The Instrumented Indentation Study of HVOF-Sprayed Hardmetal Coatings

Abstract

Elastic-plastic properties, namely, hardness and YoungÕs modulus, of four HVOF-sprayed hardmetal coatings were measured by instrumented indentation using Oliver-Pharr method Nanoindenter XP MTS with a continuous stiffness measurement (CSM) module. The results show that with sufficient number of CSM measurements, one can distinguish between indents made in the hard particles and indents made in the binder material. This can be accomplished by analyzing the plots of hardness and YoungÕs modulus versus load (or versus indentation depth). Further development of the dependence curves enables the load (or indentation depth) to be set to correspond to the point of transition from a single structure component to the composite material and to determine the properties of both. Comparison of results of CSM measurement with the results of single indentation measurement at a defined load reveals a new perspective on the origin of the indentation size effect in hardmetal coatings. The measurements show that the increase in both the hardness and YoungÕs modulus with decreasing load is caused mainly by the predominant influence of hard particles in the coatings.

Mechanical properties of WC coatings evaluated using instrumented indentation technique

“…The elastic moduli E c , which were computed following this methodology, exhibit the same trend reported in Table 2, when the computation is carried out employing equation (13), although their magnitude is somewhat less.…”

“…The ISE determined for contact depths of ,1?5 mm in the coatings is in agreement with the results reported previously by several authors in different materials deposited by HVOF thermal spraying. 12,13,16,32,33 La Barbera-Sosa et al 16,32 and Santana et al 12 have reported the occurrence of a marked ISE in both Ni and WC based coatings for indentation loads less than y2 N, equivalent to penetration depths in the range of approximately 1-2 mm. Such an effect is associated with the microstructure involved in the small indentation volume, as well as the occurrence of the coating microcracking.…”

“…The computation procedure first involved the fit of the unloading curve to equation (13), by imposing the following restrictions 0ƒhƒ1 ; E c w0 ; h min ƒh 0 ƒgh max (15) Particularly, the third restriction is associated with the possibility of the occurrence of piling-up (h 0 /h max .1) or sinking-in (h 0 /h min ,1). Here, h min and h max represent the minimum and maximum penetration depths during the unloading process.…”

Possibilities of Utilization Thermally Sprayed Coatings in the Field of Sink Rollers Renovation

“…4. Authors [13] visualized dependence of microstructure, properties and wear rate of the cermet coatings containing metallic binder phase in Fig. 10.…”

Measuring mechanical properties of plasma-sprayed alumina coatings by nanoindentation technique

“…Values obtained helped the study of splat boundaries, pores, oxides and microcracks present in the coating composite. 25 Afrasiabi The available literature provides ample insights to the methods of mechanical characterisation of bulk materials, thin films and functionally graded materials in terms of hardness and elastic modulus. Very few actually studied plasma-sprayed alumina coatings to evaluate elasto-plastic responses through indentation.…”