Editing Wankel engine (section)

===Materials===
As formerly described, the Wankel engine is affected by unequal [[thermal expansion]] due to the four cycles taking place in fixed places of the engine. While this puts great demands on the materials used, the simplicity of the Wankel makes it easier to use alternative materials, such as exotic alloys and [[ceramic]]s. A commonplace method is, for engine housings made of aluminum, to use a spurted [[molybdenum]] layer on the engine housing for the combustion chamber area, and a spurted steel layer elsewhere. Engine housings cast from iron can be induction-brazed to make the material suited for withstanding combustion heat stress.<ref name="Bensinger 1973 p. 137–138">{{cite book |last1=Bensinger |first1=Wolf-Dieter |title=Rotationskolben-Verbrennungsmotoren |place=Berlin, Heidelberg, New York |date=1973 |isbn=978-3-540-05886-1 |oclc=251737493 |language=de |pages=137–138}}</ref>

Among the alloys cited for Wankel housing use are A-132, Inconel 625, and 356 treated to T6 hardness. Several materials have been used for plating the housing working surface, [[Nikasil]] being one. Citroën, Daimler-Benz, Ford, A P Grazen, and others applied for patents in this field. For the apex seals, the choice of materials has evolved along with the experience gained, from carbon alloys, to steel, [[Ferritic stainless steel|ferritic stainless]], Ferro-TiC, and other materials.<ref name="Bensinger 1973 p. 93">{{cite book |last1=Bensinger |first1=Wolf-Dieter |title=Rotationskolben-Verbrennungsmotoren |place=Berlin, Heidelberg, New York |date=1973 |isbn=978-3-540-05886-1 |oclc=251737493 |language=de |page=93}}</ref> The combination of housing plating and the apex and side seal materials was determined experimentally, to obtain the best duration of both seals and housing cover. For the shaft, steel alloys with little deformation on load are preferred, the use of Maraging steel has been proposed for this.

Leaded petrol fuel was the predominant type available in the first years of the Wankel engine's development. Lead is a solid lubricant, and leaded [[gasoline|petrol]] is designed to reduce the wearing of seals and housings. The first engines had the oil supply calculated with consideration of petrol's lubricating qualities. As leaded petrol was being phased out, Wankel engines needed an increased mix of oil in the petrol to provide lubrication to critical engine parts. An SAE paper by [[David Garside]] extensively described Norton's choices of materials and cooling fins.{{Citation needed|date=March 2023}}