On propose une nouvelle methode de caracterisation tres precise des materiaux. On mesure les caracteristiques de propagation des ondes de fuite a la limite entre l'eau et l'echantillon; la vitesse de phase et l'attenuation sont determinees a travers des mesures de la courbe V(z). On presente une methode d'analyse spectrale pour obtenir les proprietes acoustiques a partir des courbes V(z). Description des mesures effectuees en utilisant des materiaux isotropes ou anisotropes pour lesquels les vitesses s'etendent de 2000 a 11000 m/s. On examine tous les modes d'ondes de fuite impliques dans les phenomenes d'interferences dans les courbes V(z). Resultats experimentaux confirmant les resultats theoriques. Application a l'analyse de la structure des materiaux polycristallins

Material Characterization by Line-Focus-Beam Acoustic Microscope

Abstmct-The ability to measure elastic properties of materials and layered structures nondestructively on a microscopic scale gives rise to a new field of metrology via the reflection acoustic microscope. Acoustic micro-metrology accomplishes this task via the acoustic material signature (AMS), which is obtained from planar and curved surface specimens alike. The AMS constitutes a unique function that arises from interference of elastic propagating modes. These are simultaneously and coherently excited in the wide-angle lens ensembles that distinguish the acoustic microscope from other forms of ultrasonic pulse-echo systems. Several potential applications taken from diverse fields are described with experimental case studies. Examples of both materials and layered structures are described. Distinguishing features of different crystal orientations of single crystals may be readily detected. It is shown that the film thickness measurement of a wide variety of opaque materials is readily accomplished nondestructively and without a step. Machining damage in a Be surface may also be determined nondestructively. The AMS limitations imposed by frequency and material combinations, as presently viewed, are treated in the concluding section.

Acoustic Micro-Metrology

Tribochemical wear of silicon nitride in water, n-alcohols and their mixtures

Mechanical properties of ceramic surfaces such as hard- ness, indentation fracture toughness, and wear resistance are largely influenced by the behavior of small flaws and defects, such as micro- cracks, delaminations, voids, and inclusion located beneath the sur- face. Acoustic microscopy is particularly suited to study this phenom- enon because it can image microscopic subsurface features without sectioning. Furthermore, it has been revealed that the velocity and at- tenuation of the leaky surface wave can be measured; these are ex- pected to have close correlation with the mechanical properties of ma- terials. New results on the nondestructive observation of subsurface cracks of Si,N, and ZrO, and delamination of TIN coatings introduced by Vickers indentation or sliding contacts are presented. The mecha- nism of delamination and wear of these materials is discussed. It is shown that the velocity and attenuation of the leaky surface wave of TIN coatings and sintered AlzOn actually have close correlation with the hardness and wear resistance of these materials. The reason for these correlations is also discussed.

Acoustic Microscopy of Ceramic Surfaces

The inspection of the sliding surface and subsurface of plasma-sprayed ceramic coatings using scanning acoustic microscopy

A refractory ceramic body having excellent bending strength and high hardness and with little porosity is obtained by sintering a powdery mixture comprising 5 to 95% by weight of a titanium carbonitride and 95 to 5% by weight of a metal boride such as metal diborides, e.g. titanium diboride, W2 B5 and Mo2 B5 at a temperature of 1700° to 1800° C. Further improvements can be obtained by partial replacement of the above mentioned components with elementary boron, titanium carbide or titanium nitride or when the titanium carbonitride component is a combination of at least two kinds of titanium carbonitrides having different chemical compositions relative to the proportion of the carbon and nitrogen.

Sintered ceramic body containing titanium carbonitride

The fracture toughness of structural materials are largely influenced by small flaws near the surface such as cracks, pores and inclusions. They had not been extensively investigated so far, because the observation technique has not been established. In this work, we describe two types of new applications of scanning acoustic microscope to the study of fracture and wear. First, detailed features of subsurface cracks in silicon nitride were observed and a new method to estimate the fracture toughness is proposed. It is also proposed that the measurement of attenuation of the leaky surface acoustic wave (leaky SAW) can be used to characterize the surface of steels with various heat treatment.

Application of Scanning Acoustic Microscope to the Study of Fracture and Wear

Caompatibility of ceramics with oils.

Characterization and study of the mechanical property of titanium nitride films were conducted using the imaging and measurement modes of acoustic microscopy. T he films were characterized by the velocity of leaky surface acoustic waves on the samples. Velocity increase due to the film n ormalized by the thickness of the film a nd the angular frequency of the acoustic wave was found to have a good correlation with the Knoop hardness of the film. It was found from observations of acoustic i mages that delaminations are introduced between two adjacent Vickers i ndentations o n TIN film d eposited o n a steel when the adherence of the film is poor. The ease to make such delaminations was found to provide a measure of the adherence of the film. It was also f ound from a coustic images of wear tracks on the film after repeated sliding contacts that a train of micro delamination cracks are introduced a nd coalesce i nto a long delamination crack. The influence of the residual stress due to the plastic indentation upon the initiation and propagation of the delamination is discussed.

Y. Tsuya

Papers

Acoustic Microscopy of Ceramic Surfaces

Sintered ceramic body containing titanium carbonitride

Application of Scanning Acoustic Microscope to the Study of Fracture and Wear

Caompatibility of ceramics with oils.

Acoustic Microscopy of Ceramics Coating for Tools and Sliding Elements of Machines