SPECIALIST MOUNTING COMPOUNDS
Spectrographic offers a variety of hot compression mounting resins for encapsulation of polished samples. The most common and economical hot mounting resins are the phenolic resins (Bakelite). This type of thermosetting resin will suit most hot mounting applications and is available in two colours. In cases where better sample edge retention is required, the use of epoxy mounting compounds is recommended. Where samples are to be examined in an SEM, carbon conducting compound is advised. In applications where a transparent mount is desirable, an acrylic thermoplastic mounting compound is the resin of choice. A range of hot mounting compounds, give us a call to discuss the options +44 (0) 1943 879001.
This may seem to be an extra step in the process but it is essential to ensure good preparation of the metallographic sample and it can also save the ends of your fingers if you are using a manual grinding process.
Information on Mounting Process
Mounting is used to support a sample that is small or of irregular shape. There are a number of different mounting media that you can use, each having its own benefits and drawbacks. The mounting media will be chosen by historical use at your company, cost and number of samples that you are preparing.
Why do we need to mount samples?
Samples will require mounting if they
- Are small and difficult to handle
- Of irregular shape
- You need edge retention
- The sample is porous and brittle
- You use an automatic polishing machine that uses samples of specific sizes
- It is difficult to fully polish larger samples – mounting will assist in maintaining a flat surface especially when polishing by hand
- Requirements of the mounting media
- Must flow around sample
- Forms tight seal around sample to prevent ingress of polishing media
- Range of hardness to suit the grinding and polishing characteristics different materials
- Must be resistant to etchants eg. Diallyl Pthallate has better resistance to strong acids than Bakelite
- Quickly and easily processed to suit busy test house /laboratory
- The mounting material must form a tight seal around the sample to prevent ingress of grinding and polishing media into the gap.
- This can result in scratching of the sample on final polishing and staining due to the material exuding from the gap prior to examination.
- The relative thermal contraction of the sample and media can affect this with the greater thermal contraction of the resin giving a tighter seal
- The abrasion rate of the mount should be matched to that of the sample to prevent positive and negative relief.
- Particles of for example SiC or alumina can be added to a mount to increase its hardness
- The mounting media should assist in sample edge retention