Gate-to-seat sealing surfaces are protected by tungsten carbide or chromium carbide HVOF coatings with hardness >1,100 HV and thickness 150–250 µm. These coatings resist erosion from produced sand and proppant during hydraulic fracturing operations. Post-coating lapping ensures flatness within 2 helium light bands and surface finish better than 0.2 µm Ra for optimal low-pressure seali... https://globalsealstech.com/product-category/oil-gas-seals/api-6a-gate-valve-seals/