UNITEST Scratch

The Scratch Testing Configuration

Damage and failure mechanisms of thin films and coatings under high contact stress can be unambiguously identified using the UNITEST - Scratch Configuration.

Its programmable, closed loop loading system can apply fixed, ramped, stepped or custom loading profiles. Interchangeable load heads give you the flexibility to start with one range, but to evolve as your needs grow. A variety of sensors like acoustic emission, humidity and temperatures are also available to add further insight to your evaluation.

Surface observation add-ons for 2D and 3D surface maps are also available. The data acquisition system can display the image and the test data in a single view for easy evaluation.

Technical Specifications

Platform

The platform can withstand loads of up to 2,000 N
Loading rate: 0.01 to 20 N/s
X-Y stage travel: 75 mm
Stroke: Up to 50 mm
Speed: 10 µm/s to 5 mm/s
Sample size (max): 60 x 60 x 10 mm (LxWxT)
Optical imaging: 4X, 10X, 20X, 100X objectives and total magnification up to 1000X
Acoustic emission: 150 kHz or higher
High Temperature: Up to 400 °C (system is capable of higher temperatures. Suitability depends on the material of stylus)
Environment: Lubricant, humidity

Test Standards

The UniTest Scratch is fully compliant with global standards for scratch testing. With test protocols embedded in the software, you can run tests in accordance with ASTM and ISO at the click of a button. This means less user training requirements, fewer errors, and lower costs of operations.

ASTM C1624: Standard test method for adhesion strength and mechanical failure modes of ceramic coatings by quantitative single point scratch testing.
ASTM D7027: Standard test method for evaluation of scratch resistance of polymeric coatings and plastics using an instrumented scratch machine.
ISO 20502:2005: Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of adhesion of ceramic coatings by scratch testing.
ISO 27307:2015: Thermal spraying — Evaluation of adhesion/cohesion of thermal sprayed ceramic coatings by transverse scratch testing.

Reference Materials

BCR 692 PACVD diamond like carbon coating with Ra of 0.01 micron
Verified cohesive and adhesive failure loads
Source - Institute of Reference Materials and Measurements, IRMM, Belgium

Tips

Rockwell C diamond stylus, 120 degree and 200 micron radius
Verified using non contact profilometry

Applications

Determination of critical load for hard and brittle coatings like titanium nitrides, boron nitrides, diamond
like carbon, etc.
Single particle scratch resistance behaviour of antireflective coatings and its comparison with erosion.
Estimation of bond strength at substrate – coating interface.
Product development and quality control of surface engineered product.
Scratch resistant behaviour of dental materials in physiological and corrosive environment. Check out our latest article on In situ scratch analysis of BCR 692 using Unitest

Load, Traction, Acoustic and Depth Sensors

Interchangeable force sensors mounted on the moving cross head measure the normal and traction force simultaneously. A change in friction force may represent delamination in the coating. The wideband acoustic emission sensor with high sensitivity mounted on the stylus assembly picks up early damage events such as initiation of subsurface cracks. An inline depth sensor measures the penetration depth of the stylus into the material. Automation enables both pre and post test scan and software algorithms report the final true residual depth.

Multi-Axis Stage (X-Y)

A motorized platform with a bidirectional X-Y stage with long travel offers capability to control the length of scratch as well conduct multiple scratches with offsets. Precise step servo motors with embedded encoders allow for accurate repositioning of the sample between the mechanical head and optical head without backlash. This offers users the advantage to locate specific regions on their sample for conducting tests and imaging the same region post scratch/indentation.

"Ducom UniTest with Inline Imaging is a sophisticated instrument capable of characterization of surface response and damage of materials. In-situ imaging with scratch and indentation modes offers flexibility to probe specific regions of our material in a repeatable manner. Moreover the high resolution stitched images superimposed on the data from other sensors such as traction and acoustic emission provide insights into understanding of damage mechanisms. Such a facility will help us develop better coatings for a variety of applications."

Dr .Udaya Bhat
Professor in Metallurgical and Materials Engineering and Chairman, Central Research Facility, NITK Surathkal, India

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