EXPERT RESPONSE PROVIDED BY GUILLERMO E. MORALESESPEJEL.
In general, many of the mechanical components in the power transmission
industry are suffering from harsher tribological conditions, e.g.—rolling
bearings and gears need to take/withstand higher power density, higher temperatures,
dynamic loads, particle contamination and thinner or insufficient
lubricant film. This follows the trend of the current economic constraints and
tighter environmental policies. It is common now to see engineers struggling to
design power transmission devices that consume less energy, last reliably longer
and waste no lubricant. Hybrid contacts (silicone nitride with steel) are excellent
solutions in these conditions—in particular, rolling bearings can take advantage
of this because they are historically (for the past several decades) manufactured
in a reliable way. Costs are also going down, as manufacturing techniques and
materials are improved. Bearing life can now be estimated for those hybrid bearings,
i.e.—SKF GBLM.
However, today’s high speeds or/and high accelerations impose high heat inputs
on surfaces, which might lead to adhesive wear and seizure. For that, coatings
like special DLCs—that feature wear-resistant, metal-containing hydrogenated
amorphous carbon coatings that are applied to the rolling element
surfaces—are a good solution. Alternatives that can work well, depending on
the conditions, would be black oxide and manganese phosphate coatings. If no
coating is used, then steels with high thermal conductivity are preferred, as they
can evacuate the heat at the surface in a fast and efficient way. Metal powder
technology also offers good solutions here.