Evaluation of Tests for Cermets as Components of Heat-Resistant Materials.

Specimens of one cermet composition for flexural tests were received. These specimens K 152B nominal composition of 70 titanium carbide - 30 nickel were substituted for K 162B nominal composition of 62 titanium carbide - 8 columbium - 25 nickel - 5 molybdenum. Equipment was designed for testing cermets in flexure at room temperature by 1 centerpoint loading with a ball, 2 midpoint loading with a cylinder, 3 two-point loading third point, and 4 two-point loading fifth point. Methods of aligning the supporting and loading bearings of the equipment have been incorporated into the design. Also, equipment was designed for transmitting deflection of cermets in bending to a Tuckerman optical strain gage for determining the modulus of elasticity. The equipment is now being fabricated. Arrangements were made for inspecting cermets of a given composition by comparing attenuation. The design of specimens for determining the tensile properties of cermets will depend, in part, on the results of two-dimensional stress patterns obtained from photoelastic studies. Stress patterns for models subjected to tension were obtained by use of a plane and a circular polariscope. The plane polariscope revealed lines showing the direction of the principal stresses isoclinics which are represented by dotted lines in figures 2,3, and 4. Figure 5A shows the stress pattern of a model with shouldered ends figure 1. The stress in the gage is 620 psi. Figure 5B shows the stress pattern of another model with shouldered ends figure 2 with a larger radius for its fillet and a stress in its gage of 485 psi.