Every material used for motorcycle exhaust qualifies as best based on its nature-given features and scientific suitability. Titanium, stainless steel, and Inconel are high-spec materials with unique characteristics, suitable for use according to chemical stability, toughness, weight, and heat resistance.
Here, we will explain these different materials for their primary features, uses, and mode of production to make the differences between stainless steel, titanium, and Inconel apparent.
Known for its high-standing strength-to-weight ratio, this metallic element is highly functional for low weight applications such as racing bikes. Titanium weight is half that of steel, but they are at par when it comes to strength. Titanium is more pricey than steel and aluminium but less expensive than Inconel.
Under atmospheric temperature, there's no reaction between titanium, moisture, and oxygen. Both titanium and Inconel are alike in material protection as they develop a protective passive oxidation surface layer over the material. Thus the reason for the potent anti-corrosive property of titanium. Even in the face of hydrochloric and sulphuric acid, titanium is resistant!
In addition, titanium cools down rapidly, so when used for motorcycle components like exhaust, it won't deform under so much heat.
There's pure commercial titanium and alloys of titanium on the market. The most standard titanium alloy manufactured using vanadium and aluminium is the Ti 6AI-4V. This makes up half of the titanium in the application worldwide. Compared to pure titanium, these versions have more strength toughness and can be easily machined. While highly corrosion-resistant, commercially pure titanium is more flexible and plastic than its alloy counterparts.
Complex hardening is also experienced with titanium, making it hard to machine. The pure commercial titanium is gummy and, when cut, develops lengthy chips that can disrupt cutting tools. This is why falling also happens during titanium machining. But with high-pressure coolant, chips can be cleared while cutting, and the devices can move more readily, thus lowering the difficulty involved.
Short, intermittent cuts should be avoided when machining titanium; the cutting tool should keep working when it meets the raw material. Rubbing is possible with too much tool contact, which forms too much heat that causes work hardening. Less speed a high feed rate style of machining will reduce heat formation.
A rigid machine setup and safe grip are required to machine titanium raw materials. Why? Titanium and titanium alloys are highly ductile, giving rise to chatter and spring back while being cut and may bring about a less-impressive surface finish.
It's easy to weld titanium and alloys of titanium. The same welding technique used on stainless steel applies to titanium.
But here, neatness and protection from inert gas are essential. Air contamination can make titanium welding go wrong.
Uses of titanium
The aerospace and automotive industry use titanium based on its impressive strength-to-weight ratio. 50% of alloys applied in aerospace engineering is the Ti 6AI-4V. Motorcycles use titanium for exhaust because of its lightweight, heat management, and availability in beautiful colours.
Titanium works for:
- Naval ships
- Sports equipment
- Medical industry
- Landing gears
- Missiles, etc
Super quality nickel-chromium alloys have a trading name called Inconel. This material can also withstand high temperatures (up to 2,000°F) following the type of alloy with zero strength loss. Even at low temperatures, this material is very suitable.
The mechanical features of Inconel at room temperature is superb. So that you know, Inconel 725 grade has a tensile strength of about 180 ksi; this is double the strength of structural steel. Other alloys like Inconel 718 are toughened to withstand precipitation, making them stronger. Corrosion and its cohorts: putting, oxidation, corrosion cracking and crevice corrosion don't impact Inconel.
Demanding applications are met with the excellent properties of Inconel. But, a material like Inconel is pricier than titanium, stainless steel and aluminium.
Because of its high strength, machining is challenging. Inconel is so hard that cutting tools get damaged during machining, and the material can twist and bend.
Dipping Inconel in a solution can reduce the material's hardness and save cutting tools from wearing. To machine Inconel, the recommendation is ceramic tools as it offers a rapid and non-stop cutting, ng which makes the work process more manageable. Pecking should be avoided as it makes the work challenging.
Due to cracking, Inconel is not easy to weld. But alloys of Inconel can be welded like the Inconel 625 - a fillquicklyal easily and typically welded with inert tungsten gas (TIG). This welding technique usually does not need a filler but works very well to join Inconel. That's why it's recommended.
Uses of Inconel
Where severe temperature and corrosion will be a problem, Inconel is a choice material, particularly when other metals fail to resist oxidation and deformation caused by the intense temperature.
Inconel has excellent temperature and chemical resistance and is useful for race bikes, turbines, the exhaust system of jet engines, and in the oil and gas, aerospace and marine sectors where heavy machine components are in demand.
Stainless steel is strong, non-magnetic, and stable in thermochemistry. This is a material that excels in ease of manufacture and affordability. The stainless steel 304 grade is the industry standard for manufacturing exhaust. The 304 grade stands tall in its application for affordable bike exhausts that have high performance and lasts long.
Unlike titanium,m whose high cost doesn't allow mass production of the motorcycle exhaust system, steel is relatively cheaper and in everyday use. Steel is more affordable than Inconel. But steel is heavier than titanium and has a low tensile strength, unlike Inconel, whose strength is very high. This is why it's limited in use for manufacturing functional exhaust parts. And as for sound, steel's thick walls produces quite a dull exhaust note compared to titanium. That sounds metallic!
Again, steel is anti-corrosive and very strong. Most of the time, the head pipes of dirt bikes are made from stainless steel.
Machining stainless steel
Some stainless steel grades are easier to machine than others, depending on the alacceptableineral content. In general, austenitic stainless steel is regarded as hard to machine. It's simple to machine 400 series of steel than the 300 series, including grades 304 and 316. Grade 303 is the most machinable stainless steel. Grade 316 steel is challenging and requires special cutting tools.
The addition of selenium and sulphur makes it easy to machine stainless steel. But this exposes the raw material to corrosion and disrupts welding.
Welding stainless steel
The less carbon content steel possesses, the easier its weldability is. The highest allowable carbon content for grade 304 stainless steel is 0.08%, while grade 304L contains up to 0.03% carbon.
Uses of stainless steel
The high strength, anti-corrosion, mechanical efficiency, and affordability of stainless steel make it suitable for mass production of motorcycle exhausts and in the food, construction, medical, and marine industry.