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Zhuzhou Hetang cemented carbides

PCB microdrills, turning inserts and mining buttons fail at very different scales even when all use cemented carbide. Hetang is understood by tracing powder, sintering and edge records back to a specific failure.

Formation and regional foundations

Tungsten-cobalt feed and ultrafine powders establish chemistry, milling and granulation form the compact, sintering controls pores and binder, and grinding, coating and edge treatment create usable tools or wear parts.

A broken PCB microdrill, crater wear on a turning insert and a fractured mining button leave different surfaces. Matching each part to mixture, sintering, grinding and coating records reveals the material and process divisions in Hetang.

Core geography: A Hetang manufacturing area linking tungsten-cobalt powders, mixtures, pressing and sintering, precision grinding and wear applications

Material loop from tungsten-cobalt powder to three failure surfaces

Which process first left the clue behind this chip

Three tool families return from distinct failure surfaces to powder and furnace evidence; they share a material diagnosis, not one identical route.

  • Tungsten-cobalt powder sample — The powder sample covers tungsten, cobalt, carbon, oxygen and the particle-size tail, isolating sparse coarse particles or impurities instead of hiding them in a mean diameter.
  • Milled mixture and spray granules — Milling time, ball-to-powder ratio and slurry solids remain with the spray lot, while granule sections show whether binder segregation began before drying.
  • Microdrill rod and fracture section — Microdrills are sampled by rod position and their fracture faces are read beside edge damage, keeping micropores and concentricity error from disappearing in whole-rod strength.
  • Turning-insert edge and wear land — Turning inserts retain speed, feed, workpiece material and edge position, while crater wear, built-up edge and chipping receive separate counts.
  • Mining-button wear and fracture face — Mining buttons return with bit position, formation and drilled metres; mounting orientation reconstructs the impact path behind face crushing or side chipping.
  • Sintered carbide section — A sintered section returns pores, abnormal phases and cobalt distribution to the powder lot and furnace position, providing a common comparison point for damage from all three tool families.

01 · Powder purity sets the first defect

Oxygen, carbon and impurities alter later phases.

Powder receipt checks more than elements; agglomeration, oxygen and cross-lot mixing risk also matter. Incoming inspection places tungsten, cobalt and critical impurity chemistry beside particle size, agglomeration and oxygen for one lot, with samples taken from several package positions. Retained feed remains available until the related furnace runs are complete, allowing a sintering exception to return to the actual supplier lot. Package positions remain separate rather than merging an abnormal subsample into an average.

Sintering shrinks the compact and closes some pores, but it cannot remove feed impurities, oxides, or brittle phases created by carbon imbalance. A finished part may pass average hardness while a small contaminated region remains hidden in the narrow section of a microdrill or insert edge until load causes fracture. Feed sampling therefore retains package position and blend lot so abnormal chemistry near the break can return to the actual incoming material.

Retain each supplier lot and retest feed when a furnace exception appears rather than inspecting only finished carbide. Each supplier lot is retained separately, with opening, mixing and equipment-cleaning order recorded. When a furnace shows abnormal porosity, magnetism or phases, the laboratory retests feed and same-lot mixture and compares an adjacent normal run before assigning feed responsibility from the finished carbide alone. A neighbouring normal run separates feed variation from furnace drift.

  • Two powders with the same mean size can deliver very different edge life when their coarse tails differ.

02 · Milling and granulation redistribute binder

Uniform mixing is not a colour judgement.

Ball-to-powder ratio, time, medium and drying alter fracture, contamination and granule flow. Milling records ball-to-powder ratio, medium, time, temperature and contamination control, while spray granulation retains inlet and outlet temperature, granule moisture and screening. One mixture identity spans both operations so later green density returns to a particular machine and cleaning state. Granule moisture and flow remain linked through pressing.

Poor granule flow creates uneven green density and local weak zones in edges or slender rods. Uniform colour does not prove even binder distribution, and excessive milling can introduce contamination or shift particle size. Poor granule flow fills die positions unevenly. Slender rods and sharp edges expose those local density differences more readily because their sections are small. Uneven die filling grows through sintering shrinkage into local microstructural difference.

Match mixture samples to green-density maps and record equipment cleaning and lot changeover. Samples are taken at several points in the mixing tank and spray run for size, bulk density and flow, then matched to a green-density map. After a recipe change or equipment cleaning, a short lot confirms stability across die zones before continuous pressing, and abnormal granules are not blended into the next lot. Production expands only after the short lot passes, with abnormal oversize retained.

  • Uniform-looking spray granules do not prove an even binder distribution in section.

03 · PCB microdrills expose the smallest edge

The smaller the diameter, the harder it is for averages to hide local pores.

Microdrill blanks are sensitive to fine-grain uniformity, straightness and grinding damage, and fracture position is recorded. Microdrill rods are filed by diameter, straightness, concentricity and material lot, with enlarged images of the ground edge and fracture position. Trial drilling fixes board, stack, speed and feed so breakage life and hole-wall quality can be compared under one condition set. Break position and hole sequence show whether failures cluster near end of life.

High hardness with abnormal coarse grains or surface cracks allows drilling vibration to grow a small flaw rapidly. As diameter falls, one pore, coarse grain or grinding microcrack occupies a larger share of the section, which average hardness cannot describe. Fractures starting repeatedly at the same edge position suggest geometry or grinding damage, while scattered sections direct attention to material uniformity. Repeatability of fracture origin is closer to manufacturing cause than one bulk strength.

Trial drills are removed at fixed hole counts for edge wear, concentricity, and hole-wall burr checks instead of being observed only after all have broken. An abnormal microdrill retains board position and fracture direction for comparison with unused rod, and material or grinding changes repeat on the same board and hole sequence. Longer life is not an improvement when hole-wall quality falls, so the two outcomes remain side by side.

  • A microdrill fracture belongs to its rod position and cannot represent the entire rod.

04 · Turning inserts balance heat and friction

Crater wear, built-up edge and chipping are different mechanisms.

Insert inspection separates rake face, flank and edge and records speed, feed, depth and coolant. Turning trials bind work material, hardness, speed, feed, depth, coolant and cutting time to an identified insert edge. Crater wear, flank land, built-up edge and microchipping are measured separately rather than collapsed into one wear number. Wear morphology and cutting force reveal the cost of edge honing.

Coating heat resistance, substrate toughness and edge hone determine tool life together. A larger hone may reduce early chipping but raise cutting force, while a heat-resistant coating cannot compensate for a substrate crack. Comparing grades without work material, feed, speed and coolant turns different wear mechanisms into a misleading ranking. A trial must define failure first and then record wear location, parts cut and dimensional drift to show whether a change extended stable cutting or merely postponed another failure mode.

Use stepped cutting trials and sample at fixed wear rather than waiting for catastrophic failure. A stepped trial samples at preset flank-land widths and cutting times, retaining edge images, cutting force and surface quality. Formula, coating or edge treatment changes one item at a time and repeats on the same work material and coolant. Catastrophically failed inserts are archived separately. Each sampling point retains an insert that is not cut further for later review.

  • Insert wear morphology points to material or duty only when workpiece and cutting settings accompany it.

05 · Mining buttons absorb repeated impact

Rock and drill posture change impact direction.

Mining buttons face rock impact and abrasive cutting together; field returns retain hole position and orientation. Returned mining buttons retain bit position, orientation, drilled metres, formation and rig settings, while flattening, spalling and fracture are counted separately. An unfailed button from the same position serves as a control so the normal wear background is not lost by collecting only the worst fragment. A normal button from the same position provides a reference control for side load and material.

Static transverse strength cannot reproduce side load, repeated impact, and abrasive cutting together, while an abrupt formation change can redirect force instantly. Early fracture concentrated in several holes on one side points first to bit posture, assembly, and chip removal; random positions make material or sintering lot more suspect. Returned parts retain their hole-position distribution rather than being collapsed into one failure rate.

Compare wear by formation and drilled metres and separate normal flattening from early fracture. A set of buttons is recovered at fixed drilling distances in a comparable formation for mass loss, profile and fracture comparison. Laboratory reproduction combines impact and abrasion rather than using one crushing load. After a material change, bit design and operating conditions stay fixed across at least two recovery points. Rig and operating settings remain stable between the two recoveries.

  • Button position and orientation determine whether the dominant load is face crushing or lateral impact.

06 · The sintering lot explains pores and phases

Temperature profile and furnace position both matter.

Sintering records loading position, temperature, atmosphere and hold so shrinkage corresponds to microstructure. The furnace file retains loading layer, compact position, temperature and atmosphere traces, then maps shrinkage, porosity, magnetic and metallographic results back onto the load plan. The same formula may experience different thermal histories at edge, centre, upper or lower positions, which average furnace temperature cannot replace. The load plan becomes both production record and coordinate for spatial microstructure.

Load edges can develop decarburisation, carburisation, or binder migration that affects few pieces yet becomes an edge-chipping origin after finish grinding. Mixing furnace positions into average hardness removes the microstructural gradient and can wrongly blame coating or grinding. Sintering inspection retains centre, edge, upper, and lower positions and maps abnormal structure to the finished part’s original location in the load.

Sample multiple furnace positions and map microscopy, magnetic and dimensional data onto one loading plan. Representative positions in every run retain sections for common porosity, magnetic, dimensional and phase checks. An abnormal zone is compared with neighbouring positions before temperature and atmosphere are reviewed. After changing loading or profile, the formula stays fixed and spatial convergence matters more than one best specimen. A change is effective for the run only after spatial results converge.

  • Beyond the furnace trace, tray position is an essential coordinate for explaining sintering variation.

07 · Grinding and coating cannot hide substrate faults

Final processes can create cracks and residual stress.

Grinding burn, microchipping and coating adhesion are observed on the same edge section. Matched edges from before grinding, after grinding and after coating retain edge radius, burn, microchips, residual stress and coating adhesion. Section identity remains tied to the original furnace run so damage created in finishing can be separated from a pre-existing substrate defect. All three states use one orientation and magnification for continuous damage tracking.

Once a wear-resistant coating covers the substrate, an existing microcrack remains and an early chip may be hidden by colour and film, while grinding heat can initiate a new crack in otherwise sound material. A final visual inspection alone collapses substrate weakness, grinding burn, and interface delamination into vague labels such as chipping or coating loss. Following the fracture inward and recording origin, heat tint, and film boundary separates the three routes.

Retain controls before and after coating and measure edge radius, surface damage and residual stress change. The same edge is imaged and measured in three states. A grinding change is assessed on an uncoated item, while a coating change uses the same substrate. After failure, a section follows the crack inward and combines residual stress with interface evidence rather than assigning cause from surface colour. Sections and stress evidence decide the cause, not coating colour or appearance.

  • A crack introduced during grinding will not disappear through a change in sintering settings.

08 · Failure files return to a repeatable duty

An image matters only with workpiece and conditions.

A failure file includes product position, work material, conditions, lot, furnace and finishing history. A failure package contains more than one fracture image: product position, workpiece or formation, operating conditions, material lot, furnace run, grinding and coating all accompany it. Fragment, unused control and normal same-lot item are retained separately with consistent scale and orientation in images. Complete history keeps every fragment tied to product, duty and manufacturing path.

If firms exchange conclusions without original sections and conditions, powder, tool and user teams build different stories. A section without its duty shows how it broke but not why it broke then. Powder, sintering, toolmaking and user teams can build incompatible stories from summaries. Shared physical evidence and operating conditions allow competing explanations to be removed. Shared physical evidence makes parties test one hypothesis rather than exchange unrelated summaries.

Select the shortest shared reproduction duty and observe the same failure measure after changing one variable. The parties choose the shortest safe reproduction duty, fixing work material, speed, load and cooling while changing one candidate factor. The same morphology measure is observed before and after and returned to the original failure file. If failure type changes, that trial cannot close the original issue. If reproduction creates another fracture, the duty is redesigned rather than treating resemblance as identity.

  • Diagnosis gains a control only when the failed tool, a normal peer at the same position and the original duty all return together.

Sources and reading notes

Grade name, hardness and transverse rupture strength are only a start. Assessment separates edge scale, impact, temperature and abrasion by product and does not transfer laboratory coupons directly into tool life.

  • Zhuzhou Hetang cemented carbides: National recognition year is 2024.
  • Zhuzhou Hetang cemented carbides: List validity is 3 years.
  • Year of the provincial process report: 2024.
  • Typical failure products examined: 3 product types.

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Sources

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