and compressively stressing the tool surface. Preferably the powder lubricant comprises 95-5 wt. % B nitride and 5-95 wt. % boric acid or borosilicate glass. This process gives good wear resistance and good lubricity.
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