Measuring & Reporting Friction Coefficients/Abrasion Resistance of Organic Coatings by Falling Abrasive/Dry Sand Rubber Wheel/Wet Sand Rubber Wheel/Scratch Tester/Galling Tester/Pin On Disk/Friction Tester/Amsler Twin Disk/Crossed Cylinder/Falex Block-on-Ring/Taber Abrasion Tester/Dry Erosion Tester/Wet Erosion Tester/Calo Tester/Hall-Danks Casing Wear Tester/Extreme Pressure & Lubricity Tester/Coating Adhesion Tester/FEI Quanta 200 Scanning Electron Microscope/Olympus DSX510 Digital Metallograph - Olympus PME Optical Metallograph
This test is a tilting-platform static friction coefficient type instrument that slowly increases the angle of tilt until the moveable sample breaks free and begins to slide. The tangent of the angle when sliding began is the coefficient of friction between the moveable (upper) and stationary (lower) specimens. Generally static (or starting) coefficient of friction is greater than the kinetic (moving) coefficient of friction.
(These test methods cover the determination of the resistance of organic coatings to abrasion produced by abrasive falling onto coatings applied to a plane rigid surface, such as a metal or a glass panel.)
This test method is a relatively low stress abrasion test originally intended for but not restricted to paints and similar organic coatings. Because a very wide variety of abrasive types and sizes can be used, and the test can be used to quantify the abrasive resistance of an extremely diverse range of coating types.
During this test an abrasive material (purified silica sand) is introduced between the specimen and a rotating rubber wheel in order to subject the specimen to constant wear as the abrasive is pulled between the rubber surface and the surface of the specimen. This is what is known as a low stress abrasion test, meaning the abrasive sand is not fractured during the test. The specimen is held in contact with the rubber wheel under a constant load and the sand flows at a constant rate. The value of this test lies in its ability to rank the relative wear resistances of materials by comparing the volume lost during testing.
Testing times vary according to the type of material being tested, but can range between 30 seconds and 30 minutes. Test specimen dimensions are rectangular prisms approximately 1” x 3” x 0.12-0.50” (25 mm x 76 mm x 3.2-12.7 mm)
This testing environment for this test is purified silica sand/ water slurry. During this test a specimen is held under constant load against the surface of a rotating rubber wheel. The silica sand is pulled between the rubber surface and the surface of the specimen. This is what is known as a low stress abrasion test, meaning the abrasive is not fractured in the contact zone. The value of this test lies in its ability to rank the relative wear resistances of materials by comparing the volume lost during testing.
Testing time is approximately 25 minutes. Test specimen dimensions are rectangular prisms approximately 1”x 2.25” x 0.25 - 0.625” (25 mm x 57 mm x 6.4 - 15.9 mm).
The scratch test reduces the abrasive wear mechanism to its simplest form, a single scratch. A diamond indenter is pressed into a test specimen and the test specimen is moved horizontally. Scratches are quantified in terms of depth, cross section or volume and general morphology (e.g. ductile plowing or brittle spalling). A scratch is sometimes made across two or more surface treatments so the difference between the two materials can be compared directly.
This test method is designed to rank material pairings with respect to galling resistance. A compressive load is applied to two clean specimens (with flat surfaces and a specific area of contact) and one specimen is rotated 360° relative to the other. The two surfaces are then visually examined for any galling damage. If no material transfer is obvious, a new set of specimens is tested at an increased load. This process is continued until galling is observed on the material surfaces. The greater the galling threshold pressure, the greater the galling resistance of the material couple.
The pin-on-disk wear machine is a common wear test rig because it is so versatile. As the name indicates, a pin slides on a horizontally-oriented rotating disk. The test specimens can be identical or different metals or non-metals, the surfaces can be dry or lubricated or the disk can be coated with a wide variety of abrasives. Sliding speed is controlled by rotational speed and sliding path diameter. Contact pressures are controlled by applied load and pin diameter.
This test is used to simulate adhesive and two and three body abrasive situations.
Friction testing is used to quantify the resistance to sliding between two components. A variety of materials and conditions can be evaluated including dry metal-on-metal, lubricated (e.g. oil or water) or specific materials on abrasive surfaces. Any material from which specimens can be fabricated can be used in this rig.
A typical specimen size is ½” x ½” x ¾” (12 mm x 12 mm x 18 mm). Testing variables include sliding speed, applied load, contact pressure, materials and surface conditions. The test has been used for oil well materials and manufacturing situations like polymer processing equipment.
The Amsler twin disk machine is a versatile test platform that can produce pure sliding or pure rolling (synchronized roller surface speeds) and any mixed rolling/sliding ratios in between. Specimens are typically approximately 1.5” (35 mm) in diameter and ½” (12 mm) wide. One specimen can also be a stationary block like the block-on-ring configuration. Abrasives or lubricants can be added to the contact zone or the rollers can be run with clean, metal-on-metal contact.
This rig has been used to simulate railroad rail-on-wheel couples (lubricated and dry, running and gauge surfaces), heavily loaded mining components and rolling contact fatigue (lower load, longer running time) situations.
The crossed cylinder configuration is a common format with simple sample geometry typically used for higher contact pressures between metal pairs. The cylinders are usually oriented horizontally and one is loaded and rotated on the other. Contact pressures are controlled by applied load and cylinder diameter.
In addition to testing specific metals, this type of machine can be used with various coatings applied to surfaces.
The block-on-ring is another versatile, simple specimen test. One specimen (ring) is rotated against a stationary block of same or dissimilar materials. Loads, specimen dimensions (width, diameter) and rotational speed are all used to determine operating parameters (e.g. contact pressure) and test severity.
There are several different types of Taber test machines but the most common format is twin abrasive disks spinning against a rotating, horizontally oriented test specimen. The abrasive disks, mounted vertically, are offset from the disk center of rotation. Loads are relatively light (grams) and can be varied to suit the application. A wide variety of abrasive disks can be used the machine.
Taber testers are typically used to test polymer hazing resistance and paint and coatings wear resistance.
Erosive wear refers to surface damage caused by the impingement of materials, solids, liquids or gases, often carrying abrasives, onto a component surface. This erosion tester uses compressed gas to transport many different types of abrasives. The abrasives are precisely metered by a powder feeder and particle velocity is measured with the spinning twin-disk method. The attack angle can be anything between 0 and 90o. Wear rates are usually reported in mass loss per mass flow rate of the abrasive.
The wet erosion test machine consists of a slurry pump, flow sensor, test chamber with specimen holder, associated piping and a logic controller that regulates the compressed air supply to the pump (Figures 1-4). The standard slurry is composed of a 1:10 ratio of AFS 50-70 silica sand and potable water. The slurry is re-circulated through a piping loop via a mixing tank/reservoir and emitted in a high-speed jet at an average velocity of 16 m/s.
Wear metric is mass loss per mass flow rate during testing.
The Calo Tester may be used to determine the abrasive wear resistance of thin coatings. During testing, a steel sphere is rolled against the coating with diamond paste applied to the surface of the coating. Wear resistance is measured in terms of depth of wear scar during a set time period.
An optical microscope may be used to determine the thickness of the coating after the coating has been worn through to the base material.
The HD CWT is used to evaluate the wear performance of well casing and tool joint hardbanding pairs. The test produces data on the severity of wear between the two components that can be correlated to their performance in a downhole application.
Testing parameters are controlled to promote the formation of wear mechanisms that occur in downhole environments. The test was designed to produce data that can be correlated with the relative wear performance of materials tested in the DEA42 casing wear test and actual downhole performance.
Determines the lubricating quality of drilling fluids and predicts wear rates of mechanical parts in fluid systems.
Measures adhesion (bond strength) of coatings to metal and other rigid substrates. Conforms to ASTM D4541/D7234.
FEI Quanta 200 Scanning Electron Microscope with light element Energy Dispersive Spectroscopy (EDS).
An Olympus DSX510 Digital Metallograph and an Olympus PME Optical Metallograph