Properties evaluation of semi-crystalline and amorphous polymers injected in AISI P20 molds repaired by welding

Résumé

Injection molds can fail after a certain period of use, which may compromise the final part’s integrity and quality, but that can be solved using welding repair processes. This work aimed to investigate the influence of AISI P20 molds repaired by Gas Tungsten Arc Welding (GTAW) and Nd-YAG laser-welding processes on the properties of injection-molded parts with semi-crystalline (polypropylene) and amorphous (polycarbonate and acrylonitrile butadiene and styrene terpolymer) thermoplastics. Welds were prepared by machining 0.8 mm-deep 40 mm x 5 mm grooves to be filled by GTAW and Nd-YAG laser-welding deposits, in order to simulate the repair of AISI P20 molds. All polymers were injected into weld-repaired and unrepaired molds, and then evaluated in terms of microstructure, crystallinity degree, mechanical properties and gloss. The results suggest that the repaired region for both studied welding processes, despite the difference in hardness of the weld region, does not significantly affect the properties of semi-crystalline and amorphous injected polymers.

Keywords: molds, weld repair, polymers, injected parts, AISI P20.