Nitriding treatment improves surface performance of H13 hot work steel casting molds. Nitride‑layer thickness, surface hardness and brittleness jointly determine practical benefit for LPDC, gravity and CPC counter‑pressure casting mold.
Effective nitriding layer 0.08‑0.12 mm brings optimum comprehensive performance for aluminum casting environment. Layer thinner than 0.05 mm delivers limited anti‑erosion improvement; above 0.15 mm raises brittleness risk for LPDC casting mold gating inserts.
Surface hardness after qualified nitriding should reach HV 850‑1050. Hardness below HV800 indicates insufficient nitriding effect; H13 hot work steel surface still suffers fast aluminum‑alloy scouring in aluminum wheel gravity casting mold production.
Nitriding shall be executed after complete quenching‑and‑tempering heat‑treatment. Performing nitriding before tempering reduces overall mold service‑life by 40 %; residual stress triggers early crack for CPC counter‑pressure casting mold thin‑wall inserts.
Procast CAE simulation cannot directly calculate nitriding‑layer wear rate. Service‑life gain relies on practical statistical data; qualified nitriding extends gating insert service‑life by 38‑44 % under identical EV structural‑part mold working‑condition.
Over‑nitriding creates brittle compound layer. Brittle layer easily peels under thermal cycling; peeling fragments fall into cavity and generate embedded‑inclusion defects or secondary casting porosity defect inside aluminum alloy castings.
Local shielding is needed for thread holes and fitting‑mating faces. Unwanted nitriding on assembly surfaces increases fitting gap and jamming risk for combined multi‑insert LPDC casting mold assemblies.
Nitriding quality inspection requires cross‑section metallographic sample. Only surface‑hardness test cannot distinguish thin effective layer from brittle over‑nitrided layer for gravity casting mold critical wearing components.
After 1200‑1600 casting cycles, nitriding layer gradually wears away at high‑scour positions. Gating zone shows obvious wear earlier than cavity surface for CPC counter‑pressure casting mold aluminum alloy foundry mass‑production.
Re‑nitriding can be conducted after surface repair, yet every re‑nitriding amplifies internal residual stress. More than two re‑nitriding cycles raise thermal‑cracking probability of H13 hot work steel inserts by 31 %.
Nitriding cannot fix base‑material defects. If H13 substrate contains internal inclusions, nitriding only improves surface; substrate‑originated thermal cracks will still propagate for aluminum wheel LPDC casting mold under cyclic thermal load.
Procurement specification must define nitriding thickness range, surface‑hardness scope and forbidden over‑brittle compound‑layer. Ambiguous requirement leads to inconsistent nitriding quality on cross‑border procured EV structural‑part mold sets.
FAQ
Q: What target nitriding‑layer thickness for H13 aluminum casting mold components?
A: 0.08‑0.12 mm achieves balanced anti‑erosion and brittleness performance.
Q: What surface HV hardness target after qualified H13 nitriding treatment?
A: HV850‑1050; lower value means insufficient anti‑scour performance gain.
Q: When should nitriding treatment be arranged relative to heat‑treatment?
A: Must be finished after quenching‑tempering; before‑temper nitriding shortens life by 40 %.
Q: What risk is brought by over‑nitriding H13 mold steel inserts?
A: Brittle layer peeling may create inclusions or casting porosity defect on castings.
Q: How many re‑nitriding cycles are suggested for one H13 insert?
A: Avoid more than two re‑nitriding cycles; crack risk rises by 31 %.
Q: Can nitriding remedy internal base‑material defects of H13 hot work steel?
A: No, nitriding only modifies surface layer; substrate defects still propagate.
Q: How to reliably judge nitriding‑layer quality instead of only hardness test?
A: Metallographic cross‑section inspection evaluates real effective nitride‑layer status.
