D	diameter of a single spherical particle (μm)
D 32	Sauter average diameters of particles (μm)
E′	effective elastic modulus, which is defined by Equation (3) (GPa)
EM	erosive weight-loss of the boronized coating (mg·h−1)
Ep	elastic modulus of particles (GPa)
Et	elastic modulus of coating (GPa)
Ee	elastic potential energy during impact, which is defined by Equation (4) (J)
Em	kinetic energy of the particle, which is defined by Equation (5) (J)
F	contact force during the normal impact, which is defined by Equation (2) (N)
H	micro hardness of the target (GPa)
P	impact stress generated during the particle impingement, which is defined by Equation (8) (GPa)
Rp	radius of the incident particle (μm)
KC	fracture toughness of coating (MPa·m1/2)
V	velocity of the incident particle (m·s−1)
d p	diameter of quartz sand particles (μm)
h	indentation depth in the impingement process (μm)
h max	maximum indentation depth during the impingement process (μm)
l	initial defect length, which is assumed between 0.1−1 μm (μm)
m	mass of the incident spherical particles (g)
mp	cumulative mass of erodent particles (g)
m 1	mass of target before erosion test (mg)
m 2	mass of target after erosion test (mg)
q	mass flow rate of the incoming particles per unit time (kg·h−1)