Evaluation of Kinetic and Thermal Sprayed Coatings for Protection of Die-Casting Moulds against Soldering and Erosion

Abstract

Soldering and Erosion are some of the biggest problems plaguing the die-casting industry. In an attempt to overcome these problems, candidate cermet coatings were developed by kinetic and thermal spray techniques (HVOF, APS). The porous MoB-based cermet powder feedstock (MoB/NiCr, MoB/CoCr) was deposited on grit-blasted plates and cylinders of AISI H13 (SKD61), a preferred die (mold) material. The coatings were characterized for their microstructural, chemical and mechanical properties. The durability of these coatings against soldering was investigated at lab-scale by immersing the coated cylindrical specimen in molten aluminium alloy (ADC-12) in an inert argon atmosphere for 25 hours at 670℃. The results showed that both MoB/NiCr and MoB/CoCr displayed high soldering resistance as negligible intermetallic formation occurred during the immersion test. This is attributed to the existence of multiple borides in the coatings. The coatings also displayed high mechanical properties. In particularly, kinetic sprayed MoB/NiCr showed higher bond strength, hardness, and wear resistance than MoB/CoCr. This suggests that MoB/NiCr will show higher durability than MoB/CoCr during high pressure die-casting of aluminium.