Dry Sliding Wear of Laser-Clad High-Vanadium Crucible Powder Metallurgy (CPM) 3V, 9V, and 15V Tool Steel Coatings

Abstract

Dry sliding wear of laser-clad high-vanadium Crucible Powder Metallurgy (CPM) 3V, 9V, and 15V tool steel coatings was investigated in “as-clad” and “heat-treated” conditions against cemented WC-6%Co ball, where a hardened wrought AISI H13 hot-work tool steel substrate was used as a baseline for comparison. The 15V coating demonstrated a superior sliding wear resistance; the 9V coating possessed a better sliding wear resistance than the 3V coating, but was inferior to the 15V coating, and all the laser-clad CPM coatings showed a better sliding wear resistance than the hardened H13 substrate. The sliding wear resistances of the 3V and 15V coatings were further improved after double tempering at 540 and 550 °C (corresponding to their respective “secondary hardening”), respectively. By contrast, the sliding wear resistance of the 9V coating after double tempering at 550 °C (beyond its “secondary hardening” temperature) was slightly dropped instead, ascribed to the reduced hardness. The microstructures of the coatings, the morphologies, and chemical compositions of the worn surfaces were studied, revealing that the adhesion and oxidation played important roles in the dry sliding wear, depending upon the hardness of the martensitic matrices of the coatings and the morphologies and amount of (V, Cr)8C7 vanadium carbides dispersed on the matrices.