High-speed laser cladding: new developments for wear and corrosion protection

Abstract

Fusion-bonded and low-diluted overlay welded coatings are frequently very thick (>1mm), which results in high material consumption (kg/m2) and expenses. High-speed laser cladding is a novel process, which can produce thin fusion-bonded and low-diluted coatings with high coverage rates and low heat input. Coating materials utilized in high-speed cladding have varied from soft Ni-based superalloys to harder martensitic stainless steels and base materials from low alloy steels to austenitic stainless steels. The ultimate objective has been to develop crack-free alternatives to environmentally hazardous hard-chrome plating. In this paper, high-speed laser cladding was used to fabricate relatively thin Ni-based coatings on various cast irons for corrosion protection and Ni-based hard-faced coatings reinforced with chromium (Cr3C2) and tungsten carbides (WC/W2C), for the first time, onto low-alloy structural and quenched & tempered steels for wear applications. Obtained coatings were characterized with X-ray diffraction (XRD), optical (OM), and scanning electron microscopy (SEM). Corrosion performances were explored in long-term salt spray tests. Mechanical and wear properties were tested with Vickers microhardness measurements and three-body dry-sand rubber wheel abrasion tests (RWAT). It was shown that soft low-diluted Ni-based coatings protected the cast iron base materials in salt spray tests. Ni-based hard-faced coatings with hardness up to 1200 HV1 exhibited high wear resistance in low-stress three-body abrasion better than hard-chrome plated coating, which was attributed to the high volume fraction of hard carbide reinforcements.