Cutting tool insert cleaning and finishing by wet blasting

CVD (Chemical Vapour Deposition) coatings are applied at high temperatures and produce thicker, highly wear-resistant layers, making them well suited to high-speed steel cutting and roughing applications. PVD (Physical Vapour Deposition) coatings are applied at lower temperatures, preserve sharper edge geometries, and are generally preferred for finishing operations and materials prone to built-up edge. Neither is universally superior; the optimal choice depends on workpiece material, cutting speeds, and the specific insert geometry being used.

Insert grade determines how the carbide substrate responds to heat, abrasion, and impact during cutting. Finer grain grades offer greater hardness and wear resistance for finishing cuts, while coarser, more binder-rich grades provide toughness for interrupted cuts and roughing. Selecting the wrong grade for an application accelerates wear, increases chipping risk, and raises cost per part. Grade selection should account for workpiece material, chip load, cutting speed, and whether the operation is continuous or interrupted.

Premature chipping typically results from one or more of the following: an underprepared or overly sharp cutting edge that concentrates stress at the tip; incorrect grade selection for the level of impact in the cut; inadequate or incorrectly directed coolant causing thermal shock; excessive feed rates; or poor coating adhesion resulting from insufficient pre-coating surface preparation. Identifying the root cause requires examining the wear pattern on the failed insert, as chipping at the cutting edge presents differently from flaking caused by coating delamination.

Inserts should be stored in their original sealed packaging in a dry, temperature-stable environment away from direct sunlight and humidity fluctuations. Moisture exposure can initiate oxidation of the cobalt binder at the substrate surface, reducing coating adhesion when the insert is subsequently recoated or if it carries a pre-applied coating. Inserts should not be stored loose in bulk containers where contact between them can damage edge geometry. Stock rotation on a first-in, first-out basis is recommended for high-volume operations.

Yes, carbide inserts can be recoated, and doing so is common practice for reducing tooling costs in high-volume manufacturing. Before recoating, the existing coating must be fully stripped and the substrate surface re-prepared to remove oxidation, residual binder enrichment, and any surface damage from the previous cutting cycle. The substrate must be returned to a clean, reactive condition equivalent to that of a new insert before coating is reapplied. Incomplete preparation at this stage is one of the most common causes of reduced performance in recoated inserts compared to new ones.