A cutting element comprises a supporting substrate, and a cutting table attached to an end of the supporting substrate. The cutting table comprises inter-bonded diamond particles, and a thermally stable material within interstitial spaces between the inter-bonded diamond particles. The thermally stable material comprises a carbide precipitate having the general chemical formula, A3XZn-1, where A comprises one or more of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ac, Th, Pa, and U; X comprises one or more of Al, Ga, Sn, Be, Bi, Te, Sb, Se, As, Ge, Si, B, and P; Z comprises C; and n is greater than or equal to 0 and less than or equal to 0.75. A method of forming a cutting element, an earth-boring tool, a supporting substrate, and a method of forming a supporting substrate are also described.