The microindenter has proven to be a powerful device in the characterization of the mechanical properties of thin films. The machine has both high resolution in the applied load and penetration depth measurements, as well as the versatility to perform different types of testing. The former provides the capability to deal with extremely thin films, while the latter allows for other mechanical properties, in addition to hardness, to be acquired. Four types of tests, namely indentation, scratch, load relaxation, and indentation fatigue tests can currently be conducted using the microindenter via different operating procedures. Only the scratch and load relaxation techniques will be covered in this paper. In a microscratch test, the normal load, tangential load, scratch length, and acoustic emission are monitored simultaneously during an entire scratch process for the purposes of measuring the critical load and studying the failure mechanisms of the deposited films. The adhesion strength, scratch hardness, fracture toughness, and friction are the mechanical properties which are possible to obtain by using this technique. Results from aluminum, carbon, and zirconia coatings will be discussed. The load relaxation test provides information on the creep properties of the films and results in an empirical constitutive relation between the applied stress and plastic strain rate. The creep properties of DC sputtered Al films will be used as an illustration of this.

Microscratch and load relaxation tests for ultra-thin films

The adhesion of as-sputtered Pt thin films to NiO single crystals has been characterized by a continuous microscratch technique. In these experiments, a conical indenter was driven into a 1.2 μm thick Pt film at a rate of 15 nm/s, and across the sample surface at a rate of 0.5 μm/s, until a load drop was observed indicating that the film had delaminated. Using the width of the scratch track at the point at which the film delaminated from the substrate, the critical load required for delamination, and the area of the delaminated region, a model has been developed to determine the work of adhesion of the Pt/NiO system. This model uses an elastic contact mechanics approach to relate the stresses acting in a scratch experiment to the strain energy released during film delamination. Using this model, the work of adhesion and hence the interfacial fracture toughness have been determined to be 0.023–0.06 J/m2 and 0.07–0.11 MPa$\sqrt m$, respectively. These values are in reasonable agreement with those determined by other methods for metal-ceramic systems.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400016496

Microscratch analysis of the work of adhesion for Pt thin films on NiO

A study of the tribological behaviour of piston ring/cylinder liner interaction in diesel engines using acoustic emission

Metal-ceramic interfacial fracture resistance using the continuous microscratch technique

A storage device including a housing defining a controlled environment. A storage medium is mounted in the housing, with a liquid lubricant contained in the housing and disposed on the surface of the storage medium. A spindle motor is provided in the housing for rotating the storage medium. At least one read/write head is mounted on an actuator assembly, the assembly for positioning the read/write head with respect to the storage medium. Control electronics are coupled to the actuator, read write head, and spindle motor, for interacting with the actuator, head, and motor to read data from and write data to the storage medium. The device housing has a length of about four inches, a height of about five-tenths inch, and a width of about two and three-quarters inches. A wick is provided to recirculate and dispose the liquid bearing on the surface of the storage medium. The wick generally has a disposing portion, positioned adjacent each side of the storage medium, and a collection portion disposed within the housing. The collection portion collects fluids at all attitudes in which the storage device housing may be oriented.

Lubricated disk drive

Acoustic Emission (AE) technique is applied to the detection of slider-to-disk contact. The type of slider-to-disk contact is identified by detecting the AE caused by contact. Advantages of this method are simplicity of measurement and the ability to detect contact between slider and disk fabricated from any material. In addition, this method can be used to measure the projection height distribution over an entire disk surface, which is one of the most important factors governing the reliability of disk files.

K. Kogure

Papers

New method of detecting contact between floating-head and disk

Flying heads with sub-micron spacing for magnetic recording discs