Do You Shave Before or After Your Shower? How Does It Affect Your Blade Life?

July 2021

People may have their own morning rituals. One routine many men are familiar with would be shaving their facial hair. Do you shave before or after taking shower? Let us have a closer look at the shaving blade and how it interacts with the skin and hair.

Note that modern blades are made of martensitic stainless steel that were quenched and tempered to a very high hardness and often coated with multiple layers of hard ceramic coatings (sometimes with diamond or diamond like carbon on top). However, even the hardest material coatings do not totally prevent wear. During shaving operations, the blade edges wear due to sliding, abrasion and plastic deformation. 

Before a shower, the skin is dry and may contain dust and other particles which could act as abrasives. When the shaving blade slides over the skin it exfoliates the dry skin and cuts the hair. The dirt and other foreign particles also come in contact with the cutting edge of the blade. The hair is also dry and has higher strength. Therefore, the blade has to work little harder to cut the hair 

The shaving blade wears due to all three mechanisms – abrasion, sliding and plastic deformation. When you shower and then shave, you not only get rid of the dust (abrasives) but also soak the hair. When the hair receives moisture, it becomes soft and therefore cutting is much easier. 

The bottom line is that it is better to shave after having shower. Your shaving blade will last much longer and you may also experience less skin irritation.

Can Diamonds Solve Your Wear Problems?

April 2021

Materials lose their usefulness due to breakage, wear or corrosion. Let us focus on wear here. Severe wear limits the use of equipment and tools used in mining, construction and road maintenance industries. When these metallic parts come in contact with the ground, they undergo severe abrasive wear. To increase their working life, often materials with very hardness are considered. 

Diamond is the hardest material known to humans and there are many attempts to use diamond in such situations. Diamond, a cubic form of carbon, can either be applied as a coating or mixed with a metallic binder (matrix) to form a composite material. 

There has been extensive testing on the applications of diamonds as wear coatings. One such attempt resulted in no significant increase in wear life compared to the current technology where tungsten carbide particles are used in a matrix of steel. 

Diamond is a great material but the diamond particles embedded in a metallic matrix was not fully utilized. A detailed study showed the metallic binder wore away leaving the diamond particles standing proud of the surface which were easily knocked by the moving rocks. This is very similar to a great knife held by a weak hand! If the diamond cannot be held in its place due to a rapid wear rate of the matrix, they will be lost.

The hardest materials do not necessarily mean they are suitable for any extreme wear applications. There are many factors to consider when choosing the correct materials or combination of materials for a particular purpose.

Corrosion Inhibitor Vendor Was Not Happy!

January 2021

One day, I was called in to investigate the uneven hardness of a steel product that was quenched and tempered to a specific hardness. After some preliminary investigation and interviews with the furnace operators, I found that the nozzles used in the spray quench area were blocked or spraying water sideways i.e. away from the steel product. Upon closer inspection, the nozzles were either plugged or had holes in the side. A simple metallurgical failure analysis revealed that the erosion of the nozzles occurred due to the oxide scale particles carried in the quench water. The same oxide scale in the quench water often blocked the water in some nozzles. 

The nozzles were made of austenitic stainless steel. A corrosion inhibitor was routinely added to the water to prevent corrosion of the pumps, nozzles and other equipment related to the quenching system. I was surprised when I was told that corrosion inhibitor was mainly needed to stop the corrosion of nozzles. 

It was recommended that nozzles be made of more wear resistant martensitic stainless steel, with a twin-tank to filter out the oxide scale in the quench water, and stop using any corrosion inhibitor. The vendor who supplied the corrosion inhibitor for over 20 years was not happy!

Customer Complaint Does Not Always Mean Materials Problems

October 2020

Once, a sales manager walked into my office and told me that a large customer had some quality issues with our products. They complained about uneven hardness in a heat treated steel product. As always, I asked for a defective product for analysis. A sample piece was received and metallurgically analyzed. We found that there was no problem with the product except some acceptable variations in hardness from location to location. These types of variations were acceptable for larger parts. 

A final report was produced and forwarded to the sales manager for distribution to the customer who complained about the defective product. After the meeting, I asked the sales manager how it had gone with the customer. What he told me was a total surprise. The customer did not even care about the hardness variations as he was more interested in getting price reduction rather than an improvement to the quality. 

When tooth wear life is improved, fatigue becomes a problem!

July 2020

A leading manufacturer of ground engaging tools experienced what appeared to be a routine failure of a tooth point in a mining operation. But a thorough failure analysis painted a different picture. It was a rare case failure due to fatigue.

The broken tooth from a customer was received in the lab for analysis. The fracture surface was cleaned and observed in a stereoscope for any macroscopic features. A portion of the fracture containing what appears to be the fracture origin was further analyzed using a scanning electron microscope. Chemical composition was determined using a spectrometer. Hardness was measured to confirm the specification. The microstructure was tempered martensite confirming a proper heat treatment. Then why did the tooth fail in service?

A casting defect was present at the crack origin. The fit between the tooth and the adapter was slightly loose resulting a cycling loading of the tooth. Once the fatigue crack reached a certain size, the remaining cross section of the tooth could not bear the applied load and failed in a catastrophic manner. This was a rare case of fatigue failure which occurred before the tooth was worn out!