From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
The experimental results of using carburised Hykro for case hardened materials.
| Identifier | ExFiles\Box 142\4\ scan0181 | |
| Date | 11th November 1936 | |
| Redex [REDACTED] [REDACTED] Talbot. [REDACTED] Pendlebury. [REDACTED] [REDACTED] [REDACTED] [REDACTED] 1203 HY.{Tom Haldenby - Plant Engineer}3/9.11.11.36. [REDACTED] GRY{Shadwell Grylls} Swoll CASE HARDENED MATERIALS. RE: USE OF CARBURISED HYKRO AS DISTINCT FROM NITRIDED HYKRO. The preliminary experiments we put in hand to satisfy ourselves as to the general suitability of Hykro material for carburised and hardened parts have been concluded, and I can issue the following information :- (1). In a completely hardened condition whether notches are present or not, the material fails under a sharp blow or as one might put it more graphically it is notch brittle without even a notch being present, this, of course, is where it has been carburised all over in the form of a bar. (2). The core of the material, although notch brittle when a hardened surface is present, is not notch brittle when the hardened surface has been removed. It will then give an impact value of 38 ft. lbs., the ultimate tensile under these conditions is 92 Tons, the elongation is 15%, reduction in area 40%, and the brinell of the core 429. (3). Brinell figure (V.F.N.) for the carburised and hardened surface lies between 875 and 940, the higher figures being obtained after removing .002 of the skin by polishing. (4). Cloudburst hardening. The above pieces by the Cloudburst process and aged 3 days give a brinell hardness (V.F.N.) of 1071. (5). A long bar was carburised and quenched in the usual manner. An attempt was then made to stretch the shaft to remove the distortion of .015. After grinding the case away it was found that the bar had cracked circumferentially about 18" from one end of the bar. When S2NCR was similarly treated no cracks were found after grinding away the hardened surface. The length of the bar in each case was 3 feet. | ||