Considering Impact and Corrosion Resistance in the Performance of Heavy Wear Resistant Coatings
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https://doi.org/10.1007/s11837-020-04390-3 Ó 2020 The Minerals, Metals & Materials Society
SURFACE ENGINEERING: APPLICATIONS FOR ADVANCED MANUFACTURING
Considering Impact and Corrosion Resistance in the Performance of Heavy Wear Resistant Coatings CHRISTIANE SCHULZ and COLIN HALL1
¨ FER,2 JACOB PLOWMAN,1,3 ,1,4 THOMAS SCHLA
1.—University of South Australia, Adelaide, Australia. 2.—LaserBond Ltd, Sydney, Australia. 3.—University of Bath, Bath, UK. 4.—e-mail: [email protected]
Laser clad coatings consisting of a Ni-based matrix and tungsten carbide (WC) hard phases are used for heavy wear protection of components in many industries. Matrix composition and WC type can be chosen to give these composites resistance to erosive/abrasive wear, as well as to the impacts of particles and corrosion. Maintaining ductility in the matrix is important, so that it can absorb impact energy and minimize cracking, thus avoiding penetration of corrosive media through cracks and subsequent corrosion in the substrate-cladding interface. Claddings were tested for their impact resistance by means of a single impact with a hard, spherical indenter. The depth of impact craters was measured, and the cracking behavior was analyzed. Corrosion resistance of Ni/WC composites, a HVOF WC/CoCr coating and a hard chrome reference coating were tested by electrochemical corrosion in a 3.5 wt.% NaCl solution and by exposure for up to 1000 h in a salt spray test.
INTRODUCTION Parts in high-wearing applications such as pumps, pipes, and transport rolls for transporting slurry in mining and marine applications, and chisels, ploughs, and cutting blades in agriculture, require claddings to withstand impact loads and corrosion as well as typical abrasive or erosive wear.1–3 Currently, claddings are selected based on their performance in erosion, abrasion, and corrosion wear tests which are thought to be indicative of in-service performance. In these applications, however, claddings could be randomly impacted by rocks or other hard objects. They should, therefore, be designed to also protect against impact induced wear. Wet soil and slurries can have ions such as Cl dissolved in them, which induces an additional corrosive effect on claddings in these applications. Laser cladding is a build-up welding process utilizing a high-powered laser to melt a powder feedstock material directly onto a metal substrate. The laser beam is focused on the work piece where, due to absorption of the beam energy, the base (Received July 10, 2020; accepted September 14, 2020)
material is locally heated up to its melting temperature, creating a melt pool. The powder feedstock is injected into the melt pool to form a metallurgical bond with the substrate. Laser optics and powder nozzle are moved over the work piece to deposit a uniform coating or an additively manufactured 3D part.4 Claddings for high wear resistance with good corrosion resistance are often composed of a Nibased matrix with tungsten carbides as a hard phase.5 Such metal matrix composites (MMCs)
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